BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a supporting plate which is used when a substrate such as a semiconductor wafer is thinned, and also relates to an apparatus and a method for stripping the supporting plate from the semiconductor wafer.
2. Description of the Prior Art
There is a continuing need to make IC cards and cell phones thinner, smaller, and lighter. In order to satisfy this need, semiconductor chips to be incorporated therein must be thin. Although at present the thickness of a wafer which forms a semiconductor chip is 125-150 μm, it is expected that the thickness of a semiconductor wafer must be 25-50 μm for a next generation of chips.
An example of a conventional method for thinning a semiconductor wafer is shown inFIG. 8. Specifically, a protecting tape is attached to a surface (A-surface) of a semiconductor wafer on which a circuit (element) has been formed. The wafer is turned over, and the rear surface (B-surface) of the semiconductor wafer is ground by a grinder to make the wafer thinner. The B surface of the semiconductor wafer which has been thinned is fixed onto a dicing tape retained by a dicing frame, and the protecting tape covering the surface (A-surface) of the semiconductor wafer on which a circuit (element) has been formed is stripped in this state. Next, the wafer is cut into each chip by a dicing device.
The above-mentioned method has been disclosed inDocument 1. According toDocument 1, the heat-resistant protecting tape is stripped from the thinned semiconductor wafer by using a strong adhesive tape bonded to one end of the protecting tape.
Document 2 has disclosed that a protecting base obtained by immersing a ladder-type silicone oligomer in an aluminum nitride—boron nitride porous sintered material is used instead of a protecting tape, and the protecting base and a semiconductor wafer are bonded by using a thermoplastic film.Document 2 also mentions that they are immersed in pure water at 80° C. for 3 hours before stripping.
Document 3 has disclosed that a protecting base is made of a material having the same thermal expansion coefficient as a semiconductor wafer such as alumina, aluminum nitride, boron nitride, or silicon carbide.
Also,Document 3 has proposed a method in which the protecting base and the semiconductor wafer are bonded by using a thermoplastic resin such as polyimide, the semiconductor wafer is thinned by a grinder, and thereafter stripping is performed by immersing in water, amine, or a mixed solution of water and amine, or by using steam.
[Document 1] Japanese Patent Application Publication No. 2002-270676
[Document 2] Japanese Patent Application Publication No. 2002-203821
[Document 3] Japanese Patent Application Publication No. 2001-77304
In the above-mentioned techniques, since it is difficult for a solvent to enter between the supporting plate (protecting tape) and the semiconductor wafer when the supporting plate (protecting tape) is stripped from the semiconductor wafer, it takes too much time to strip the supporting plate from the semiconductor wafer.
Also, the thermoplastic film bonding the support plate (protecting tape) and the semiconductor wafer often fails to completely dissolve, and tends to be left in a state of sticking to either the support plate or the semiconductor wafer.
If an adhesive is left as described above, cracking or chipping of the semiconductor wafer easily occurs at the time of stripping.
In order to solve the above problem, the present applicant has proposed a supporting plate in which a plurality of penetrating holes are provided in the thickness direction of the supporting plate.FIG. 9 explains a method for stripping this supporting plate.
According to this method, asolvent supplying plate102 is laid onto the upper surface of a supportingplate100 via an O-ring101. Next, a solvent is supplied from asolvent supplying pipe103 to a space S surrounded by the supportingplate100, the O-ring101 and thesolvent supplying plate102. The solvent passes through penetratingholes104 formed in the supportingplate100, dissolves and removes anadhesive layer105.
With the method of using a supporting plate in which a plurality of penetrating holes are provided, it is possible to securely remove an adhesive in a short period of time. However, another problem arises.
As shown inFIG. 10, the solvent leaks from the periphery of the supporting plate to the outside, and the solvent drops onto the dicing tape, which results in a deterioration of the dicing tape in a short period of time.
Further, efficiency of stripping is bad because part of a new solvent supplied to the space S is withdrawn without being utilized.
Furthermore, even if the adhesive is completely dissolved, if a finger or the like is used as a device for stripping the semiconductor wafer from the supporting plate, there is a strong likelihood that the circuit-formed surface of the semiconductor wafer will be damaged.
In order to solve the above-mentioned problems, the object of the present invention is to provide a supporting plate which makes it possible to easily strip the supporting plate from a substrate in a short period of time after thinning the substrate, and an apparatus and a method for stripping the supporting plate.
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, there is provided a supporting plate to which a circuit-formed surface of a substrate is bonded with an adhesive, wherein a first penetrating hole is formed in a substantially central portion of the supporting plate in the thickness direction, grooves connecting with the first penetrating hole are formed on a surface of the supporting plate to be contacted with an adhesive, and a second penetrating hole connecting with the grooves is formed in a peripheral portion of the supporting plate in the thickness direction.
Since the supporting plate of the present invention has a first penetrating hole formed in a substantially central portion of the supporting plate in the thickness direction, grooves formed on a surface of the supporting plate to be contacted with an adhesive so as to connect with the first penetrating hole, and a second penetrating hole formed in a peripheral portion of the supporting plate in the thickness direction so as to connect with the grooves, it is possible to use the first penetrating hole as a hole for supplying a solvent and the second penetrating hole as a hole for draining the solvent. With this, when the supporting plate is stripped from the substrate after the substrate is thinned, it is possible to supply the solvent quickly to the whole surface of the adhesive which bonds the substrate and the supporting plate so as to strip the supporting plate in a short period of time.
Also, if the second penetrating hole is used as a hole for supplying a solvent and the first penetrating hole is used as a hole for draining the solvent, the same effect can be achieved.
There is also provided an apparatus for stripping a supporting plate bonded to a circuit-formed surface of a substrate with an adhesive, comprising a plate which has a first penetrating hole formed in a substantially central portion of the plate in the thickness direction, a second penetrating hole formed in a peripheral portion of the plate in the thickness direction, and a hole for attracting a supporting plate formed between the first penetrating hole and the second penetrating hole in the radial direction.
Since the stripping apparatus of the present invention comprises a plate which has a first penetrating hole formed in a substantially central portion of the plate in the thickness direction, a second penetrating hole formed in a peripheral portion of the plate in the thickness direction, and a hole for attracting a supporting plate formed between the first penetrating hole and the second penetrating hole in the radial direction, it is possible to use the first penetrating hole as a hole for supplying a solvent and the second penetrating hole as a hole for draining the solvent. With this, when the supporting plate is stripped from the substrate after the substrate is thinned, it is possible to supply the solvent quickly to the whole surface of the adhesive which bonds the substrate and the supporting plate so as to strip the supporting plate in a short period of time.
Also, if the second penetrating hole is used as a hole for supplying a solvent and the first penetrating hole is used as a hole for draining the solvent, the same effect can be achieved.
There is also provided a method for stripping a supporting plate bonded to a circuit-formed surface of a substrate with an adhesive, comprising the steps of supplying a solvent from outside to a first penetrating hole of a plate, distributing the solvent from a first penetrating hole of a supporting plate to grooves connecting with the first penetrating hole of the supporting plate, dissolving the adhesive on a surface contacted with the substrate by the solvent, and draining the solvent used for dissolving the adhesive from a second penetrating hole of the supporting plate and a second penetrating hole of the plate.
Since the stripping method of the present invention comprises the steps of supplying a solvent from outside to a first penetrating hole of a plate, distributing the solvent from a first penetrating hole of a supporting plate to grooves connecting with the first penetrating hole of the supporting plate, dissolving the adhesive on a surface contacted with the substrate by the solvent, and draining the solvent used for dissolving the adhesive from a second penetrating hole of the supporting plate and a second penetrating hole of the plate, it is possible to supply the solvent quickly to the whole surface of the adhesive which bonds the substrate and the supporting plate so as to strip the supporting plate in a short period of time.
There is also provided a method for stripping a supporting plate bonded to a circuit-formed surface of a substrate with an adhesive, comprising the steps of supplying a solvent from outside to a second penetrating hole of a plate, distributing the solvent from a second penetrating hole of a supporting plate to grooves connecting with the second penetrating hole of the supporting plate, dissolving the adhesive on a surface contacted with the substrate by the solvent, and draining the solvent used for dissolving the adhesive from a first penetrating hole of the supporting plate and a first penetrating hole of the plate.
Since the stripping method of the present invention comprises the steps of supplying a solvent from outside to a second penetrating hole of a plate, distributing the solvent from a second penetrating hole of a supporting plate to grooves connecting with the second penetrating hole of the supporting plate, dissolving the adhesive on a surface contacted with the substrate by the solvent, and draining the solvent used for dissolving the adhesive from a first penetrating hole of the supporting plate and a first penetrating hole of the plate, it is possible to supply the solvent quickly to the whole surface of the adhesive which bonds the substrate and the supporting plate so as to strip the supporting plate in a short period of time.
BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a schematic view showing an embodiment of a supporting plate according to the present invention;
FIG. 2 shows the process for forming a supporting plate;
FIG. 3 is an enlarged view explaining staggered grooves;
FIG. 4 is an enlarged view explaining honeycomb-shaped grooves;
FIG. 5 is a schematic view showing an embodiment of an apparatus for stripping a supporting plate;
FIG. 6 is a perspective view ofFIG. 5;
FIG. 7 is a view showing another embodiment of the apparatus for stripping a supporting plate;
FIG. 8 is a view explaining a conventional method for stripping a supporting plate;
FIG. 9 is a view explaining the conventional method for stripping a supporting plate, and
FIG. 10 is a view explaining a drawback of the conventional art for stripping a supporting plate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the attached drawings.FIG. 1 is a schematic view showing an embodiment of a supporting plate according to the present invention, andFIG. 2 shows the process for forming a supporting plate.
A supportingplate1 according to the present invention shown inFIG. 1 is made of a glass plate, a ceramic plate or a metal plate.
A circuit-formed surface of a semiconductor wafer W is bonded to one of the surfaces of the supportingplate1 by using an adhesive, which is not shown in the drawing.
According to the present invention, the supportingplate1 has a unique structure as described below.
A firstpenetrating hole2 is formed in a substantially central portion (center) of the supportingplate1 so as to penetrate in the thickness direction. A plurality of first penetratingholes2 may be formed, and for example, four penetratingholes2 are formed inFIG. 1. However, the number of the penetratingholes2 is not limited to this.
Also,grooves3 connecting with the firstpenetrating hole2 are formed on the surface of the supporting plate to which a semiconductor wafer W is bonded. Thegrooves3 are formed so as to cover almost all the surface up to the outer periphery. As an example, thegrooves3 have a depth of 0.3 mm in a case where the supportingplate1 has a thickness of 0.7 mm. The depth of thegrooves3 needs to be sufficient so as not to be filled with an adhesive layer interposed between the supportingplate1 and the semiconductor wafer W for bonding. With this, a small gap is defined between the adhesive layer and thegrooves3, so that a solvent can quickly flow along the gap when the solvent is supplied as described below.
A secondpenetrating hole4 is formed in a peripheral portion of the supportingplate1. The secondpenetrating hole4 penetrates in the thickness direction and connects with thegrooves3 so as to drain a solvent to outside (for withdrawal). It is possible to provide a plurality of penetratingholes4 in a peripheral portion of the supportingplate1.
With the above-mentioned structure, the firstpenetrating hole2 to supply a solvent from outside and the secondpenetrating hole4 to discharge a solvent to outside are connected to each other via thegrooves3.
Thegrooves3 are formed in a grid pattern, part of which is shown in the enlarged view ofFIG. 1. Thegrooves3 serve to connect the firstpenetrating hole2 and the secondpenetrating hole4 as mentioned above. Therefore, if a solvent is supplied from outside to the firstpenetrating hole2, the solvent flows from the central portion to the periphery (outer periphery) portion along thegrooves3, and reaches the secondpenetrating hole4.
The process for forming the supportingplate1 provided with thegrooves3 will be described below with reference toFIG. 2.
First, a glass plate is prepared, and a dry film resist is applied to a surface of the plate where thegrooves3 are to be formed (Step1).
An exposure step and a development step are performed to the dry film resist by using a grid-patterned photo mask (SeeSteps2 and3).
With these steps, the grid-patterned dry film resist (a resist mask for forming the grooves3) is formed on the surface of the glass plate.
Next, a protection step is performed to the periphery, and thereafter, cutting of the glass plate is performed by a sandblasting method with the grid-patterned dry film resist as a mask (SeeSteps4 and5).
With these steps, the grid-patternedgrooves3 are formed on the surface of the glass plate, which have a predetermined depth from the surface.
Next, a dry film resist is applied to the other surface of the glass plate (See Step6).
An exposure step and a development step are performed to the dry film resist by using a photo mask for forming the firstpenetrating hole2 and the second penetrating hole4 (SeeSteps7 and8).
With these steps, the dry film resist corresponding to the firstpenetrating hole2 and the second penetrating hole4 (a resist mask for forming the firstpenetrating hole2 and the second penetrating hole4) is formed on the other surface of the glass plate.
Next, a protection step is performed to the periphery (Step9), and thereafter, cutting of the glass plate is performed by a sandblasting method with the resist mask for forming the firstpenetrating hole2 and the second penetrating hole4 (Step10).
Next, cleaning is performed to the glass plate (Step11). With these steps, the firstpenetrating hole2 is formed in the central portion of the glass plate, which penetrates in the thickness direction. The secondpenetrating hole4 is formed in the periphery portion, which penetrates in the thickness direction.
In the process shown inFIG. 2, thegrooves3 are formed first, and the firstpenetrating hole2 and the secondpenetrating hole4 are formed next. However, this order may be reversed.
A dry etching method or a wet etching method may be used to form grid-patterned grooves instead of a sandblasting method. However, when these etching methods are used, it is difficult to form uniform grooves compared to a sandblasting method although it depends on the width or the depth of the grooves. A sandblasting method is preferred to form thegrooves3.
In the supportingplate1 of the present embodiment, the penetratinghole2 for supplying a solvent from outside is formed in the central portion of the supportingplate1 in the thickness direction, the grid-patterned grooves connecting with the firstpenetrating hole2 are formed on a surface of the supporting plate to be contacted with an adhesive, and the secondpenetrating hole4 for draining a solvent to outside connecting with thegrooves3 is formed in the peripheral portion of the supportingplate1 in the thickness direction. Therefore, when the supportingplate1 is stripped from the semiconductor wafer W by using the stripping apparatus and a stripping method described below, it is possible to supply a solvent quickly to the whole surface of the adhesive which bonds the wafer W and the supportingplate1 so as to strip the supportingplate1 in a short period of time compared to the case of using a conventional supporting plate.
More specifically, since a conventional supporting plate has a structure in which a number of penetrating holes are formed in the thickness direction, dissolution of the adhesive starts in the area where the adhesive contacts with the penetrating holes. Therefore, it takes time to distribute the solvent over the adhesive uniformly.
In contrast, the supportingplate1 according to the present embodiment has a structure in which the grid-patternedgrooves3 are formed on almost all the surface to be contacted with the adhesive. Therefore, the solvent supplied from the firstpenetrating hole2 flows toward the periphery portion via the grid-patternedgrooves3 connecting with the firstpenetrating hole2, so that the solvent can be distributed quickly over the adhesive.
Consequently, it is possible to strip the supportingplate1 in a short period of time compared to a conventional supporting plate.
Further, since a number of penetrating holes are not formed in the supportingplate1 according to the present invention, unlike a conventional supporting plate, when the supportingplate1 is stripped from thesemiconductor wafer W1 by using the stripping apparatus and method described below, it is possible to retain the area where no hole is formed by vacuum attraction. With this, it is possible to simplify the process for stripping the supportingplate1 from the semiconductor wafer W.
Furthermore, since a number of penetrating holes are not formed in the supportingplate1 according to the present invention, unlike a conventional supporting plate, it is possible to improve the strength of the supportingplate1, and increase the reuse rate.
Also, according to the present invention, since an excessive amount of force is not exerted on the semiconductor wafer W when the supportingplate1 is stripped from the wafer W, there is little likelihood that cracking or chipping will occur in the wafer W.
Consequently, in the semiconductor wafer W to which the supportingplate1 is attached, it is possible to utilize the surface ground by a grinder after thinning the wafer W as a second circuit-formed surface, for example.
Next, another embodiment of the supportingplate1 will be described below.
The shape of thegrooves3 is a grid in the above-mentioned embodiment of the supportingplate1. However, the shape of thegrooves3 may be staggered (see the enlarged view of the grooves shown inFIG. 3(a) and the enlarged view of the periphery shown inFIG. 3(b)).
More specifically, the shape of thegrooves3 according to this embodiment is formed by staggering grid-patternedgrooves3 as shown inFIG. 1 in columns at a predetermined interval.
Thestaggered grooves3 make it possible to supply the solvent quickly to the whole surface of the adhesive which bonds the wafer W and the supportingplate1 in the same manner as the case of the grid-patternedgrooves3. Consequently, it is possible to strip the supportingplate1 from the substrate in a short period of time compared to the case of using a conventional supporting plate.
Incidentally, thestaggered grooves3 can be formed in the same process shown inFIG. 2.
Next, another embodiment of the supporting plate will be described below.
The shape of thegrooves3 is honeycombed according to this embodiment. More specifically, the shape of thegrooves3 is hexagonal (see the enlarged view of the grooves shown inFIG. 4(a) and the enlarged view of the periphery shown inFIG. 4(b)).
In the case where the shape of thegrooves3 is hexagonal, it is possible to supply the solvent more quickly to the whole surface of the adhesive which bonds the wafer W and the supportingplate1 compared to the cases of the grid-patternedgrooves3 and thestaggered grooves3. Consequently, it is possible to strip the supportingplate1 from the substrate in a shorter period of time compared to the case of using a conventional supporting plate.
One of the reasons is that the solvent supplied from the central portion can more easily reach the peripheral portion compared to the cases of the grid-patternedgrooves3 and thestaggered grooves3, by arranging each of the adjacenthexagonal grooves3 to be directed from the central portion to the peripheral portion.
Thehexagonal grooves3 can be formed in the same processes shown inFIG. 2.
As for the shape of thegrooves3, it is also possible to employ a coil shape in which the grooves are directed from the hole for supplying a solvent in the center toward the hole for draining the solvent in the periphery.
Also, the supporting plate may be comprised of frosted glass as follows:
Specifically, the surface of the glass substrate to which the semiconductor wafer W is attached is roughened by 0.05 mm-0.1 mm, although this is not shown in the drawings. Since the other features are the same as described above, they are not explained again.
In this supporting plate, a solvent supplied from the firstpenetrating hole2 can permeate the whole surface by capillary action. With this, it is possible to achieve the same function as the case of the supporting plate provided with thegrooves3 described above.
Next, an embodiment of the apparatus and the method of stripping the supporting plate having the above-mentioned structure from the semiconductor wafer W will be described with reference toFIGS. 5 and 6.
In this embodiment, the supportingplate1 is provided with thehexagonal grooves3 shown inFIG. 4, for example.
The stripping apparatus20 according to the present embodiment comprises aplate10. Theplate1 is supported by an elevator mechanism so as to be elevated or lowered in the vertical direction by a predetermined stroke.
A first penetrating hole12 (for supplying a solvent from outside) is formed in the central portion of theplate10, and a second penetrating hole14 (for draining a solvent to outside) is formed in the periphery portion of theplate10. Also, ahole13 is formed between the first penetratinghole12 and the second penetratinghole14 in the radial direction. Thehole13 is used for vacuuming, and a recessedportion15 is formed at the end of thehole13 which is in contact with the supportingplate1. The first penetratinghole12 is connected to a solvent supplying means, for example, by a tube which is not shown in the drawings.
When the supportingplate1 and the semiconductor wafer W bonded to the supportingplate1 are attracted to theplate10 having the above-mentioned structure by vacuum attraction using thehole13, the hole for supplying a solvent12 is coupled to the firstpenetrating hole2 of the supportingplate1 and the hole for draining a solvent14 is coupled to the secondpenetrating hole4 of the supportingplate1. Also, thehole13 is positioned in an area of the supportingplate1 where the firstpenetrating hole2 and the secondpenetrating hole4 are not formed.
Next, stripping the supportingplate1 from the semiconductor wafer W by using the stripping apparatus20 will be described.
Theplate10 is pushed onto the upper surface of the supportingplate1, so that the hole for supplying a solvent12 of theplate10 is aligned (coupled) to the firstpenetrating hole2 of the supportingplate1, and the hole for draining a solvent14 is aligned (coupled) to the secondpenetrating hole4 of the supporting plate1 (seeFIG. 5).
A solvent is supplied to the hole for supplying a solvent12 of theplate10 by a solvent supplying means (not shown in the drawing) in this state.
The solvent flows toward the firstpenetrating hole2 of the supportingplate1, and reaches thehexagonal grooves3 which connect with the penetratinghole2.
In this instance, as described above, since thegrooves3 are formed so as to cover almost all surface of the supportingplate1 up to the outer periphery, the solvent can be distributed quickly over anadhesive layer5 so as to dissolve theadhesive layer5.
The solvent used for dissolving theadhesive layer5 flows to the secondpenetrating hole4 formed in the periphery of the supportingplate1 and connecting with thegrooves3, reaches the hole for draining a solvent14 of theplate10, and is drained to outside (and withdrawn).
Next (after a predetermined period of time passes), the supportingplate1 is stripped from the semiconductor wafer W.
In this instance, the pressure inside the recessedportion15 is reduced by thehole13 for vacuuming, and theplate10 is lifted up in the state where the supportingplate1 is attracted to theplate10 by vacuuming. In this way, the supportingplate1 is stripped and the semiconductor wafer W is left to adicing tape7. Incidentally, the dicingtape7 has adhesiveness and is retained by aframe6.
According to the present embodiment of the stripping apparatus and the stripping method, the solvent supplied to the hole for supplying a solvent12 of theplate10 flows toward the firstpenetrating hole2 of the supportingplate1, and reaches the periphery of the supportingplate1 via thehexagonal grooves3 which connect with the penetratinghole2 of the supportingplate1. The solvent flows to the hole for draining a solvent14 of theplate10 via the secondpenetrating hole4 formed in the periphery of the supportingplate1 to be drained to outside.
As described above, thegrooves3 make it possible to supply the solvent quickly to the whole surface of theadhesive layer5. Consequently, it is possible to strip the supportingplate1 in a shorter period of time compared to the case of using the conventional supporting plate.
Incidentally, when the supportingplate1 is stripped from the semiconductor wafer W, there are cases where the supportingplate1 is still attached to the semiconductor wafer W due to surface tension of the solvent used for dissolving theadhesive layer5, which makes it difficult to strip the supportingplate1.
In these cases, it is possible to make the supportingplate1 easier to strip by cancelling (breaking) the surface tension with air supplied from the solvent supplying hole of theplate10 to the firstpenetrating hole2 of the supportingplate1.
In order to achieve this method, an air supplying means may be provided in a stripping apparatus having the above-mentioned structure, and a tube of the air supplying means may be connected to a tube of the solvent supplying means which leads to the solvent supplying hole of theplate10.
In the above-mentioned embodiments, a solvent is supplied to the central portion and drained from the periphery portion. However, it is also possible to supply a solvent to the periphery portion and drain from the central portion.
In this instance, the secondpenetrating hole4 formed in the periphery portion of the supportingplate1 is used for supplying a solvent from outside, and the firstpenetrating hole2 formed in the central portion of the supportingplate1 is used for draining the solvent to the outside.
Also, in theplate10 of the stripping apparatus20, thehole14 formed in the periphery portion is used for supplying a solvent from outside, and thehole12 formed in the central portion is used for draining the solvent to the outside.
Since the other features are the same as mentioned above, they are not explained again.
It should be noted that the same function can be achieved in the above-mentioned case as in the case where a solvent is supplied to the central portion and drained from the periphery portion.
In the stripping apparatus20 according to the present embodiment, theplate10 is provided in the upper surface of the supportingplate1 as shown inFIG. 5. However, theplate10 may be provided in the lower surface of the supportingplate1 as shown inFIG. 7.
In this instance, it is not necessary to form thesolvent draining hole14 although the solvent supplyinghole12 is formed in theplate10.
The present invention is not limited to the above-mentioned embodiments, and other various structures are possible within the scope of the present invention.
Effect of the Invention According to the present invention, a solvent can be supplied to the whole surface of the adhesive which bonds the substrate and the supporting plate so as to strip the supporting plate in a short period of time and reduce the treatment time.
Accordingly, it is possible to achieve a supporting plate, an apparatus and a method for stripping a supporting plate suitable for reducing the treatment time with high reliability.