US20050141148A1 - Magnetic memory - Google Patents

Abstract

It is possible to reduce writing current without causing fluctuation of the writing characteristic. A magnetic memory includes: a magnetoresistance effect element having a magnetization pinned layer whose magnetization direction is pinned, a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the magnetization pinned layer and the storage layer; and a first wiring layer which is electrically connected to the magnetoresistance effect element and extends in a direction substantially perpendicular to a direction of an easy magnetization axis of the storage layer, an end face of the magnetoresistance effect element substantially perpendicular to the direction of the easy magnetization axis of the storage layer and an end face of the first wiring layer substantially perpendicular to the direction of the easy magnetization axis being positioned on the same plane.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-402891, and 2004-244771 filed on Dec. 2, 2003, and Aug. 25, 2004 in Japan, the entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
• The present invention relates to a magnetic memory having a magnetoresistance effect element in a memory cell.
RELATED ART
• A magnetic random access memory (MRAM) is a memory device which uses a magnetoresistance effect element in a cell portion which stores information or data, to which attention is paid as the next generation memory device characterized by high speed operation, mass storage, and nonvolatile. The magnetoresistance effect is a phenomenon where when magnetic field is applied to a ferromagnetic material, an electric resistance varies according to direction of magnetization of the ferromagnetic material. Function serving as a memory device (MRAM) can be achieved by using the direction of magnetization of such ferromagnetic material for recording information or data to read the information according to the magnitude of an electric resistance corresponding to the direction of magnetization. In recent years, in a ferromagnetic tunnel junction including a sandwich structure where an insulating layer (a tunnel barrier layer) is interposed between two ferromagnetic layers, taking advantage of such a fact that a magnetoresistance change ratio (MR ratio) of 20% or more can be obtained owing to a tunnel magnetoresistance effect (TMR effect), an MRAM where a ferromagnetic tunnel junction magnetoresistance effect element (TMR element) utilizing a tunnel magnetic effect is used is expected and attractive.
• When the TMR element is used in the MRAM, one of the two ferromagnetic layers sandwiching the tunnel barrier layer is constituted as a magnetization pinned layer with direction of magnetization pinned so as not to vary, which is a reference layer, while the other ferromagnetic layer is constituted as a magnetization free layer with direction of magnetization easily reversed, which is a storage layer. Information or data can be stored by causing a parallel state where the directions of magnetization in the reference layer and in the storage layer are parallel to each other and an anti-parallel state where the both are anti-parallel to correspond to “0” and “1” of binary information. Writing of record information is performed by causing current to flow a writing wire provided near the TMR element to generate induced magnetic field and reversing the direction of magnetization in the storage layer by the induced magnetic field. Reading of record information is performed by detecting an amount of magnetoresistance change due to the TMR effect. Accordingly, it is preferable that the magnetoresistance change ratio (MR ratio) due to the TMR effect is larger and field required for magnetization reversing, namely, switching magnetic field is smaller in the storage layer. On the other hand, it is necessary to pin magnetization of the reference layer such that reversing of the magnetization hardly occurs. For this reason, such a method that an anti-ferromagnetic layer is provided so as to come in contact with the ferromagnetic layer so that magnetization reversing is made hard to occur due to an exchange coupling force is used. Such a structure is called “spin valve structure”. In this structure, the direction of magnetization in the reference layer is determined by conducting thermal treatment during application of magnetic field. (magnetization pinning anneal).
• As described above, the MRAM conducts magnetization reversing on the storage layer utilizing induced magnetic field generated by current flowing in a writing wire. However, magnetic field required for magnetization reversing, namely switching magnetic field becomes large according to fineness of the TMR element, which results in increase in amount of current flowing in the writing wire and, therefore, increase in power consumption. In order to solve the problem, a so-called “a wire with a yoke” constituted by covering a writing wire with soft magnetic material or the like to cause magnetic field generated from the writing wire to act on the TMR element efficiently (for example, refer to U.S. Pat. No. 5,659,499 and U.S. Pat. No. 5,956,267).
• Even if such a wire with a yoke is provided, magnetic field is actually concentrated on an end portion of the soft magnetic layer on the wire with a yoke. Therefore, in order to reduce writing current, such a constitution can be employed that the end portion of the soft magnetic layer on the wire with a yoke is positioned near the TMR element.
• However, it is difficult to manufacture an MRAM where a relative position between the end portion of the soft magnetic layer and the TMR element has been determined considering not only a deviation between the end portion of the soft magnetic layer and the TMR layer on a plane but also a deviation therebetween in a vertical direction which is a direction perpendicular to the plane. Further, a deviation in difference between the end portion of the soft magnetic layer and the TMR element appears as a difference in writing characteristic of the TMR element as it is, which causes some fluctuation in writing characteristic.
SUMMARY OF THE INVENTION
• The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic memory which decreases fluctuation in writing characteristic and allows reduction of writing current.
• Further, another object thereof is to provide a magnetic memory which allow mass storage and high speed writing.
• A magnetic memory according a first aspect of the present invention includes: a magnetoresistance effect element having a magnetization pinned layer whose magnetization direction is pinned, a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the magnetization pinned layer and the storage layer; and a first wiring layer which is electrically connected to the magnetoresistance effect element and extends in a direction substantially perpendicular to a direction of an easy magnetization axis of the storage layer, an end face of the magnetoresistance effect element substantially perpendicular to the direction of the easy magnetization axis of the storage layer and an end face of the first wiring layer substantially perpendicular to the direction of the easy magnetization axis being positioned on the same plane.
• A magnetic memory according to a second aspect of the present invention includes: a magnetoresistance effect element which has a magnetization pinned layer whose magnetization direction is pinned, a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the magnetization pinned layer and the storage layer, and whose film face shape has a long axis and a short axis; and a first wiring layer which is electrically connected to the magnetoresistance effect element, an end face of the magnetoresistance effect element extending along the short axis of the magnetoresistance effect element and a side face of the first wiring layer extending along a longitudinal direction of the first wiring layer being positioned on the same plane.
• A method for manufacturing a magnetic memory according to a third aspect of the present invention includes: stacking a magnetoresistance effect film which serves as a magnetoresistance effect element and comprises a first magnetic layer serving as a magnetization pinned layer whose magnetization direction is pinned, a second magnetic layer serving as a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the first magnetic layer and the second magnetic layer to serve as a tunnel barrier layer, and a wiring film serving as a wire; and patterning the magnetoresistance effect film and the wiring film such that an end face of the magnetoresistance effect element substantially perpendicular to a direction of an easy magnetization axis of the storage layer and an end face of the wiring film substantially perpendicular to the direction of the easy magnetization axis are positioned on the same plane.
• A method for manufacturing a magnetic memory according to a fourth aspect of the present invention includes: stacking a magnetoresistance effect film which serves as a magnetoresistance effect element and comprises a first magnetic layer serving as a magnetization pinned layer whose magnetization direction is pinned, a second magnetic layer serving as a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the first magnetic layer and the second magnetic layer to serve as a tunnel barrier layer and whose film face shape has a long axis and a short axis, and a wiring film serving as a wire; and patterning the magnetoresistance effect film and the wiring film such that an end face of the magnetoresistance effect element extending along the short axis of the magnetoresistance effect element and a side face of the wiring layer extending along a longitudinal axis of the wire are positioned on the same plane.
• A magnetic memory according to a fifth aspect of the present invention, which has memory cells, each includes: a storage element having a magnetic recording layer whose magnetization direction changes according to external magnetic field, a magnetization pinned layer whose magnetization direction is pinned, and a non-magnetic layer provided between the magnetic recording layer and the magnetization pinned layer; a writing wire which is provided on the opposite side of the magnetic recording layer from the non-magnetic layer and in which writing current flows; and a yoke which is provided on the opposite side of the writing wire from the magnetic recording layer, a pair of opposed side faces of the storage element being positioned on the same plane as a pair of opposed side faces of each of the writing wire and the yoke, and a relative magnetic permeability of the magnetic recording layer being 5 or more.
• A magnetic memory according a sixth aspect of the present invention, which has memory cells, each includes: a storage element having a magnetic recording layer whose magnetization direction changes according to external magnetic field, a magnetization pinned layer whose magnetization direction is pinned, and a non-magnetic layer provided between the magnetic recording layer and the magnetization pinned layer; a writing wire which is provided on the opposite side of the magnetic recording layer from the non-magnetic layer and in which writing current flows; and a yoke which is provided on the opposite side of the writing wire from the magnetic recording layer, a longitudinal axis of the magnetic recording layer being inclined to a direction perpendicular to a direction in which the writing wire extends by an angle of more than 0° and less than 90°, and a relative magnetic permeability of the magnetic recording layer being 5 or more.
• A magnetic memory according to a seventh aspect of the present invention, which has memory cells, each includes: a storage element having a magnetic recording layer whose magnetization direction changes according to external magnetic field, a magnetization pinned layer whose magnetization direction is pinned, and a non-magnetic layer provided between the magnetic recording layer and the magnetization pinned layer; a writing wire which is provided on the opposite side of the magnetic recording layer from the non-magnetic layer and in which writing current flows; and a yoke which is provided on the opposite side of the writing wire from the magnetic recording layer, a longitudinal axis of the magnetic recording layer being inclined to a direction perpendicular to a direction which the writing wire extends by an angle of more than 0° and less than 90°, and a pair of opposed side faces of the storage element being positioned on the same plane as a pair of opposed side faces of each of the writing wire and the yoke.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIGS. 1A and 1B are a plan view and a front view showing a constitution of a memory cell in a magnetic memory according to a first embodiment of the present invention;
• FIG. 2 is a schematic perspective view showing a constitution of the memory cell in the magnetic memory according to the first embodiment;
• FIG. 3 is a schematic sectional view showing a constitution of a TMR element used in the present invention;
• FIG. 4 is a graph showing a relationship between a film thickness on a wire and induced magnetic field generated from the wire;
• FIG. 5 is a sectional view showing a step of manufacturing the magnetic memory according to the first embodiment;
• FIG. 6 is a sectional view showing a step of manufacturing the magnetic memory according to the first embodiment;
• FIG. 7 is a sectional view showing a step of manufacturing the magnetic memory according to the first embodiment;
• FIG. 8 is a sectional view showing a step of manufacturing the magnetic memory according to the first embodiment;
• FIG. 9 is a sectional view showing a step of manufacturing the magnetic memory according to the first embodiment;
• FIG. 10 is a sectional view showing a step of manufacturing the magnetic memory according to the first embodiment;
• FIG. 11 is an electric circuit diagram showing a constitution of the magnetic memory according to the first embodiment;
• FIG. 12 is a schematic perspective view showing a constitution of a memory cell in a magnetic memory according to a second embodiment;
• FIG. 13 is a schematic perspective view showing a constitution of a memory cell in a magnetic memory according to a third embodiment;
• FIG. 14 is a sectional view showing a constitution of the memory cell in the magnetic memory according to the third embodiment;
• FIG. 15 is an electric circuit diagram showing a constitution of the magnetic memory according to the third embodiment;
• FIG. 16 is a schematic perspective view showing a constitution of a memory cell in a magnetic memory according to a fourth embodiment;
• FIG. 17 is a sectional view showing a step of manufacturing of the magnetic memory according to the fourth embodiment;
• FIG. 18 is a sectional view showing a step of manufacturing of the magnetic memory according to the fourth embodiment;
• FIG. 19 is a sectional view showing a step of manufacturing of a magnetic memory according to a fifth embodiment;
• FIG. 20 is a sectional view showing a step of manufacturing of the magnetic memory according to the fifth embodiment;
• FIG. 21 is a sectional view showing a step of manufacturing of the magnetic memory according to the fifth embodiment;
• FIG. 22 is a sectional view showing a step of manufacturing of a magnetic memory according to a sixth embodiment;
• FIG. 23 is a sectional view showing a step of manufacturing of the magnetic memory according to the sixth embodiment;
• FIG. 24 is a sectional view showing a step of manufacturing of the magnetic memory according to the sixth embodiment;
• FIG. 25 is a sectional view showing a step of manufacturing of the magnetic memory according to the sixth embodiment;
• FIG. 26 is a sectional view showing a step of manufacturing of the magnetic memory according to the sixth embodiment;
• FIG. 27 is a schematic perspective view showing a constitution of a memory cell in a magnetic memory according to a seventh embodiment;
• FIG. 28 is a sectional view showing a step of manufacturing of the magnetic memory according to the seventh embodiment;
• FIG. 29 is a sectional view showing a step of manufacturing of the magnetic memory according to the seventh embodiment;
• FIG. 30 is a sectional view showing a step of manufacturing of the magnetic memory according to the seventh embodiment;
• FIG. 31 is a sectional view showing a step of manufacturing of the magnetic memory according to the seventh embodiment;
• FIG. 32 is a sectional view showing a step of manufacturing of the magnetic memory according to the seventh embodiment;
• FIG. 33 is a sectional view showing a step of manufacturing of the magnetic memory according to the seventh embodiment;
• FIG. 34 is a sectional view showing a step of manufacturing of a magnetic memory according to a eighth embodiment;
• FIG. 35 is a sectional view showing a step of manufacturing of the magnetic memory according to the eighth embodiment;
• FIG. 36 is a sectional view showing a step of manufacturing of the magnetic memory according to the eighth embodiment;
• FIG. 37 is a sectional view showing a step of manufacturing of the magnetic memory according to the eighth embodiment;
• FIG. 38 is a sectional view showing a step of manufacturing of the magnetic memory according to the eighth embodiment;
• FIG. 39 is a sectional view showing a step of manufacturing of the magnetic memory according to the eighth embodiment;
• FIG. 40 is a sectional view showing a step of manufacturing of a magnetic memory according to a ninth embodiment;
• FIG. 41 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 42 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 43 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 44 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 45 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 46 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 47 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 48 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 49 is a sectional view showing a step of manufacturing of the magnetic memory according to the ninth embodiment;
• FIG. 50 is a sectional view showing a constitution of a memory cell in a magnetic memory according to a tenth embodiment;
• FIG. 51A is a sectional view showing a constitution of a memory cell in a magnetic memory according to an eleventh embodiment of the present invention;
• FIG. 51B is a sectional view of a constitution of a memory cell in a magnetic memory according to a twelfth embodiment of the present invention;
• FIG. 52 is a characteristic graph showing an average generation magnetic field generated in a magnetism closing circuit to a relative magnetic permeability of a yoke when a relative magnetic permeability of a magnetic recording layer is used as a parameter in the eleventh embodiment;
• FIG. 53 is a graph showing change of magnetization of a magnetic recording layer to application of magnetic field;
• FIG. 54 is a diagram showing a relationship between an easy axis of magnetization of the magnetic recording layer according to one embodiment of the present invention and applied magnetic field;
• FIG. 55 is a plan view showing an arrangement of a magnetic recording layer and a writing wire according to one embodiment of the present invention;
• FIGS. 56A to56D are views showing examples of a plan shape of a magnetic recording layer according to one embodiment of the present invention;
• FIG. 57 is a diagram showing a constitution of the magnetic memory according to a first example of the present invention; and
• FIGS.58(a),58(b), and58(c) are perspective views showing manufacturing steps in a method for manufacturing the magnetic memory according to a second example of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• Embodiments of the present invention will be explained below with reference to the drawings.
First Embodiment
• A magnetic memory according to a first embodiment of the present invention will be explained with reference toFIG. 1A toFIG. 11. A magnetic memory according to this embodiment has a plurality of memory cells arranged in a matrix array. A constitution of each memory cell is schematically shown inFIGS. 1A and 1B.FIGS. 1A and 1B are a plan view and a front view of a memory cell according to the embodiment, respectively.FIG. 2 is a perspective view of the memory cell according to the embodiment. The memory cell according to the embodiment is provided with aTMR element6, awriting wire4 for performing writing on theTMR element6, and ayoke2 formed of a magnetic layer. Thewriting wire4 is formed on theyoke2, and theTMR element6 is formed on thewriting wire4. Incidentally, a wire (not shown) used for reading is provided on theTMR element6.
• As shown inFIG. 3, for example, theTMR element6 has a stacking structure of alower electrode layer6a, a magnetizationfree layer6bconstituting a storage layer with variable direction of magnetization, a tunnel barrier layer6c, a magnetization pinned layer6dconstituting a reference layer with pinned direction of magnetization, and anupper electrode layer6e. Incidentally, in order to fix the magnetization pinned layer6dby an exchange coupling force, it is preferable that an anti-ferromagnetic layer (not shown) is provided between the uppermagnetic electrode layer6eand the magnetization pinned layer6d. In this embodiment, the magnetizationfree layer6bis formed below the magnetization pinned layer6dvia the tunnel barrier layer6c, but it may be formed above the magnetization pinned layer6dvia the tunnel barrier layer6c. The direction of the magnetization pinned layer6dand the direction of magnetizationfree layer6bare parallel or anti-parallel, but the directions of magnetization of the both correspond to a direction of an easy magnetization axis. The direction of the easy magnetization axis of the magnetization pinned layer6dand the magnetizationfree layer6b, namely, a direction of an easy magnetization axis of theTMR element6 is indicated with arrow inFIG. 2.
• On the other hand, a direction of an easy magnetization axis of theyoke2 corresponds to a longitudinal direction thereof and it is perpendicular to the direction of the easy magnetization axis of theTMR element6, as shown inFIG. 2.
• In the embodiment, as shown inFIGS. 1A and 2, such a constitution is employed that anend face6A of theTMR element6 perpendicular to the easy magnetization axis thereof, and end faces4A and2A of thewriting wire4 and theyoke2 which are parallel to the longitudinal directions of thewriting wire4 and theyoke2 and are perpendicular to their easy magnetization axes are positioned substantially on the same plane.
• In the embodiment, induced magnetic field generated from thewriting wire4 is concentrated on theend face4A of thewriting wire4, and theend face4A of thewriting wire4 and theend face6A perpendicular to the easy magnetization axis of theTMR element6 are positioned substantially on the same plane. For this reason, regarding a plurality of memory cells, a relative positional deviation in a plane direction between thewriting wire4 and theTMR element6 is not present principally. Since a distance fluctuation in a direction of film thickness between theend face4A of thewriting wire4 and the storage layer6B f theTMR element6 depends on only the film thickness of the stacked layer present therebetween, such a fluctuation can be reduced by selecting a proper film forming process. In a recent sputtering apparatus for TMR element production, it is a common practice to guarantee a film thickness distribution within a plane of an 8-inch substrate in ±1% or less. Accordingly, writing characteristic on a plurality of memory cells can be prevented from fluctuating.
• FIG. 4 is a characteristic graph showing a wiring film thickness dependency of induced magnetic field generated at a central portion of theTMR element6 from thewriting wire4 when a writing current is maintained at a fixed value. Regarding the thickness of thewiring layer4, as understood fromFIG. 4, when thickness sizes of both a wire with no yoke and a wire with a yoke are reduced down to 50 nm or so, induced magnetic fields in the both become large.
• It has been found that, when a wire with a yoke is employed, a current value at which magnetization of thestorage layer6bin theTMR element6 is actually reversed is deviated from the graph according to thinning of the wire film thickness. Such a phenomenon is not elucidated sufficiently at present, but the following two reasons may be considered as the cause thereof.
• (a) Since themagnetic layer4 of the wire with a yoke and the storage layer in theTMR6 are close to each other, when the magnitude of the induced magnetic field applied to only the end of theTMR element6 exceeds the magnitude of the switching field, the magnetization is wholly reversed at a stroke.
• (b) A magnetic resistance of theyoke2, theTMR element6, and a magnetic circuit formed of theyoke2 becomes small, so that magnetic flux larger than that obtained when it is assumed that the TMR element is a complete non-magnetic layer is generated.
• In the magnetic memory according to the embodiment, the above effect or advantage was noticeable when the wiring layer film thickness is experimentally set to 50 nm or less. However, it is preferable for achieving a sufficient effect or advantage that the film thickness is set to 30 nm or less.
• In the magnetic memory according to the embodiment, since the easy magnetization axis of theyoke2 and the easy magnetization axis of theTMR element6 are perpendicular to each other, any magnetic interaction between the both is not present in a state where current does not flow in the wire. Therefore, magnetic disturbance due to theyoke2 to theTMR element6 is not generated.
• The magnetic memory according to the embodiment is suitable for fineness. This is because a lower electrode larger than theTMR element6 is used in an ordinary MRAM structure, and a cell size in an MRAM generally depends on the size of the lower electrode. In the embodiment, since the lower wire serves as thelower electrode6atoo, the cell size can be reduced.
• TheTMR element6 is a tunnel junction type magnetoresistance element including at least one magnetization pinned layer, at least one magnetization free layer (a storage layer), and a tunnel barrier layer sandwiched between the magnetization pinned layer and the magnetization free layer, and it is unnecessary to specify the order of stacking of the storage layer and the magnetization pinned layer.
• General material with high magnetic permeability, such as soft ferrite including Fe, Fe—Al alloy, Fe—Si alloy, or such Fe—Si—Al alloy as Sendust as a main ingredient, or amorphous alloy of Fe, Co, Ni and B, Si, P, or the like is suitable as magnetic material used for theyoke2. It is preferable that the magnetic material has relative magnetic permeability of 10 or more, and it is important to meet the following expression in order to perform writing on the TMR element. Magnetic permeability of theyoke2×the film thickness of theyoke2>the magnetic permeability of the magnetizationfree layer6b×the film thickness of the magnetizationfree layer6b.
• As described above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
• Next, a method for manufacturing the magnetic memory according to the first embodiment will be explained with reference toFIG. 5 toFIG. 10. As shown inFIG. 5, first, a driving circuit for an MRAM and the like are formed on a lower layer, and ayoke2 with a film thickness of 10 nm made of Ni—Fe and awriting wiring layer4 with a film thickness of 20 nm made of Cu are sequentially deposited on asubstrate100 covered with an insulating film. A stacked layers film constituting theTMR element6 is deposited using sputtering. Here, it is desirable that theyoke2 is deposited under external magnetic field environment in order to arrange an easy magnetization axis in a direction of a long side of the writingwiring layer4.
• On the other hand, it is desirable that the magnetizationfree layer6bof theTMR element6 is deposited under external magnetic field environment such that the easy magnetization axis of the magnetizationfree layer6bis coincident with a direction substantially perpendicular to theyoke2, namely, a direction of a longitudinal axis of theTMR element6. Accordingly, when all the layers of theyoke2 to theupper electrode layer6eare deposited in bundle in the same apparatus, it is desirable that an apparatus which allows a direction of external magnetic field to rotate at least 900 is selected. In this embodiment, the magnetization fixing anneal is performed before this process starts in order to relax stress of the stacked layers film, but it may be performed after the process, or before and after the process.
• In theTMR element6 according to the embodiment, Ta serving as thelower electrode layer6a, Co—Fe—Ni serving as the magnetizationfree layer6b, Al₂O₃obtained by plasma-oxidizing Al serving as the tunnel barrier layer6c, Co—Fe serving as the magnetization pinned layer6d, Ir—Mn serving as the anti-ferromagnetic layer (not shown) for fixing magnetization of the magnetization pinned layer6d, and Ta serving as theupper electrode layer6eare sequentially stacked (refer toFIG. 5).
• Next, as shown inFIG. 6, the stacked layers of theupper electrode layer6eto theyoke2 are etched using lithography technique such that thewiring layer4 is formed in a predetermined shape. In the embodiment, an RIE (Reactive Ion Etching) apparatus where argon gas is mainly introduced is used for etching process, but an ion milling apparatus may be used instead thereof. An end face indicated withreference numeral7 inFIG. 6 is a long side of the wiring layer (wire)4 and corresponds to a short side of theTMR element6. TheTMR element6 is an element including the upper and lowerferromagnetic layers6band6dseparated from each other by an extremely thin tunnel barrier layer6c, where it is important for improvement in process yield that the upper layer and the lower layer are not short-circuited during etching process. The inventors have tried various etching work processes and have found that a main factor of short-circuiting is re-adhesion of material or metal which has been removed by the etching process to the vicinity of the tunnel barrier layer6c. In the embodiment, theyoke2 which is a lower layer is removed by etching, and thereafter metal which has been re-adhered to a side wall at a short side of theTMR element6 is removed while an insulating layer (not shown) which is a further lower layer is subsequently being etched, so that process yield is improved.
• As shown inFIG. 7, processing is conducted by performing etching for defining a long side edge of theTMR element6. A section shown inFIG. 7 is a section extending in a direction perpendicular to sections shown inFIGS. 5 and 6. Since an etching mask may define only a long side of theTMR element6 using photolithography, it is important to use a mask where a long side position of theTMR element6 is coincident with theTMR element6 and a short side position thereof exceeds theTMR element6. In this embodiment, a mask with a shape perpendicular to thewiring layer4, which is obtained by connecting long sides of a plurality ofTMR elements6 is used. Etching may be performed from theupper electrode layer6eto the magnetizationfree layer6b, but cutting-in may be conducted to such an extent that the resistivity of thewiring layer4 does not cause a problem about an electric circuit. In this embodiment, it is known that a short-circuiting failure rate on theTMR element6 increases according increase in an amount of cutting-in exceeding the magnetizationfree layer6b. Therefore, it is important for yield improvement to stop etching just after etching down to the magnetizationfree layer6bis completed.
• TheTMR element6 having the writingwiring layer4 is completed by the above process. Thereafter, as shown inFIG. 8, after an insulatingfilm10 with a thickness of 30 nm made of Al₂O₃is deposited by using sputtering, TEOS (tetra-etoxy-ortho-silicate) is plasma-decomposed to deposit an insulatingfilm12 with a thickness of 100 nm made of SiO₂to using a PECVD (plasma-enhanced chemical vapor deposition) process.
• Then, after material for planarization, such as planarizing resist is applied to obtain electric connection with theTMR element6, theupper electrode layer6eis exposed using a technique for a whole face etch back conducted by RIE, CMP (Chemical Mechanical Polishing) or the like (refer toFIG. 9). Of course, such a constitution may be employed that openings are formed in the insulatingfilm12 made of SiO₂and the insulatingfilm10 made of Al₂O₃so that theupper electrode6eis exposed.
• After an opening (not shown) for achieving electric connection with the MRAM driving circuit positioned further below is further formed, awiring layer14 with a three-layered structure of a Ti layer with a film thickness of 30 nm, an Al layer with a film thickness of 300 nm, and a Ti layer with a film thickness of 30 nm is deposited using sputtering process and thewiring layer14 is patterned in a predetermined shape using lithography technique to be completed (refer toFIG. 10). The wiring layer (wire)14 may be patterned in any direction, but it is desirable for further reducing a possibility of erroneous writing at a reading time that thewiring layer14 is patterned in parallel with a mask pattern for processing theTMR element6. Thereafter, an insulatinglayer18 made of SiN or the like is generally deposited on a required portion after thewire14 is patterned in order to improve reliability.
• FIG. 11 is a circuit diagram showing one specific example of an electric circuit of the magnetic memory according to the first embodiment of the present invention. The magnetic memory of the embodiment is provided with a plurality of memory cells, asense amplifier50, anddecoders52,54. Each memory cell has oneTMR element6, awriting wire4 corresponding to theTMR element6, and two transistors Tr1, Tr2 for writing selection corresponding to thewriting wire4. Memory cell selections at a writing-in time and at a reading-out time are conducted by thedecoder52 and thedecoder54. At the writing time, writing is performed by turning on two transistors Tr1, Tr2 in the selected memory cell by thedecoder54 and performing floating of thewire14 by thedecoder52 and thesense amplifier50. At the reading time, a resistance of the TMR element is read out by turning off the transistor Tr1 in the selected memory cell and turning on the transistor Tr2 therein by thedecoder54 to detect current flowing in thewire14, theTMR element6, and the transistor Tr2 by thesense amplifier50. Since thewire4 acts on only theTMR element6 corresponding thereto at the writing-in time, erroneous writing-in on theother TMR elements6 is principally prevented from occurring. In fact, no erroneous writing-in was found in the embodiment.
• Unless the structures of thewire4 andTMR elements6 deviate from the present invention, a design for a memory circuit can be modified freely regardless of the embodiment. For example, modification to a reading circuit with a higher reliability can be made by increasing the number of transistors to be used.
Second Embodiment
• Next, a constitution of a memory cell in a magnetic memory according to a second embodiment of the present invention is schematically shown inFIG. 12. The memory cell in the magnetic memory according to the embodiment is constituted such that, for example, a barrier metal layer3 with a film thickness of 10 nm made of Ta has been inserted between thewire4 connected to theTMR element6 constituting the memory cell and theyoke2 in the magnetic memory of the first embodiment. By inserting the barrier metal3, mutual diffusion between material constituting a composition element for thewire4, for example, Cu or Al, and material constituting theyoke2, for example, permalloy (Ni—Fe) can be prevented from occurring. As the barrier metal, any one of TaN, TiN and WN can be used besides Ta. A barrier metal layer may be provided between theyoke2 and abase substrate100.
• The magnetic memory of the embodiment can also reduce writing current without causing fluctuation of the writing characteristic like the first embodiment.
Third Embodiment
• Next, a constitution of a memory cell of a magnetic memory according to a third embodiment of the present invention is schematically shown inFIG. 13.
• In the first and second embodiments, writing is performed by turning on two transistors to cause current to flow in only in thewire4. At that time, magnetic field required for reversing magnetization of the magnetizationfree layer6bof theTMR element6 serves as a coercive force in a direction of an easy magnetization axis of theTMR element6.
• The third embodiment of the present invention has a constitution that anotherwire14 is formed on theTMR element6 so as to be perpendicular to the wire4 (refer toFIG. 13). In this embodiment, writing can be performed utilizing asteroid characteristic of theTMR element6 by causing current to flow in thewire4 and thewire14 simultaneously, and writing current is further reduced.
• Next, a method for manufacturing the magnetic memory according to the embodiment will be explained with reference toFIG. 14. The magnetic memory is manufactured like the magnetic memory of the first embodiment utilizing the steps shown in FIGS.5 to9 till exposure of theupper electrode layer6eof theTMR element6.
• Thereafter, after an opening (not shown) for achieving electric connection with the MRAM driving circuit positioned further below is formed, awiring layer14 with a three-layered structure of a Ti layer with a film thickness of 30 nm, an Al layer with a film thickness of 300 nm, and a Ti layer with a film thickness of 30 nm is deposited using sputtering process and thewiring layer14 is patterned so as to be perpendicular to the wiring layer (wire)4 using lithography technique to be completed (refer toFIG. 14). Thereafter, an insulating layer (not shown) made of SiN or the like is generally deposited on a required portion after thewire14 is patterned in order to improve reliability.
• FIG. 15 is a circuit diagram showing one specific example of an electric circuit of the magnetic memory according to the third embodiment of the present invention. The magnetic memory of the embodiment is provided with a plurality of memory cells, asense amplifier50, anddecoders52,54. Each memory cell is provided with oneTMR element6 and a selecting transistor Tr corresponding to theTMR element6, and each memory cell is connected to awire4 and awire14.
• At a writing time, writing is performed by causing current to flow into thewire4 and thewire14 simultaneously. At a reading time, reading is performed by turning on the selecting transistor Tr to cause current to flow in thewire14, theTMR element6, and the selecting transistor Tr and reading out a resistance value of theTMR element6. In this embodiment, a reversing magnetic field of the magnetization free layer in theTMR element6 is reduced to 70% of that in the first embodiment, so that writing current required for writing can be reduced as much as 30% even if currents flowing in thewire4 and thewire14 are summed.
• If the structures of thewire4 and theTMR structure6 and conducting writing using both thewire4 and thewire14 are implemented, a design for a memory circuit can be modified freely regardless of the embodiment. For example, modification to a reading circuit with a higher reliability can be made by increasing the number of transistors to be used, or erroneous writing may be prevented by attaching two selecting transistors to the writing wire like the first embodiment.
• As described above, according to this embodiment, writing current can be reduced without fluctuation of the writing characteristic.
Fourth Embodiment
• Next, a magnetic memory according to a fourth embodiment of the present invention will be explained with reference toFIG. 16 toFIG. 18.FIG. 16 is a perspective view schematically showing a constitution of a memory cell in the magnetic memory according to the embodiment. In the above third embodiment, thewire14 is formed of only a metal layer. In this embodiment, however, as shown inFIG. 16, such a structure is employed that ayoke16 made of a magnetic layer is stacked on thewiring layer14. In the embodiment, a barrier layer is not interposed between theyoke2 made of Ni—Fe and thewire4 made of Cu, or between theyoke2 and thebase substrate100, but barrier metal such as Ta, TaN, TiN, W, or WN may be interposed therebetween.
• Next, manufacturing steps in a method for manufacturing the magnetic memory according to the embodiment will be explained with reference toFIGS. 17 and 18. The magnetic memory obtained by the manufacturing method is manufactured like the magnetic memory of the first embodiment utilizing the steps shown in FIGS.5 to9 till exposure of theupper electrode layer6eof theTMR element6.
• Subsequently, after an opening for achieving electric connection with the MRAM driving circuit positioned further below is formed, awiring layer14 with a three-layered structure of a Ti layer with a film thickness of 30 nm, an Al layer with a film thickness of 300 nm, and a Ti layer with a film thickness of 30 nm is deposited using sputtering process and ayoke16 with a film thickness of 50 nm made of NiFe is patterned thereon using a sputtering process (refer toFIG. 17). Thereafter, thewiring layer14 and themagnetic layer16 are patterned using lithography technique such that a direction of an longitudinal axis of thewiring layer14 is perpendicular to a direction of a longitudinal axis of thewire4, so that thewire14 and theyoke16 formed thereon is completed. Of course, barrier metal of Ta, TaN, TiN, W, WN or the like may be disposed above, below or above and below theyoke16.
• An insulating layer made of SiN or the like is generally deposited on a required portion after the above wire is patterned in order to improve reliability.
• Writing and reading can be performed like the third embodiment. Since theyoke16 is provided so as to cover thewire14, the magnitude of the magnetic field generated from thewire14 becomes larger than that generated in the third embodiment. The shape of asteroid characteristic becomes more symmetrical than that in the third embodiment, so that erroneous writing could be reduced as much as 50%. As a result, this embodiment allowed 20% reduction of writing current as compared with the third embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
Fifth Embodiment
• Next, a magnetic memory according to a fifth embodiment of the present invention will be explained with reference toFIG. 19 toFIG. 21. FIGS.19 to21 are sectional views showing steps for manufacturing the magnetic memory according to the embodiment. The magnetic memory of the fourth embodiment employs such a constitution that only an upper face of thewire14 is covered with theyoke16, but the magnetic memory of this embodiment is constituted such that not only an top face of thewire14 but also side faces thereof are provided with a magnetic layer (yoke)20.
• First, the magnetic memory of the embodiment is manufactured like the magnetic memory of the first embodiment utilizing the steps shown in FIGS.5 to9 till exposure of theupper electrode layer6eof theTMR element6. Subsequently, after an opening for achieving electric connection with the MRAM driving circuit positioned further below is formed, awiring layer14 with a three-layered structure of a Ti layer with a film thickness of 30 nm, an Al layer with a film thickness of 300 nm, and a Ti layer with a film thickness of 30 nm is deposited using sputtering process, and ayoke16 with a thickness of 50 nm made of NiFe is patterned thereon using a sputtering process. Thereafter, thewiring layer14 and themagnetic layer16 are patterned using lithography technique such that a direction of an longitudinal axis of thewiring layer14 is perpendicular to a direction of a longitudinal axis of thewire4, so that thewire14 and theyoke16 formed thereon is completed (refer toFIG. 19).
• Then, amagnetic layer20 with a film thickness of 60 nm made of NiFe is further deposited on the whole surface using sputtering process (refer toFIG. 20). Of course, barrier metal of Ta, TaN, TiN, W, WN, or the like is disposed above or below themagnetic layer20. Subsequently, the magnetic layer (yoke)20 is left only on side faces of thewiring layer14 and theyoke16 by performing etch back on the whole face of themagnetic layer20 until the insulatinglayer12 is exposed (refer toFIG. 21). In this embodiment, an RIE apparatus in which argon gas is mainly introduced is used for performing the etch back, but an ion milling apparatus may also be used therefor.
• An insulating layer made of SiN or the like is generally deposited on a required portion after the above wire is patterned in order to improve reliability.
• Writing and reading can be performed like the third embodiment. In this embodiment, since such a constitution is employed that the top face of thewire14 is covered with theyoke16 and the side faces thereof are surrounded by theyoke20, magnetic field can be applied to theTMR element6 more effectively. The asteroid characteristic became substantially completely symmetrical so that erroneous writing could be reduced. As a result, in the embodiment, writing current could be reduced 20% from that in the fourth embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
Sixth Embodiment
• Next, a magnetic memory according to a sixth embodiment of the present invention will be explained with reference toFIG. 22 toFIG. 26. FIGS.22 to26 are sectional views showing steps for manufacturing the magnetic memory according to the embodiment. The magnetic memory of the fifth embodiment employs such a constitution that theyoke16 is formed on the top face of thewire14 and theyoke20 is formed on the side faces thereof. In this embodiment, however theyoke20 on the side faces of thewire14 is formed so as to extend to a position of the magnetization free layer in theTMR element6.
• First, the magnetic memory of the embodiment is manufactured like the magnetic memory of the first embodiment utilizing the steps shown in FIGS.5 to9 till exposure of theupper electrode layer6eof theTMR element6. Subsequently, after an opening for achieving electric connection with the MRAM driving circuit positioned further below is formed, awiring layer14 with a three-layered structure of a Ti layer with a film thickness of 30 nm, an Al layer with a film thickness of 300 nm, and a Ti layer with a film thickness of 30 nm is deposited using sputtering process, and ayoke16 with a film thickness of 50 nm made of NiFe is patterned thereon using a sputtering process (refer toFIG. 22). Thereafter, thewiring layer14 and themagnetic layer16 are patterned using lithography technique such that a direction of a longitudinal axis of thewiring layer14 is perpendicular to a direction of a longitudinal axis of thewire4, so that thewire14 and theyoke16 formed thereon is completed (refer toFIG. 23). Of course, barrier metal of Ta, TaN, TiN, W, WN or the like may be disposed above, below or above and below theyoke16.
• The insulatingfilm12 made of SiO₂is selectively etched in an RIE apparatus using etching gas which mainly includes CF₄, so that the insulatingfilm10 made of Al₂O₃is exposed (refer toFIG. 24). In this embodiment, the film thickness of the insulatingfilm10 made of Al₂O₃is set to 30 nm, and it is the same as thickness from thewire4 to the magnetization free layer of theTMR element6. Accordingly, the film thickness of the insulatingfilm10 made of Al₂O₃should vary so as to correspond to the constitution of theTMR element6.
• Thereafter, amagnetic layer20 with a film thickness of 60 nm made of NiFe is further deposited on the whole surface using sputtering process (refer toFIG. 25). Of course, barrier metal of Ta, TaN, TiN, W, WN, or the like is disposed above, below or above and below themagnetic layer20. Then, the magnetic layer (yoke)20 is left only on side faces of theinsulting layer12, thewiring layer14, and theyoke16 by performing etch back on themagnetic layer20 until the insulatinglayer10 made of Al₂O₃is exposed. In this embodiment, an RIE apparatus in which argon gas is mainly introduced is used for performing the etch back, but an ion milling apparatus may also be used therefor. In the RIE using argon gas mainly, since a selective ratio of NiFe constituting theyoke20 and the Al₂O₃constituting the insulatingfilm10 can be taken to be about 20, such a drawback that the insulatinglayer10 made of Al₂O₃is cut in to expose thewire4 can be prevented. It is known that, when etching is performed using argon gas, material or metal removed by the etching is re-adhered to themagnetic layer20 on the side wall of thewire14 to lower the efficiency of the induced magnetic field generated from thewire14. In this embodiment, it is possible to remove the material or metal re-adhered to themagnetic layer10 on the side wall of thewire14 while the insulatinglayer10 made of Al₂O₃is being etched after themagnetic layer20 on the top face of themagnetic layer16 is etched.
• An insulating layer made of SiN or the like is generally deposited on a required portion after the above wire is patterned in order to improve reliability.
• Writing and reading operations can be performed like the third embodiment. Since themagnetic layer20 extends downwardly to the side face of the magnetizable in theTMR element6, magnetic field can be caused to act on theTMR element6 more effectively. As a result, in this embodiment, writing current could be reduced 20% as compared with the fifth embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
Seventh Embodiment
• Next, a magnetic memory according to a seventh embodiment of the present invention will be explained with reference toFIG. 27 toFIG. 33.FIG. 27 is a perspective view schematically showing a memory cell in a magnetic memory according to this embodiment, and FIGS.28 to33 are sectional views showing manufacturing steps of a magnetic memory according to the embodiment. The magnetic memory of the embodiment is constituted such that an arranging relationship between theTMR element6 and thewiring layer4 is reversed upside down.
• Next, a method for manufacturing a magnetic memory according to the embodiment will be explained.
• As shown inFIG. 28, first, a stacked layers film constituting theTMR element6 is deposited on asubstrate100 including a lower layer where a driving circuit for a memory section and the like have been fabricated. In the embodiment, the stacked layers in theTMR element6 are prepared by sequentially stacking Ta serving as a lower electrode layer, Co—Fe—Ni serving as magnetizable, Al₂O₃obtained by plasma-oxidizing Al and serving as a tunnel barrier layer, Co—Fe serving as the magnetization pinned layer, Ir—Mn serving as an anti-ferromagnetic layer, and Ta serving as an upper electrode layer.
• Next, processing is conducted by performing etching for defining a long side edge of the TMR element6 (refer toFIG. 29). Since an etching mask may define only a long side of theTMR element6 using photolithography, a mask with a shape perpendicular to thewiring layer4 obtained by connecting long sides of a plurality ofTMR elements6 is used.
• Next, TEOS is plasma-decomposed to deposit an insulatingfilm22 with a thickness of 100 nm made of SiO₂using a PECVD process (refer toFIG. 30), and after planarization resist is applied on the insulatingfilm22, etch back is performed on the insulatingfilm22 to expose an upper electrode layer in the TMR element6 (refer toFIG. 31).
• Thereafter, after an opening (not shown) for achieving electric connection with the MRAM driving circuit positioned further below is formed in the insulatingfilm22, awiring layer4 with a film thickness of 20 nm made of Cu and amagnetic layer2 with a film thickness of 10 nm made of Ni—Fe are sequentially deposited on the insulatinglayer22 so as to fill in the opening (refer toFIG. 32). In the embodiment, barrier metal is neither disposed above, below, nor above and below themagnetic layer2 made of Ni—Fe, but barrier metal of Ta, TaN, TiN, W, WN, or the like may be disposed, of course.
• Etching process is applied to the stacked layers of themagnetic layer2 to the lower electrode layer in theTMR layer6 such that thewiring layer4 is formed in a predetermined shape (refer toFIG. 33). Since an etching mask used at that time may define only a short side of theTMR element6 and thewiring layer4 using photography, a mask with a shape obtained by connecting short sides of a plurality of TMR elements may be used as the etching mask. The length of thewiring layer4 in its longitudinal direction or the like is determined by the etching process. FIGS.28 to32 are sectional views taken along a plane extending along a short side direction of theTMR element6, andFIG. 33 is a sectional view taken along a plane extending along a longitudinal side direction of theTMR element6. That is,FIG. 33 shows a section perpendicular to sections shown in FIGS.28 to32.
• In the embodiment, an RIE apparatus in which argon gas is mainly introduced is used for performing the etch back, but an ion milling apparatus may also be used therefor. TheTMR element6 is an element including the upper and lower layers separated from each other by an extremely thin tunnel barrier layer, where it is important for improvement in process yield that the upper layer and the lower layer are not short-circuited during etching process. The inventors have tried various etching work processes and have found that a main factor of short-circuiting is re-adhesion of material or metal which has been removed by etching process to the vicinity of the tunnel barrier layer. In the embodiment, the lower electrode layer which is a lower layer is removed by etching, and thereafter metal which has been re-adhered to a side wall at a short side of theTMR element6 is removed while an insulating layer (not shown) which is a lower layer is subsequently being etched, so that the process yield is improved.
• TheTMR element6 having thewriting wire4 is completed in this manner. In the seventh embodiment, a circuit electrically equivalent to that in the first embodiment is manufactured. Since it is unnecessary to form a wire for connection with the lower electrode in theTMR element6 in the seventh embodiment, the number of steps is reduced, so that manufacturing can be performed inexpensively in mass production.
• An insulating layer made of SiN or the like is generally deposited on a required portion after the above wire is processed in order to improve reliability. Writing-in and reading-out operations are performed like the first embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
Eighth Embodiment
• Next, a magnetic memory according to an eighth embodiment of the present invention will be explained with reference toFIG. 34 toFIG. 39. FIGS.34 to39 are sectional views showing steps for manufacturing the magnetic memory according to the embodiment. The magnetic memory of the embodiment employs such a constitution that awriting wire14 is further provided below theTMR element6 in the seventh embodiment.
• Awriting wire14 is formed on asubstrate100 including a lower layer where a driving circuit for a memory section and the like have been fabricated so as to be perpendicular to awire4 described later (refer toFIG. 34). In the embodiment, thewire14 is formed utilizing damascene process using Cu. Respective steps performed in the damascene process are well-known, and explanation thereof will be omitted here. Of course, a process where, after awire14 is formed of Al and embedding with an insulating film of SiOx or the like is performed, thewire14 is exposed by planatization may be employed. In the embodiment,barrier metal13 is provided between thesubstrate100 and the wire14 (refer toFIG. 34). Then, a stacked layers film constituting aTMR element6 is deposited (refer toFIG. 35). In the embodiment, stacked layers constituting theTMR element6 are formed by defining a lower layer side as a magnetization free layer, and stacking Ta serving as a lower electrode layer, Co—Fe—Ni serving as a magnetization free layer, Al₂O₃obtained by plasma-oxidizing Al and serving as a tunnel barrier layer, Co—Fe serving as a magnetization pinned layer, Ir—Mn serving as an anti-ferromagnetic layer, and Ta serving as an upper electrode (not shown).
• Next, processing is conducted by performing etching for defining a long side edge of the TMR element6 (refer toFIG. 35). Since an etching mask may define only a long side of theTMR element6 using photolithography, a mask having a shape which is perpendicular to thewiring layer4 described later and which is obtained by connecting long sides of a plurality of TMR elements is used.
• Next, TEOS is plasma-decomposed to deposit an insulatingfilm24 with a thickness of 100 nm made of SiO₂using a PECVD process (refer toFIG. 36). Subsequently, after material for planarization such as planarization resist is applied on the insulatingfilm24, an upper electrode layer in theTMR element6 is exposed using a whole face etch back process such as RIE or CMP (refer toFIG. 37).
• Next, after an opening (not shown) for achieving electric connection with the MRAM driving circuit positioned further below is formed in the insulatingfilm24, awiring layer4 with a film thickness of 20 nm made of Cu and amagnetic layer2 with a film thickness of 10 nm made of Ni—Fe are sequentially deposited on the whole surface of the insulatinglayer24 so as to fill in the opening (refer toFIG. 38). In the embodiment, barrier metal is not disposed above, below, or above and below themagnetic layer2 made of Ni—Fe, but barrier metal of Ta, TaN, TiN, W, WN, or the like may be disposed, of course.
• Next, etching process is applied to the stacked layers of themagnetic layer2 to the lower electrode layer in theTMR layer6 such that thewiring layer4 is formed in a predetermined shape (refer toFIG. 39). Since an etching mask used at that time may define only a short side of theTMR element6 and thewiring layer4 using photography, a mask with a shape obtained by connecting short sides of a plurality of TMR elements may be used as the etching mask. The length of thewiring layer4 in its longitudinal direction or the like is determined by the etching process. FIGS.34 to38 are sectional views taken along a plane extending along a short side direction of theTMR element6, andFIG. 39 is a sectional view taken along a plane extending along a longitudinal side direction of theTMR element6. That is,FIG. 39 is a section perpendicular to sections shown in FIGS.34 to38. In the embodiment, an RIE apparatus in which argon gas is mainly introduced is used for performing the etch back, but an ion milling apparatus may also be used therefor.
• TheTMR element6 having thewriting wire4 is completed in this manner. An insulating layer (not shown) made of SiN or the like is generally deposited on a required portion after the above wire is processed in order to improve reliability. Writing and reading operations are performed like the third embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
Ninth Embodiment
• Next, a magnetic memory according to a ninth embodiment of the present invention will be explained with reference toFIG. 40 toFIG. 49. FIGS.40 to49 are sectional views showing steps for manufacturing the magnetic memory according to the embodiment. The magnetic memory of the embodiment employs such a constitution that amagnetic layer16 is provided below awiring layer14 in the magnetic memory in the eighth embodiment.
• Amagnetic layer16 with a film thickness of 50 nm made of NiFe, and awiring layer14 with a three-layered structure of a Ti layer with a film thickness of 30 nm, an Al layer with a film thickness of 30 nm, and a Ti layer with a film thickness of 30 nm are sequentially deposited on asubstrate100 including a lower layer where a driving circuit for a memory section and the like have been fabricated (refer toFIG. 40). Subsequently, themagnetic layer16 and thewiring layer14 are patterned so as to be perpendicular to awiring layer4 described later by using an RIE apparatus (refer toFIG. 41).
• Thereafter, TEOS is plasma-decomposed to deposit an insulatingfilm26 with a thickness of 100 nm made of SiO₂using a PECVD process (refer toFIG. 42). Further, after material for planarization such as planarization resist is applied on the insulatingfilm26, a whole surface etch back is performed utilizing a combination of RIE and CMP to expose a surface of the wiring layer14 (refer toFIG. 43).
• Then, astacked layers film6 constituting a TMR element is deposited on a whole surface of the insulating film26 (refer toFIG. 44). In the embodiment, stacked layers constituting theTMR element6 are formed by defining a lower layer side as a magnetization free layer, and stacking Ta serving as a lower electrode layer, Co—Fe—Ni serving as a magnetization free layer, Al₂O₃obtained by plasma-oxidizing Al and serving as a tunnel barrier layer, Co—Fe serving as a magnetization pinned layer, Ir—Mn serving as an anti-ferromagnetic layer, and Ta serving as an upper electrode.
• Next, processing is conducted on thestacked layers film6 by performing etching for defining a long side edge of the TMR element6 (refer toFIG. 45). Since an etching mask may define only a long side of theTMR element6 using photolithography, a mask having a shape which is perpendicular to thewiring layer4 described later and which is obtained by connecting long sides of a plurality of TMR elements, is used.
• Next, TEOS is plasma-decomposed to deposit an insulatingfilm28 with a thickness of 100 nm made of SiO₂using a PECVD process (refer toFIG. 46). Subsequently, after material for planarization such as planarization resist is applied on the insulatingfilm28, etch back is applied to the insulatingfilm28 to expose an upper electrode layer in theTMR element6 using an etch back process such as RIE or CMP (refer toFIG. 47).
• After an opening (not shown) for achieving electric connection with the MRAM driving circuit positioned further below is formed in the insulatingfilm28, awiring layer4 with a film thickness of 20 nm made of Cu and amagnetic layer2 with a film thickness of 10 nm made of Ni—Fe are sequentially deposited on the insulatinglayer28 so as to fill in the opening (refer toFIG. 48). In the embodiment, barrier metal is neither disposed above, below, nor above and below themagnetic layer2 made of Ni—Fe, but barrier metal of Ta, TaN, TiN, W, WN, or the like may be disposed, of course.
• Next, etching process is applied to the stacked layers of themagnetic layer2 to the lower electrode layer in theTMR layer6 such that thewiring layer4 is formed in a predetermined shape (refer toFIG. 49). Since an etching mask may define only a short side of the TMR element and thewiring layer4 using photography, a mask with a wiring shape obtained by connecting short sides of a plurality of TMR elements may be used as the etching mask. The length of thewiring layer4 in its longitudinal direction or the like is determined by the etching process. FIGS.40 to48 are sectional views taken along a plane extending along a short side direction of theTMR element6, andFIG. 49 is a sectional view taken along a plane extending along a longitudinal side direction of theTMR element6. That is,FIG. 49 is a section perpendicular to sections shown in FIGS.40 to48.
• An insulating layer made of SiN or the like is generally deposited on a required portion after the above wire is processed in order to improve reliability. Writing and reading operations are performed like the third embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
Tenth Embodiment
• Next, a magnetic memory according to a tenth embodiment of the present invention will be explained with reference toFIG. 50.FIG. 50 is a sectional view schematically showing a constitution of a memory cell in a magnetic memory according to the embodiment. The magnetic memory of the embodiment employs such a structure that amagnetic layer16 is formed on not only a lower face of awiring layer14 but also a side face thereof in the magnetic memory according to the ninth embodiment.
• A method for manufacturing the magnetic memory of the embodiment will be explained. Amagnetic layer16 with a three-layered structure of a TaN film16awith a film thickness of 30 nm, a NiFe film16bwith a film thickness of 60 nm, and aTiN film16cwith a film thickness of 30 nm is formed, using sputtering process, on a surface of a groove in asubstrate100 including a lower layer where a driving circuit for a memory section and the like have been fabricated, and thereafter awiring layer14 made of Cu is formed using damascene process so as to fill in the groove (refer toFIG. 50). Respective steps in the damascene process are well-known and explanation thereof is omitted.
• Astacked layers film6 constituting a TMR element is deposited on thewiring layer14. Steps subsequent thereto are performed like the ninth embodiment, where an insulatingfilm28 is provided on a side face of the TMR element, awiring layer4 is formed so as to electrically connect to the upper electrode in theTMR element6, and amagnetic layer2 serving as a yoke is formed on the wiring layer4 (refer toFIG. 50). Writing and reading operations are performed like the third embodiment.
• As explained above, according to this embodiment, writing current can be reduced without fluctuation in writing characteristic.
• For constituting a MRAM with a mass storage, for example, a 32 Mbit class, it is necessary reduce a ratio of an area occupied by a peripheral circuit to increase an occupation ratio of a memory array. Therefore, it is necessary to set an array block size per unit to a 1 Mbit array. However, since a writing current value is as large as several mA to 10 mA at present, a voltage in the order of 2V is generated at both ends of a writing wire resistor, which not only makes it impossible to achieve voltage reduction down to the order of 1V but also makes it difficult to raise a writing current waveform at a high speed. Thus, a high speed memory or storage can not be realized.
• In order to achieve mass storage (higher integration), when a width of a tunnel junction element (hereinafter, also called MTJ (Magnetic Tunneling Junction) which is a storage element included in each cell in MRAM is reduced to be fine, thermal agitation resistance is remarkably reduced, which results in difficulty in securing non-volatile.
• Further, in a system where writing current is caused to flow in both a bit line and a word line and writing is performed at an MTJ cell positioned at a crossing point of the bit line and the word line, erroneous writing may occur at an MTJ cell positioned at another point other than the crossing point and excited to a semi-selected state or it may be difficult to secure non-volatile of the excited MTJ cell. That is, since a margin for writing is reduced, erroneous writing may occur or it may be difficult to secure non-volatile.
• A reversing magnetic field Hsw required for rewriting magnetization information in a recording layer constituting an MTJ is schematically expressed as follows:
  Hsw˜4πMs×t/F(Oe)  (1)
• In this connection, a magnetic anisotropic energy density Ku is schematically expressed as follows:
  Ku=Hsw·Ms/2  (2)
• Here, Ms represents saturated magnetization of a recording layer, t represents a thickness of the recording layer and F represents a width of the recording layer.
• On the other hand, when the volume of the recording layer is represented as V, the thermal agitation resistance of the recording layer is represented as magnetic energy Ku×V. Accordingly, in an MTJ where an aspect ratio (length/width) of a recording layer is 2, the thermal agitation resistance is as follows:$\begin{array}{c}Ku\times V=\left(Hsw·Ms/2\right)\times V\\ =\left(4\pi Ms\times t/F\right)\times \left(Ms/2\right)\times F\times 2F\times t\\ =4\pi M{s}^2\times {\mathrm{<figure-callout\; label="t"\; filenames="US20050141148A1-20050630-D00001.png,US20050141148A1-20050630-D00003.png"\; state="\{\{state\}\}">t</figure-callout>}}^2\times F\\ =Hs{\mathrm{<figure-callout\; label="w"\; filenames="US20050141148A1-20050630-D00001.png,US20050141148A1-20050630-D00003.png"\; state="\{\{state\}\}">w</figure-callout>}}^2\times F^3/\left(4\pi \right)\end{array}$
• Accordingly, when the MTJ is made fine, namely, the width of the recording layer is made small, it is necessary to enlarge the reversing magnetic field Hsw in order to secure the thermal agitation resistance.
• Since writing current of about 8 mA is required in a recording layer with a width of about 0.4 μm, the writing current further increases according to progress of fineness. It is necessary to reduce the writing current value to about 1.5 mA or less in order to perform writing at a high speed of about 10 nsec for mass storage, and it is preferable for reducing a peripheral circuit in size that the writing current value is set to about 0.5 mA.
Eleventh Embodiment
• A magnetic memory (hereinafter, also called MRAM (MagnetoResistive Random Access Memory) will be explained with reference toFIG. 51A. The magnetic memory according to the embodiment is provided with a plurality of memory cells.FIG. 51A is a sectional view showing a constitution of a memory cell in the magnetic memory of the embodiment. Each memory cell is provided with a tunnel junction element102 (hereinafter, also called MTJ (magnetic tunneling junction). TheMTJ102 is provided with amagnetic recording layer104 whose direction of magnetization varies according to external magnetic field, atunnel barrier layer106, a magnetization pinnedlayer108 whose direction of magnetization is pinned, and ananti-ferromagnetic layer110 which pines the direction of magnetization of the magnetization pinnedlayer108. Themagnetic recording layer104 in theMTJ102 is provided on awriting wire120. Thewriting wire120 is provided on ayoke125 made of soft magnetic material which increases magnetic flux generated by current flowing in thewriting wire120.
• That is, in the embodiment, a structure where theyoke125, thewriting wire120, themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer8, and theanti-ferromagnetic layer110 are stacked is employed. Such a constitution is employed in the embodiment that end faces of thewriting wire120 and the yoke125 (left and right end faces onFIG. 51A), and end faces of themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer108, and the anti-ferromagnetic layer110 (left and right end faces onFIG. 51A) are positioned on the same plane. That is, theyoke125, thewriting wire120, themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer108, and theanti-ferromagnetic layer110 have the same width W. Incidentally, in the embodiment, theyoke125, thewriting wire120, themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer108, and theanti-ferromagnetic layer110 are stacked in this order, but a structure the stacking order is reversed may be employed.
• In the embodiment, material for theyoke125 is selected so as to obtain theyoke125 whose relative magnetic permeability is about 100 and whose direction of magnetization is generally parallel to or anti-parallel to writing current is selected. In the embodiment, the direction of magnetization of themagnetic recording layer104 is generally perpendicular to writing current flowing in thewriting wire120.
• In the embodiment, writing data in a memory cell is performed by causing writing current to flow in thewriting wire125 and a writing bit line (not shown) generally perpendicular to thewriting wire125 and reversing magnetization of themagnetic recording layer104 in the MTJ with magnetic field generated by the current. Reading data from a memory cell is performed by applying a voltage between a reading-out wire (not shown) electrically connecting to theanti-ferromagnetic layer110 and thewriting wire120 to measure current flowing in theMTJ102 or by causing a constant current to flow between the reading-out wire and the writing wire to measure a voltage between the reading-out wire and thewriting wire120.
• Though it is generally said that a current-magnetic field converting efficiency is made double and a writing current value is reduced to half by forming a yoke in a writing wire, this will be a limitation in such yoke formation. It is expected that a current value obtained when a yoke is formed in a writing wire and the width W of a MTJ is 240 nm is about 6 mA.
• The magnitude of writing current in the embodiment will be explained below. As described above, in the embodiment, such a constitution is employed that the end faces of theyoke125 and thewriting wire120 and the end face of theMTJ102 are positioned on the same plane. When the film thickness sizes of themagnetic recording layer104, thewriting wire102, and theyoke125 are represented as T₁, T₂, and T₃, and the relative magnetic permeabilities of themagnetic recording layer104, thewriting wire102, and theyoke125 are represented as μ₁, β₂(=1), and μ₃, an effective length Leff of a magnetic path of a magneticclosed circuit130 shown with a broken line inFIG. 51A is expressed as follows:
• Leff=2×T₂+W/μ₁+W/μ₃
• Here, under conditions of W=240 nm, T₂=20 nm, μ₁=5, and μ₃=100, since the magnetic path length (W/μ₃) on the side of the yoke can be substantially disregarded, the effective magnetic length Leff of the magneticclosed circuit130 will be 88 nm or so in this embodiment.
• On the other hand, in an ordinary writing wire with a yoke, since end faces of the yoke and writing wire, and an end face of an MTJ are not positioned on the same plane, which is different from the embodiment, it is necessary to provide a margin of 50 nm for allowing an alignment error on both side faces. Further, since the writing wire and a magnetic recording layer of the MTJ are separated from each other in a distance of 50 nm or more by an insulating layer or the like, the effective magnetic path length will be 360 nm or more.
• On the other hand, in the embodiment, since it is unnecessary to provide an alignment margin, and the magnetic path length can be disregarded, the effective magnetic path length Leff of the magneticclosed circuit130 will be 88 nm or so. When identical writing currents are caused to flow in the memory cell in the embodiment and the ordinary writing wire with a yoke, respectively, magnetic fields generated in the respective memory cells are in inversely proportional to the magnetic path length.
• Therefore, the magnitude of the magnetic field generated in the memory cell in the embodiment becomes 4.09 (=360/88) times the magnitude of the magnetic field generated in the memory cell having the ordinary writing wire with a yoke. That is, this means increase the current-magnetic field conversion efficiency up to 4.09 times. Further, this increase means that the writing current value can be reduced to 1/4.09=0.24. As a result, the writing current value in the memory cell of the embodiment can be reduced from 6 mA to 1.5 mA, as compared with the memory cell having the ordinary writing wire with a yoke.
• Furthermore, when the film thickness T₂of thewriting wire106 is 10 nm, the effective magnetic path length Leff becomes W/5+2×T2≈68 nm and it can be reduced. As compared with the memory cell having the ordinary writing wire with a yoke, the current-magnetic field conversion efficiency is increased up to 360/68 times so that the writing current value can be reduced to 68/360=0.19 times. That is, the writing current value is reduced to 1.1 mA.
• In addition, when the relative magnetic permeability of themagnetic recording layer104 in theMTJ102 is 10, the effective magnetic path length can be reduced to about W/10+2×T2˜44 nm, so that the writing current value becomes 0.73 mA. This value is very close to a target value of 0.5 mA of a writing current desirable for reducing a peripheral circuit of a magnetic memory.
• A memory cell according to the embodiment was actually made on an experimental base so as to meet W=240 nm, T₂=10 nm, μ₁=10, and μ₃=100 and was verified. The writing current value was about 1 mA. The value was very close to the target value (1 mA) desirable for realizing high speed writing of about 10 nsec or so.
• Experiment about non-volatile of the memory cell made on an experimental base was made. The non-volatile was larger than one expected. It is estimated that this is because, even if magnetizations of themagnetic recording layer104 in theMTJ102 and thestacked yoke125 are perpendicular to each other, they are coupled to each other. As a result, it was found that the thermal agitation resistance in this embodiment was remarkably improved as compared with the conventional MRAM. This was a completely unknown matter, which was first clarified in this experiment.
• Considering the improvement of the thermal agitation resistance, it was found that the non-volatile could be secured, even if the reversing magnetic field of themagnetic recording layer104 in theMTJ102 was reduced to ⅕. As a result, the writing current value of the memory cell according to the embodiment was about ⅕ of 0.73 mA which is the writing current value calculated regarding the effective magnetic path length of about 44 nm, namely, 0.14 mA. Accordingly, significant reduction was achieved from the writing current of 6 mA in the memory cell having the ordinary writing wire with a yoke to 0.14 mA. 0.5 mA or less which was the target value desired for reducing the peripheral circuit for the magnetic memory in size could be achieved.
• As the result of serious analysis on the above, it was found that such an effect or advantage that the writing current could be largely reduced was not inherent to the stacked yoke but was realized by setting the magnetization direction of theyoke125 to the writing current to be generally parallel or anti-parallel (the relative magnetic permeability of theyoke125 was a value of 100 or so) to each other and setting the relative magnetic permeability of hemagnetic recording layer104 in theMTJ102 to 5 or more.
• In the memory cell according to the embodiment, average generation magnetic field Heff (Oe) generated in the magneticclosed circuit130 shown inFIG. 51A when three kinds of memory cells having the relative magnetic permeability μ₃of themagnetic recording layer104 in theMTJ102 of 1, 5, and 10 were prepared and the relative magnetic permeability μ₃of theyoke125 was changed to the respective memory cells is shown inFIG. 52.FIG. 52 is a characteristic diagram where a graph g₁shows a case that the relative magnetic permeability μ₁of themagnetic recording layer4 is 10, agraph92 shows a case that the relative magnetic permeability μ₁of themagnetic recording layer4 is 5, and a graph93 shows a case that the relative magnetic permeability μ₁of themagnetic recording layer4 is 1.
• As understood from the characteristic diagram, the average generation magnetic field Heff is approximately constant, when the relative magnetic permeability3 takes a value in the vicinity of 100, for example, μ₃is in a range of 80 to 120. In that case, if the relative magnetic permeability of themagnetic recording layer104 is 5 or more, the average generation magnetic field Heff becomes 35 Oe or more.
• It is generally preferable for maintaining non-volatile of themagnetic recording layer104 that the average generation magnetic field Heff is 30 Oe or more. As understood fromFIG. 52, when the relative magnetic permeability μ₁of themagnetic recording layer104 is 5 or more and the relative magnetic permeability μ₃of theyoke125 is 30 or more, the average generation magnetic field Heff becomes 30 Oe or more, so that the non-volatile of themagnetic recording layer104 can be maintained.
• As explained above, according to the embodiment, since writing current can be reduced, high speed writing can be realized, and since the thermal agitation resistance is high, even if fineness is performed, the non-volatile can be secured. Thereby, mass storage and high speed writing can be achieved in this embodiment.
Twelfth Embodiment
• Next, a magnetic memory according to a twelfth embodiment will be explained. The magnetic memory of the first embodiment has a constitution that electro-migration resistance of thewriting wire120 has been improved in the magnetic memory according to the eleventh embodiment.
• In the magnetic memory, the electro-migration of thewriting wire120 is a pending matter. When the width of thewriting wire120 is set to 240 nm and the thickness thereof is set to 20 nm for the writing current of 1 mA, the current density is 2×10⁷A/cm². The value is as large as 4 to 10 times of the allowable value applied when Cu is used for the material for thewriting wire120. Even if the writing current value can be set to 0.14 mA, the current density becomes 3×10⁷A/cm², which does not solve the above pending problem. In research through an experiment, it was found that there was a case that electro-migration did not occur even at a current density of 2×10⁷A/cm², which was different from the inventor's estimation. It was found that this phenomenon was specific to a case that, when thewriting wire120 made of Cu was thinned to about 30 nm or less, yoke material (NiFe, CoFe, CoZrNb) which was material with a high melting point was used in theyoke125 serving as the base for thewriting wire120, a case that ametal layer123 of Ta, Ti, or the like was disposed in an interface between thewriting wire120 and theyoke125, as shown inFIG. 51B, and a case that an MTJ layer was directly disposed on an upper face of thewriting wire120 made of Cu.
• In the embodiment, therefore, electro-migration can be prevented from occurring by thinning the film thickness of thewriting wire120 to 30 nm or less and using material with a high melting point as the material for theyoke125. In this case, as shown inFIG. 51B, it is preferable that ametal layer123 of Ta, Ti, or the like is provided in an interface between thewriting wire120 and theyoke125.
• This embodiment also allows mass storage and high speed writing like the eleventh embodiment.
Thirteenth Embodiment
• Next, a magnetic memory according to a thirteenth embodiment of the present invention will be explained. The magnetic memory of the embodiment has a constitution that a writing selecting transistor is disposed for each memory cell in the eleventh or twelfth embodiment. The writing selecting transistor is electrically connected at one of its source and drain to thewriting wire120, and it serves as a word line for selection of a memory cell performed by a gate.
• By providing a writing selecting transistor for each memory cell like this embodiment, a non-selected memory cell is prevented from being put in a semi-selected state. Therefore, the reversing magnetic field can be reduced to ½ or less of the reversing magnetic field where the improvement of the thermal agitation resistance is taken in consideration. Thereby, the writing current value can be reduced to ½ of the writing current of 0.14 mA where the improvement of the thermal agitation resistance is taken in consideration, namely, 0.1 mA or so. An erroneous action in writing is prevented and a very board margin for a writing circuit design can be secured.
• This embodiment also allows mass storage and high speed writing like the eleventh embodiment.
• By combining all the constitutions of the eleventh to thirteenth embodiments, a margin for the writing circuit could be enlarged, the peripheral circuit could be simplified and reduced in size, and the occupation ratio of the memory array could be reduced to 65% equivalent to that in an ordinary memory. Even if the width of the MTJ was further made fine to 100 nm or so, the writing current value could be reduced to 0.5 mA, and even if a writing transistor was added, the cell area could be reduced to 0.5 μm²or less. Thereby, a high speed and mass storage MRAM exceeding 64 Mbits can be provided.
• It was found that a memory cell in which a writing current value was slightly high occurred in the MRAM made on a trial base. The result estimated from an experiment about a magnetization course of a magnetic recording layer of the memory cell is shown inFIG. 53. It was found that magnetization of an excellent memory cell in which a writing current value was low increased monotonously to any applied magnetic field H (refer to graph g₁), but a poor memory cell included a region where magnetization M of its magnetic recording layer did not react to a writing current to stagnate (refer to graph g₂).
• It was found that it was effective for avoiding the stagnation of the magnetization M of the magnetic recording layer to the applied magnetic field H that the direction of magnetization (the easy magnetization axis)105 of themagnetic recording layer104 in the MTJ was not perpendicular to the applied magnetic field H but it was inclined thereto. Specifically, as shown inFIG. 55, it will be effective to employ such an arrangement that a long side direction (the easy magnetization axis105) of themagnetic recording layer104 is not perpendicular to the a direction of a writing current flowing in the writing wire120 (that is, a direction in which thewriting wire120 extends) but it is inclined thereto. It is preferable that the inclined angle θ is about 45°.FIG. 55 is a plan view of themagnetic recording layer104 and thewriting wire120.
• Similar advantage or merit could be achieved even if theMTJ102 was formed in an almost cross shape, as shown inFIG. 56A, or even if themagnetic recording layer104 was formed in an asymmetrical shape (for example, an S shape or an inverse S shape having projections at both ends) to an axis of the writing wire in its widthwise direction, as shown inFIG. 56B. As shown inFIGS. 56C and 56D, similar advantage could also be achieved in a shape of themagnetic recording layer104 having the widest shape at a central portion in its longitudinal direction.FIG. 56C shows a shape obtained by cutting a rugby ball or an oval shape at its both ends, andFIG. 56D shows an octagonal shape.
FIRST EXAMPLE
• Next, a magnetic memory according to first example of the invention will be explained with reference toFIG. 57.FIG. 57 is a diagram showing a constitution of a memory cell in a magnetic memory according to this example. The magnetic memory of the example has a plurality of memory cells, and each memory cell is provided with anMTJ102, awriting wire120, ayoke125, and awriting selecting transistor160.
• TheMTJ102 is provided with amagnetic recording layer104 provided on thewriting wire120, atunnel barrier layer106 provided on themagnetic recording layer104, a magnetization pinnedlayer108 provided on thetunnel barrier layer106, and ananti-ferromagnetic layer110 provided on the magnetization pinnedlayer108. Theyoke125 is provided so as to come in contact with the opposite face of thewriting wire120 from themagnetic recording layer104. Thewriting selecting transistor160 is provided with agate162 which also serves as a word line, asource162, and adrain166. Thewriting wire120 is electrically connected to thesource164 of thewriting selecting transistor160 via theyoke125 and a connectingportion150.
• A writingbit line140 is provided on the opposite side of thewriting wire120 from theyoke125 so as to be approximately perpendicular to thewriting wire120 via an insulating layer (not shown). Thewriting bit line140 is provided just below theMTJ102. Theanti-ferromagnetic layer110 in theMTJ102 is electrically connected to areading bit line145 via a connectingportion142.
• In the example, such a constitution is employed like the first embodiment that end faces of thewriting wire120 and theyoke125 in a direction perpendicular to current flowing in thewriting wire120, and end faces of themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer108, and theanti-ferromagnetic layer110 are positioned on the same plane. Themagnetic recording layer104 in theMTJ102 is arranged to appear in a plan view such that a long side direction of themagnetic recording layer104 is not perpendicular to a direction of the writing current flowing thewriting wire120 but it is inclined thereto, as explained regardingFIG. 55.
• In the magnetic memory of the example thus constituted, writing of data in a memory cell is performed by first turning on thewriting selecting transistor160, thereafter causing writing current to flow thewriting wire120 and thewriting bit line140 to generate writing magnetic field, and reversing magnetic field of themagnetic recording layer104 by the writing magnetic field.
• Reading of data from the memory cell is performed by first turning on thewriting selecting transistor160, thereafter applying a voltage between the readingbit line145 and thedrain166 of thewriting selecting transistor160, and measuring current flowing theMTJ102, or by supplying fixed current one of thereading bit line145 and thedrain166 of thewriting selecting transistor160 to theMTJ102 and measuring a voltage between the readingbit line145 and thedrain166 of thewriting selecting transistor160.
• The magnetic memory according to the example also allows mass storage and high speed writing, of course.
SECOND EXAMPLE
• Next, a second example of the invention will be explained with reference to FIGS.58(a),58(b), and58(c). This example is directed to a method for manufacturing the memory cell in the magnetic memory according to the first example shown inFIG. 57, and manufacturing steps are shown in FIGS.58(a),58(b), and58(c).
• As shown inFIG. 58(a), first, theyoke125, thewriting wire120, themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer8, and theanti-ferromagnetic layer110 are sequentially stacked on a substrate (not shown). Theyoke125 is made of NiFe or CoZrNb in an amorphous state, thewriting wire120 is made of Ru, Cu, or CuNx, themagnetic recording layer104 is made of NiFe, thetunnel barrier layer106 is made of AlOx, themagnetic recording layer108 is made of CoFe, and theanti-ferromagnetic layer110 is made of PtMn.
• Next, the stacked layers of theyoke125, thewriting wire120, themagnetic recording layer104, thetunnel barrier layer106, themagnetic fixing layer108, and theanti-ferromagnetic layer110 are patterned so as be formed in a wiring shape by utilizing a lithography technique (refer toFIG. 58(b)).
• Next, theBTJ102 is formed on thewriting wire120 by patterning themagnetic recording layer104, thetunnel barrier layer110, themagnetic fixing layer108, and the anti-ferromagnetic layer110 (refer toFIG. 58(c)).
• The magnetic memory manufactured by the manufacturing method of this example is constituted like the first embodiment such that end faces of thewriting wire120 and theyoke125 in a direction perpendicular to current flowing thewriting wire120, and end faces of themagnetic recording layer104, thetunnel barrier layer106, the magnetization pinnedlayer108, and theanti-ferromagnetic layer110 are positioned on the same plane. Themagnetic recording layer104 of theMJT102 is arranged to appear in a plan view such that a long side direction of themagnetic recording layer104 is not perpendicular to a direction of the writing current flowing thewriting wire120 but it is inclined thereto, as explained regardingFIG. 55.
• Accordingly, the magnetic memory manufactured by the manufacturing method according to this example also allow mass storage and high speed writing.
• Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concepts as defined by the appended claims and their equivalents.

Claims (34)

1. A magnetic memory comprising:

a magnetoresistance effect element having a magnetization pinned layer whose magnetization direction is pinned, a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the magnetization pinned layer and the storage layer; and

a first wiring layer which is electrically connected to the magnetoresistance effect element and extends in a direction substantially perpendicular to a direction of an easy magnetization axis of the storage layer,

an end face of the magnetoresistance effect element substantially perpendicular to the direction of the easy magnetization axis of the storage layer and an end face of the first wiring layer substantially perpendicular to the direction of the easy magnetization axis being positioned on the same plane.

2. A magnetic memory according toclaim 1, further comprising a first yoke which covers at least a face of the first wiring layer positioned on the opposite side from a face thereof electrically connecting to the magnetoresistance effect element.

3. A magnetic memory according toclaim 2, wherein a direction of an easy magnetization axis of the first yoke and the direction of the easy magnetization axis of the magnetoresistance effect element are substantially perpendicular to each other.

4. A magnetic memory according toclaim 2, wherein a barrier metal layer is provided between the first wiring layer and the first yoke.

5. A magnetic memory according toclaim 1, wherein a thickness of the first wiring layer is 30 nm or less.

6. A magnetic memory according toclaim 1, further comprising a second wiring layer which is connected to a face of the magnetoresistance effect element which is positioned on the opposite side from a face thereof electrically connected to the first wiring layer and extends in the direction crossing a direction in which the first wiring layer extends.

7. A magnetic memory according toclaim 6, further comprising a second yoke which covers at least a face of the second wiring layer positioned on the opposite side from a face thereof electrically connecting to the magnetoresistance effect element.

8. A magnetic memory according toclaim 7, wherein a barrier metal layer is provided between the second wiring layer and the second yoke.

9. A magnetic memory comprising:

a magnetoresistance effect element which has a magnetization pinned layer whose magnetization direction is pinned, a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the magnetization pinned layer and the storage layer, and whose film face shape has a long axis and a short axis; and

a first wiring layer which is electrically connected to the magnetoresistance effect element,

an end face of the magnetoresistance effect element extending along the short axis of the magnetoresistance effect element and a side face of the first wiring layer extending along a longitudinal direction of the first wiring layer being positioned on the same plane.

10. A magnetic memory according toclaim 9, further comprising a first yoke which covers at least a face of the first wiring layer positioned on'the opposite side from a face thereof electrically connecting to the magnetoresistance effect element.

11. A magnetic memory according toclaim 9, wherein a thickness of the first wiring layer is 30 nm or less.

12. A magnetic memory according toclaim 10, wherein a barrier metal layer is provided between the first wiring layer and the first yoke.

13. A magnetic memory according toclaim 9, further comprising a second wiring layer which is connected to a face of the magnetoresistance effect element which is positioned on the opposite side from a face thereof electrically connected to the first wiring layer and extends in a direction crossing a direction in which the first wiring layer extends.

14. A magnetic memory according toclaim 13, further comprising a second yoke which covers at least a face of the second wiring layer positioned on the opposite side from a face thereof electrically connecting to the magnetoresistance effect element.

15. A magnetic memory according toclaim 14, wherein a barrier metal layer is provided between the second wiring layer and the second yoke.

16. A method for manufacturing a magnetic memory comprising:

stacking a magnetoresistance effect film which serves as a magnetoresistance effect element and comprises a first magnetic layer serving as a magnetization pinned layer whose magnetization direction is pinned, a second magnetic layer serving as a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the first magnetic layer and the second magnetic layer to serve as a tunnel barrier layer, and a wiring film serving as a wire; and

patterning the magnetoresistance effect film and the wiring film such that an end face of the magnetoresistance effect element substantially perpendicular to a direction of an easy magnetization axis of the storage layer and an end face of the wiring film substantially perpendicular to the direction of the easy magnetization axis are positioned on the same plane.

17. A method for manufacturing a magnetic memory comprising:

stacking a magnetoresistance effect film which serves as a magnetoresistance effect element and comprises a first magnetic layer serving as a magnetization pinned layer whose magnetization direction is pinned, a second magnetic layer serving as a storage layer whose magnetization direction is changeable, and a non-magnetic layer provided between the first magnetic layer and the second magnetic layer to serve as a tunnel barrier layer and whose film face shape has a long axis and a short axis, and a wiring film serving as a wire; and

patterning the magnetoresistance effect film and the wiring film such that an end face of the magnetoresistance effect element extending along the short axis of the magnetoresistance effect element and a side face of the wiring layer extending along a longitudinal axis of the wire are positioned on the same plane.

18. A magnetic memory which has memory cells, each comprising:

a storage element having a magnetic recording layer whose magnetization direction changes according to external magnetic field, a magnetization pinned layer whose magnetization direction is pinned, and a non-magnetic layer provided between the magnetic recording layer and the magnetization pinned layer;

a writing wire which is provided on the opposite side of the magnetic recording layer from the non-magnetic layer and in which writing current flows; and

a yoke which is provided on the opposite side of the writing wire from the magnetic recording layer,

a pair of opposed side faces of the storage element being positioned on the same plane as a pair of opposed side faces of each of the writing wire and the yoke, and

a relative magnetic permeability of the magnetic recording layer being 5 or more.

19. A magnetic memory according toclaim 18, wherein a longitudinal axis of the magnetic recording layer is inclined to a direction perpendicular to a direction in which the writing wire extends by an angle of 45°.

20. A magnetic memory according toclaim 18, wherein a plan shape of the magnetic recording layer is asymmetrical regarding a direction perpendicular to a direction in which the writing wire extends.

21. A magnetic memory according toclaim 18, wherein a plan shape of the magnetic recording layer has the maximum width at a central portion thereof in a direction perpendicular to a direction in which the writing wire extends.

22. A magnetic memory according toclaim 18, wherein a relative magnetic permeability of the yoke is in a range of 80 or more and 120 or less.

23. A magnetic memory according toclaim 18, wherein the yoke is formed of material with a high melting point.

24. A magnetic memory according toclaim 18, where the memory cell is provided with a selecting transistor which selects the memory cell.

25. A magnetic memory which has memory cells, each comprising:

a storage element having a magnetic recording layer whose magnetization direction changes according to external magnetic field, a magnetization pinned layer whose magnetization direction is pinned, and a non-magnetic layer provided between the magnetic recording layer and the magnetization pinned layer;

a writing wire which is provided on the opposite side of the magnetic recording layer from the non-magnetic layer and in which writing current flows; and

a yoke which is provided on the opposite side of the writing wire from the magnetic recording layer,

a longitudinal axis of the magnetic recording layer being inclined to a direction perpendicular to a direction in which the writing wire extends by an angle of more than 0° and less than 90°, and

a relative magnetic permeability of the magnetic recording layer being 5 or more.

26. A magnetic memory according toclaim 25, wherein a longitudinal axis of the magnetic recording layer is inclined to a direction perpendicular to a direction in which the writing wire extends by an angle of 45°.

27. A magnetic memory according toclaim 25, wherein a pair of opposed side faces of the storage element are positioned on the same plane as a pair of opposed side faces of each of the writing wire and the yoke.

28. A magnetic memory according toclaim 25, wherein a plan shape of the magnetic recording layer is asymmetrical regarding a direction perpendicular to a direction in which the writing wire extends.

29. A magnetic memory according toclaim 25, wherein a plan shape of the magnetic recording layer has the maximum width at a central portion thereof in a direction perpendicular to a direction in which the writing wire extends.

30. A magnetic memory according toclaim 25, wherein a relative magnetic permeability of the yoke is in a range of 80 or more and 120 or less.

31. A magnetic memory according toclaim 25, wherein the yoke is formed of material with a high melting point.

32. A magnetic memory according toclaim 25, where the memory cell is provided with a selecting transistor which selects the memory cell.

33. A magnetic memory which has memory cells, each comprising:

a storage element having a magnetic recording layer whose magnetization direction changes according to external magnetic field, a magnetization pinned layer whose magnetization direction is pinned, and a non-magnetic layer provided between the magnetic recording layer and the magnetization pinned layer;

a writing wire which is provided on the opposite side of the magnetic recording layer from the non-magnetic layer and in which writing current flows; and

a yoke which is provided on the opposite side of the writing wire from the magnetic recording layer,

a longitudinal axis of the magnetic recording layer being inclined to a direction perpendicular to a direction which the writing wire extends by an angle of more than 0° and less than 90°, and

a pair of opposed side faces of the storage element being positioned on the same plane as a pair of opposed side faces of each of the writing wire and the yoke.

34. A magnetic memory according toclaim 33, where the memory cell is provided with a selecting transistor which selects the memory cell.

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