US20040246010A1 - Probe tip in single-sided compliant probe apparatus - Google Patents

Abstract

A single-sided compliant probe is provided that includes a conductive tip shaped as one or more thin conductive fins having one edge which is positioned on a supporting substrate in a manner that allows the opposing edge to engage a contact pad and to move flexibly with respect to the supporting substrate while in close proximity to adjacent probes in an array. The probe tip is oriented in a direction of wipe of the tip across the contact pad but moves substantially vertically in response to the force of a mating contact pad as it is mechanically biased against the tip. Mechanical compliance of the probe allows electrical contact to be made reliably between the probe and its corresponding contact pad on a microelectronic device, where the mechanical compliance accommodates variations in height of the contact pad and wipe improves reliability of electrical engagement.

Description

BACKGROUND OF THE INVENTION
• This invention relates to burn-in and test of microelectronic devices, specifically to contact assemblies used for connecting electrical signals to integrated circuits during burn-in and test of individual chips and of full wafers.[0001]
• Microelectronic devices are subjected to a series of test procedures during the manufacturing process in order to verify functionality and reliability. The testing procedures conventionally include wafer probe testing, in which microelectronic device chips are tested to determine operation of each chip before it is diced from the wafer and packaged. Probe cards built of long cantilever wires are used to test one or several chips at a time while on the wafer.[0002]
• Typically, not all chips on a wafer are found to be operable in the wafer probe test, resulting in a yield of less than 100% good devices. The wafer is diced into individual chips, and the good chips are then assembled into packages. The packaged devices are dynamically burned-in by loading them into sockets on burn-in boards and electrically operating them at a temperature of from 125° C. to 150° C. for a burn-in period of 8 to 72 hours in order to induce any defective devices to fail. Burn-in accelerates failure mechanisms that cause infant mortality or early failure of the devices, and allows these defective devices to be weeded out by a functional electrical test before they are used commercially.[0003]
• A full functional test is done on packaged devices, which are operated at various speeds in order to categorize each by maximum speed of operation. Testing discrete packaged devices also permits elimination of any devices that failed during the burn-in process. Burn-in and test of packaged devices is accomplished by means of sockets specially suited to the burn-in conditions and to high speed testing respectively. Conventional manufacturing processes are expensive and time consuming because of a repeated handling and testing of individual discrete devices through a lengthy set of steps that adds weeks to the total manufacturing time for the device.[0004]
• A considerable advantage in cost and in process time can be obtained by burn-in and test of the wafer before it is diced into discrete devices. Additional savings can be obtained by fabricating chip size packages on each device on a wafer before the wafer is diced into discrete devices. A considerable effort has been expended by the semiconductor industry to develop effective methods for wafer level burn-in and test in order to gain benefits of a greatly simplified and shortened process for manufacturing microelectronic devices. In order to reap these benefits, it is necessary to provide means to burn-in and speed test chips before they are diced from the wafer into individual discrete devices.[0005]
• Conventional cantilever wire probes are not suited to burn-in and speed test of devices on the wafer. Cantilever wire probes are too long and costly to allow simultaneous contact to all of the devices on a wafer, as required for simultaneous burn-in of all of the devices on the wafer. In addition, long cantilever wire probes are not suitable for functional testing of high-speed devices because of a high self and mutual inductance of the long, parallel wires comprising the probes.[0006]
• A small, high-performance probe that can be made at low cost is required for practical application of wafer burn-in and test procedures. To be useful for wafer burn-in and test, the probes must reliably contact all of the pads on the devices under test while they are on the undiced wafer. Probes for contacting the wafer must provide electrical contact to pads on devices where the pads vary in height on the surface of the wafer. In addition, the probes must break through any oxide layers on the surface of the contact pads in order to make a reliable electrical contact to each pad. Many approaches have been tried to provide a cost-effective and reliable means to probe wafers for burn-in and test, without complete success.[0007]
• A number of attempts have been tried to provide small, vertically compliant probes for contacting reliably the pads on devices on a wafer. According to the invention represented by U.S. Pat. No. 4,189,825, to David R. Robillard and Robert L. Michaels, a cantilever probe is provided for testing integrated circuit devices. In FIG. 1, cantilever[0008]28 supportssharp tips26 abovealuminum contact pads24 on achip23. Acompliant member25 is urged downward to movetips26 into contact withpads24. An aluminum oxide layer onpad24 is broken bysharp tip26 in order to make electrical contact betweentip24 and the aluminum metal ofpad24. The rigidity of small cantilever beams is generally insufficient to apply the force to a tip that is necessary to cause it to break through an aluminum oxide layer on a contact pad, without an external means of applying force to the cantilever. Cantilever beams of glass, silicon, ceramic material, and tungsten have been tried in various configurations, without success in providing burn-in probes of sufficient force and flexibility.
• A flexible membrane probe shown in FIG. 2A is described in Flexible Contact Probe, IBM Technical Disclosure Bulletin, October 1972, page 1513. A flexible[0009]dielectric film32 includesterminals33 that are suited to making electrical contact with pads on integrated circuits.Terminals33 are connected to test electronics by means offlexible wires34 attached tocontact pads35 onterminals33. Probes fabricated on a flexible polyimide sheet were described in the Proceedings of the IEEE International Test Conference (1988) by Leslie et al. The flexible sheet allows a limited amount of vertical motion to accommodate variations in height of bond pads on integrated circuits on a wafer under test. Membrane probes such as that described by Leslie et al provide connections to integrated circuit chips for high performance testing. However, dimensional stability of the membrane is not sufficient to allow contacts to pads on a full wafer during a burn-in temperature cycle.
• Fabrication of the contacts on a thin silicon dioxide membrane is shown in FIG. 2B as described in U.S. Pat. No. 5,225,771 by Glenn J. Leedy. A[0010]silicon dioxide membrane40 has better dimensional stability than polyimide, thereby somewhat ameliorating the dimensional stability problem of mating contacts to pads on a wafer under test.Probe tips41 are connected byvias44 throughmembrane40 tocircuit traces45 that are linked to an additional layer of circuitry42 above adielectric film43. Limited vertical compliance of the test probes onsilicon dioxide membrane40 renders use of probe arrays unreliable for use in burn-in of devices on a semiconductor wafer.
• Fabrication of an array of burn-in probes on a semiconductor wafer is described in U.S. Pat. No. 4,585,991, as illustrated in FIGS. 3A and 3B showing a top plan view and a sectional view respectively.[0011]Probe51 is a pyramid attached tosemiconductor wafer substrate52 byarms54.Material53 is removed from thesemiconductor wafer52 in order to isolate mechanically theprobe51. A probes as in FIG. 3A provides a limited vertical movement but do not allow space on the substrate for wiring needed to connect an array of probes to test electronics required for dynamic burn-in.
• An approach to providing flexible probes to device contact pads involves the use of flexible wires or posts to connect test circuitry to pads on a chip. A flexible probe shown in FIG. 4A is described in U.S. Pat. No. 5,977,787 by Gobina Das et al. Probe[0012]60 is a buckling beam, generally described in U.S. Pat. No. 3,806,801 by Ronald Bove.Probe60 is adapted for use in burn-in of devices on a wafer.Probe60 is held byguides61 and62 that have a coefficient of expansion similar to that of the wafer being tested.Probe60 is offset by asmall distance63 to provide a definite modality of deflection. Although buckling beams are well suited to testing individual integrated circuit chips, they are too expensive to be used for wafer burn-in where thousands of contacts are required. Further, electrical performance of buckling beam probes is limited because of the length required for adequate flexure of the beam.
• Another approach using flexible posts is shown in FIG. 4B as disclosed in U.S. Pat. No. 5,513,430 by Arnold W. Yanof and William Dauksher. FIG. 4[0013]bshows flexible probes in the form ofposts66 that are able to bend in response to force onprobe tip67.Posts66 are formed at an angle to asubstrate69 in order to allow them to flex vertically in response to a force ontip67 from mating contact pads.Posts66 have ataper65 from thebase terminal68 to tip67 in order to facilitate flexure.
• Yet another approach using flexible wires and posts is shown in FIG. 4C as disclosed in U.S. Pat. No. 5,878,486 by Benjamin N. Eldridge, et al. The probe shown in FIG. 4C comprises a[0014]probe tip72 on aspring wire71 that is bent to a specific shape in order to facilitate flexure.Wire71 is joined tosubstrate74 by aconventional wire bond73. Probes of the type shown in FIG. 4C require a long spring length to achieve the contact force and compliancy needed for wafer burn-in. Additionally, such probes that use individual wires are too expensive for use in wafer burn-in where many thousands of probes are required for each wafer.
• Further approaches to providing flexible probes involve the use of compliant layers interposed between a test head and a device being tested, such that terminals on the test head are electrically connected to mating contact pads on the device. The electrical connector described in U.S. Pat. No. 3,795,037 by Willem Luttmer utilizes flexible conductors embedded in an elastomer material to make connections between mating pairs of conductive lands that are pressed into contact with the top and bottom surfaces of the electrical connector. Many variations of flexible conductors including slanted wires, conductive filled polymers, plated posts and other conductive means in elastomeric material in order to form compliant interposer layers.[0015]
• The approaches listed above and other attempts have been unsuccessful in providing a high performance probe that allows economical burn-in and speed test of microelectronic devices on a wafer before the wafer is diced into discrete chips.[0016]
SUMMARY OF THE INVENTION
• In accordance with the present invention, a single-sided compliant probe is provided that includes a conductive tip, which is positioned on a supporting substrate in a manner that allows a tip on the probe to move flexibly with respect to the supporting substrate, while in close proximity to adjacent probes in an array. The probe tip moves vertically in response to the force of a mating contact pad as it is mechanically biased against the tip. Mechanical compliance of the probe allows electrical contact to be made reliably between the probe and a corresponding contact pad on a microelectronic device, where the mechanical compliance accommodates variations in height of the contact pad.[0017]
• The present invention is useful for making electrical connection to contact pads on microelectronic devices on an undiced wafer in order to burn-in the devices before they are diced into separate chips. Compliant probes according to the invention allow reliable electrical connections to be made simultaneously to all of the contact pads arrayed on the surface of a wafer so that microelectronic devices on the wafer can be burned-in economically. Mechanical compliance of probes in the fixture accommodates variations in height of the contact pads and in the probe tips such that each probe tip remains in contact with its mating contact pad throughout the temperature cycle of the burn-in process.[0018]
• The present invention also provides an element of an electrical probe card that allows high speed testing of unpackaged microelectronic devices. Small, single-sided compliant probes as taught in this disclosure are used to make temporary connections to corresponding pads on a device in order to apply electrical test signals to that device and to measure electrical signals from that device. The small size of the compliant probe allows high speed electrical signals to be passed to and from the device without losses due to excessive inductance or capacitance associated with wire probes as used in the prior art.[0019]
• Small, compliant probes as taught in this disclosure are used to make reliable electrical connections to contacts on the device, where the contacts are arranged in an area array. Mechanical compliance allows the tip of each probe to maintain electrical contact with a mating contact on the device notwithstanding variations in the height of contacts on the device both at room temperature and at the operating temperature range of the device.[0020]
• The present invention also provides a small socket for connecting integrated circuit chips to electrical circuits for purposes of burn-in, test and operation of the chip. The small size of each probe contact in the socket allows high-speed operation of a chip mounted in the socket. Mechanical compliance of the probes as taught in this disclosure enables reliable electrical connections to be made to a rigid chip with minimal or no packaging. Compliant probes according to the present invention allow construction of small, economical sockets for chip scale packages and for flip-chips.[0021]
• The probe disclosed herein is significantly improved over conventional cantilever probes in that it provides a greater range of compliant motion of the probe tip for any given probe force and probe size. A conventional cantilever probe is limited by the range of motion it provides in response to a given force the elastic limit of the probe material is reached. The maximum mechanical stress in cantilever probes is concentrated on the surface of the cantilever material at the point of flexure. The invention provides a greater range of motion for a given spring material and probe force before it reaches the elastic limit of that material.[0022]
• The invention increases manufacturing efficiency for microelectronic devices by providing test and burn-in functions reliably at the wafer level, while at the same time reducing the size of the test fixture. The mechanically compliant probe provides a large range of motion relative to the size of the probe. This range of motion is important in making connections to a device with contact pads that are not substantially in the same plane. The compliant probe tip moves flexibly to accommodate differences in the height of mating contact pads while maintaining sufficient force of the probe tip on the contact pad to assure reliable electrical contact therebetween.[0023]
• A probe tip is disposed on an elongated thin strip of material that is supported rigidly by a rigid post at one end and slidably by a protrusion disposed at a distance from the first end, wherein the tip is located at a predetermined distance from a center line connecting the centers of the rigid post and the protrusion. The probe tip thus supported is able to move compliantly in a vertical direction by torsional and bending flexure of the thin strip of material.[0024]
• The invention is able to increase manufacturing efficiency for microelectronic devices by performing test and burn-in functions reliably at the wafer level, while at the same time reducing the size of the test fixture.[0025]
• The invention will be better understood by reference to the following detailed description in conjunction with the accompanying drawings.[0026]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows a sectional view of a cantilever probe of the prior art.[0027]
• FIGS. 2A and 2B show cross sectional views of flexible membrane probes of the prior art.[0028]
• FIGS. 3A and 3B show views of a probe fabricated on a silicon wafer of the prior art where FIG. 3A shows a plan top view of the probe and FIG. 3B shows a sectional view of the probe.[0029]
• FIGS. 4A to[0030]4C show flexible post probes of the prior art.
• FIG. 5 shows a view of a single-sided compliant probe of a first embodiment in accordance with the present invention.[0031]
• FIG. 6 shows a view of a single-sided compliant probe of a second embodiment in accordance with the present invention.[0032]
• FIGS. 7A to[0033]7C show an third embodiment of a single-sided compliant probe where FIG. 7A is a top plan view, FIG. 7B is a sectional view of the probe at rest, and FIG. 7C is a sectional view of the probe when acted upon by force F.
• FIG. 8A shows a perspective view the single-sided compliant probe as the probe tip is acted upon by a vertically directed force F.[0034]
• FIG. 8B shows the deflection[0035]6 of the tip of the probe of FIG. 8A as a function of the force F acting on the probe tip.
• FIGS. 9A and 9B show arrays of single-sided compliant probes where FIG. 9A is a top plan view of n interleaved array of probes and FIG. 9B is a plan view of a linear array of probes.[0036]
• FIG. 10 shows a view of a third embodiment of a single-sided compliant probe with a probe tip located over a void in the substrate holding the probe.[0037]
• FIG. 11 shows a view of a fourth embodiment of a single-sided compliant probe with an insulating nipple supporting one end of the probe over a ground plane electrical shield.[0038]
• FIG. 12 shows a probe card for testing chips on a semiconductor wafer.[0039]
• FIGS. 13A to[0040]13F show probe tips for use in single-sided compliant probe structures according to the present invention.
DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION
• For a description of specific embodiments, reference is made to FIG. 5 showing a first embodiment of a single-sided compliant probe. A probe is disclosed that allows reliable electrical connection to be made to contact pads on microelectronic devices such as integrated circuits (ICs), flip-chips, passive devices, and chip scale packages. The probe provides flexible vertical motion of[0041]probe tip81 in response to a force on the tip. Thus, as a contact pad is urged into contact withprobe tip81, mechanical compliance of the structure allows the tip to make contact with the mating contact pad at a force sufficient forprobe tip81 to penetrate an insulating oxide film on the pad. Mechanical compliance of the probe accommodates differences in height of the contact pads in a region of the microelectronic device while providing sufficient force on each probe tip to assure a reliable electrical connection between the tip and the corresponding contact pad. Further, mechanical compliance of the pad is necessary to allow the tip to maintain a connection to the corresponding pad during a test or burn-in cycle where thermal expansion may cause mechanical movement of the probe support with respect to the device.
• [0042]Probe tip81 is supported onlateral extension arm82 that is attached tomain body83 of conductive material. Elongatedflexible strip83 is supported at one end byrigid post85 that is joined tomain body83. Probetip81 moves flexibly in response to a force applied vertically totip81. Vertical movement oftip81 depressesarm82 and torsionally flexesmain body83 which serves as a torsional spring, thereby impressing a restoring force ontip81.Post87 supports the end ofmain body83 so as to reduce cantilever deflection ofmain body83.Post87 rests onsubstrate84 at slidable pivot point89 (FIG. 5) that allows torsional rotation of themain body83.
• In single-sided[0043]compliant probe80 shown in FIG. 5, post85 is supported onsubstrate84 bypad86 which is connected electrically to circuit via88 which is connected in turn to electrical circuitry insubstrate84. By the series of links described above,probe tip81 is connected electrically to circuits insubstrate84 that operate a device that is connected to the probe. In applications such as burn-in of integrated circuits,substrate84 is made of a low expansion material in order to achieve dimensional stability over a wide temperature range such as those used in burn-in, where temperature cycles may go from 25° C. to 150° C. or greater.
• For operation at high frequencies, the electrical links from[0044]probe tip81 to viacontact88 may be arranged to reduce the inductance of the connection to probetip81. The inductive loop may be minimized by locating via88 underprobe tip81. While viacontact88 cannot always be so ideally located, the distance betweenprobe tip81 and viacontact88 should be small in those applications that require high frequency operation.
• FIG. 6 shows a[0045]second embodiment90 of a single-sided compliant probe whereconductive arm92 is oriented at an obtuse angle with respect tomain body93.Main body93 is rigidly attached toelongated post95, which is supported bypad96 onrigid substrate94. Theelongated post95 is oriented at an obtuse angle with respect tomain body93. The obtuse angles ofpost95 andarm92 allow several probes of this design to be assembled adjacently in closely spaced arrays. Electrical connection to tip91 is made througharm92, tomain body93, to post95 to pad96, and through via98 to electrical circuits insubstrate94.
• As seen in FIG. 6, pivot[0046]post97 supportsmain body93 abovesubstrate94 atslidable pivot99 so as to allow torsional rotation ofmain body93. Probetip91 is supported onarm92 such that the center ofprobe tip91 is located at a distance from an imaginary line R-R′ betweenrigid post95 and pivotpost97. A vertical force onprobe tip91 produces a torsional flexure ofmain body93 about an axis represented by line R-R′.Main body93 acts as a torsional spring which produces a counter force acting to oppose force ontip91.
• FIG. 7A shows a plan view from above of a[0047]third embodiment100 of the single sided compliant probe. Flexibleelongated strip103 is made of a sheet of metal shaped to include alateral extension102 at the end ofstrip103. The electrically conductive material ofstrip103 is chosen to exhibit high yield strength in order to act as a torsional spring. Metals chosen from the group consisting of beryllium-copper alloys, tungsten, cupro-nickel, molybdenum, nickel, nickel-titanium, nickel-tungsten, stainless steel, titanium, and alloys thereof are suitable for the torsional spring. One suitable metal is beryllium-copper alloy ASTM Spec. No. B534, with yield strength of 550 mega-Pascals. Another suitable metal is titanium alloy Ti, 8 Al, 1 Mo, 1 V, with yield strength of 910 mega-Pascals.
• [0048]Probe tip101 shown in FIG. 7A is supported onextension arm102. The action ofarm102 andprobe tip101 is shown in sectional views of FIGS. 7B and 7C. A force F applied to probetip101 exerts a torque onstrip103, twisting thestrip103 betweenpost105 andslidable pivot107 and allowingarm102 to depress towardsubstrate104. As seen in the sectional view in FIG. 7C, the vertical motion ofprobe tip101 is due to the action of a torsional bending ofstrip103.
• [0049]Probe tip101 is a pyramid formed by replication of an etch pit formed in a (100) silicon surface by well-known processes. The tip angle of 54.75° is determined by the (111) crystallographic planes in silicon. The material of the tip is tungsten-chromium, which forms a sharp, hard tip that is able to break through aluminum oxide layers on aluminum contact pads typically used on semiconductor IC devices. Materials suitable for making hard probe tips is selected from a group consisting of molybdenum, chromium, nickel, osmium, Paliney 7, rhodium, rhenium, titanium, tungsten, and alloys thereof.
• (Fabrication of sharp probe tips by replication of etch pits in silicon is known in the field of electrical contacts and is described in a publication in 1973 by D. A. Kiewit in Reviews of Scientific Instruments, Vol. 44, pages 1741-1742. Kiewit describes formation of probe tips that are made by replication of etch pits in silicon by depositing nickel-boron alloy into the pit, and then removing the silicon matrix material to expose the pyramid. Kiewit formed pyramidal etch pits in silicon (100) surfaces by treating the surface with boiling hydrazine hydrate.)[0050]
• [0051]Strip103 is supported abovesubstrate104 by apost105 that is rigidly joined tocontact pad106 on thesubstrate104.Post105 is formed of an electrodeposited metal, preferably chosen from the group including hard copper, nickel, cupro-nickel alloys, and hard gold. Electrical connection ofprobe tip101 to circuits for testing integrated circuits is made by conduction througharm102,strip103,post105,contact pad106, and via108. The electrical circuit from via108 to probetip101 is configured to form as small a loop as possible in order to reduce inductance and thereby allow operation at the highest frequencies or data rates.
• FIGS. 8A and 8B illustrate in greater detail the operation of the single-ended compliant probe. In this configuration a[0052]probe tip111 is supported bylateral extension arm112 that is configured at a right angle with respect tomain body113. The main body is supported byrigid post115 and bypivot post117.Pivot post117 is rigidly attached tomain body113, and is supported onsubstrate114 by a slidingcontact119 that allows the post to pivot with respect to the substrate.
• As seen in FIG. 8A, a force F depresses[0053]probe tip111 through a deflection of6 in the vertical direction.Extension arm112 acts as a moment arm that transmits torque tomain body113. The main body is a torsional spring that twists about its axis in response to the torque fromextension arm112.Pivot post117 supportsmain body113 such so as to minimize any cantilever deflection towardsubstrate114, while allowing the main body to twist freely about its axis. The main body is a torsional spring that allows compliant motion oftip111 in response to a force F.
• The total deflection δ of[0054]tip111 shown in FIG. 8B is the sum motions due to twisting of themain body113 and due to cantilever bending ofextension arm112. For this second embodiment, the deflection due to cantilever bending ofextension arm112 is small compared to the deflection due to twisting ofmain body113. FIG. 8B shows the total deflection δ in microns caused by a force F in grams acting vertically onprobe tip111. For this study,main body113 is made of tungsten with a thickness of 50 microns, a width of 62 microns, and a length of 1400 microns.Arm112 is 250 microns long from the centerline ofstrip113 to probetip111, as measured in the plane of the strip.
• The single-sided compliant probe of this invention allows individual probes to be grouped in closely spaced arrays. Several arrays of probes shown in FIGS. 9A and 9B illustrate the invention as adapted to probe closely spaced rows of contact pads.[0055]
• The probe design of FIG. 9A shows an[0056]array120 of probes each with amain body123, anextension arm122 at an angle to the axis of themain body123, and anelongated post125 also at an angle to the axis of themain body123. Eachextension arm122 has aprobe tip121 on the top of the end distant from themain body123. Eachmain body123 is supported by apivot post127 located away from therigid post support125.
• [0057]Array120 of FIG. 9A comprises a cluster of probes arranged in a column on the left side of thearray120, and a similar cluster of probes arranged in a column on the right side of thearray120. The tips on the probes of the column on the right are interleaved with the tips on the probes of the column on the left, forming a row of closely spaced probe tips.
• The probe design of FIG. 9B shows an[0058]array130 of probes, each with amain body133, amoment arm132 at an oblique angle to the axis of themain body133, and anelongated post135 also at an oblique angle to the axis of themain body133. Aprobe tip131 is positioned at the end of eachmoment arm132 distant from themain body133. Eachmain body133 is supported by apivot post137 located at a distance away from therigid post support135.
• [0059]Array130 of FIG. 9B comprises a nested column of probes. The oblique angles ofmoment arm132 and ofrigid post135 allow a close spacing of the probes, one to another, while maintaining a minimum spacing between adjacent probes. The tips on the probes of the column are arrayed in a row to match the contact pads on the chip to be tested.
• FIGS. 10 and 11 show additional embodiments of the single-sided compliant probe where a support pivot is affixed to the substrate rather than to the main body of the probe.[0060]
• A[0061]third embodiment140 is shown in FIG. 10 whereinprobe tip141 is disposed onextension arm142 that lies abovevoid152 insubstrate144. In response to an applied force,extension arm142 andprobe tip141 deflect downward intovoid152 without interfering withsubstrate144. Themain body143 rests at aslideable support149 on aridge147 onsubstrate144 such thatmain body143 is free to twist about its axis in response to torque caused by force onprobe tip141.
• Electrical connection to probe[0062]tip141 is made throughextension arm142 to themain body143, which is joined to post145 that rests oncontact pads146 which in turn is connected to circuits insubstrate144 through via148.
• FIG. 11 shows a[0063]fourth embodiment160 of the single-sided compliant probe, which incorporates a ground plane shield.Protrusion172 supportsmain body163 of the probe onslidable support169 such thatmain body163 is free to twist about its axis by pivoting onslidable support169.Slidable support169 is located near the end of the main body opposite the end supported byrigid post165 so as to limit downward deflection ofmain body163 towardsubstrate164. Inembodiment160,protrusion172 is formed from silica to insulate the conductivemain body163 fromground plane174 located on the surface ofsubstrate164 undermain body163.
• Electrical connection to probe[0064]tip161 is throughextension arm162 tomain body163, in turn connected torigid post165 oncontact pad166.Contact pad166 is connected to circuits insubstrate164 by via168. Theground layer174 underliesprobe tip161 and shields the probe electrically in order to achieve higher performance.
• A wafer probe shown in FIG. 12 provides a demountable means for testing and burning-in semiconductor chips on a wafer.[0065]Array180 of probes, arranged on the surface ofsubstrate182, is configured to be in alignment with contact pads on the chips to be tested. Eachprobe181 is electrically connected byconductive traces186 to circuit means187 for testing microelectronic devices. Electrical signals suitable for operating semiconductor chips are directed to the socket by interconnection means183 from electronic test means184.Cable185 connects the electronic test means184 to the system for burn-in, test or operation of the devices under test.
• Probe tips shown in FIGS. 13A to[0066]13F are configured for specific applications in test and burn-in microelectronic devices such as semiconductor chips. The designs shown in FIGS. 13A to13F are representative of probe tips that can be used to make electrical connection to contact pads on microelectronic devices of various types.
• The probe tip shown in FIG. 13A is preferred for probing aluminum bond pads on integrated circuits.[0067]Apex273 is suited to breaking through an oxide layer on aluminum bond pads.Pyramid272 is formed by replication of an etch pit in a (100) silicon surface.Pyramid272 is supported onsheet spring271.Apex273 ofpyramid272 is defined with an included angle of 54.75° between opposite faces. A hard material is used forprobe tip272, where the material is preferably selected from the group consisting of molybdenum, nickel, osmium, Paliney 7, rhodium, rhenium, titanium, tungsten, and their alloys. In probing soft contacts, materials such as osmium, rhodium, and tungsten are preferred because they react slowly with solders and other soft materials.
• The probe tip shown in FIG. 13B is suited for contacting noble metal contact pads.[0068]Thin disk277 is supported onmetal post276 disposed onsheet spring275.Post276 is undercut by chemical etching to expose edges ofdisk277.Thin disk277 is made of an inert metal preferably selected from the group consisting of gold, Paliney 7, Platinum, Rhodium, and their alloys.
• The probe tip shown in FIG. 13C is suited to contacting solder and other soft materials.[0069]Rounded metal tip281 is supported onmetal post282 that is disposed onsheet spring280.Rounded metal tip281 can be shaped by flash laser melting a high temperature material to reflow into the shape of a spherical section. Materials suitable forrounded metal tip281 include nickel, platinum, rhodium, cupro-nickel alloys, beryllium-copper alloys, and Paliney 7.
• The probe tip shown in FIG. 13D is suited to contacting small contact pads and pads that are spaced closely together.[0070]Probe tip287 withtop edge286 is disposed on the top surface ofsheet spring285.Probe tip287 can be formed by plating the edge of a sacrificial material and then removing that material to leave a thin sheet ofmetal287 projecting vertically fromsheet spring285.
• The probe tip shown in FIG. 13E is suited for making contact to oxidized contact pads, where a wiping motion is used to break through the oxide layer.[0071]Metal fins291 are oriented in the direction of wipe so as to slide along the contact pad and to break through the oxide layer.Metal fins291 are arrayed on the top ofconductive pedestal292, which rests onprobe structure290. The metal fins are fabricated by metal coating the vertical edges of grooves in resist material, and then removing the resist to leavemetal fins291 standing on edge.
• The probe tip shown in FIG. 13F is suited to contacting small contact pads.[0072]Cylindrical post297 has topflat surface296 that is oriented at an oblique angle with respect to the top surface ofprobe structure295 so as to form cuttingedge298 with an acute included angle. When actuated by a wiping motion, cuttingedge298 removes oxides and other contaminants from the surface of contact pads being tested.
• Although several specific embodiments of the invention have been described, numerous modifications and alternatives thereto would be apparent to one having ordinary skill in the art without departing from the spirit and scope of the invention. Therefore, it is not intended that this invention be limited, except as indicated by the appended claims.[0073]

Claims (10)

1. A probe tip on an arm extending from a support means for making electrical connection to a contact pad on a microelectronic device, said probe tip comprising:

an electrically conductive fin structure with a base disposed on said arm for engaging one of said contact pads, said conductive fin structure comprising at least one planar conductive fin having an edge on said arm and a blade on a second edge opposing said first edge, said blade being oriented to scrape along its axis across said contact pad in a plane of motion of said probe tip, wherein a displacement of said fin structure by said contact pad causes said blade to scrape along said axis across said contact pad.

2-12. (Canceled).

13. The probe tip ofclaim 1, wherein said tip structure comprises at least one platelet oriented in said plane of motion of said probe tip and which is parallel to direction of slidable motion.

14-19. (Canceled).

20. A probe for making electrical connections to contact pads on a microelectronic device, said probe comprising:

(a) a rigid substrate;

(b) a strip of electrically conductive material with a first end and a second end, said strip disposed above said rigid substrate and acting as a spring;

(c) a rigid support at said first end

(d) an arm of said strip extending from said second end in a direction laterally to said long axis between said first end of said strip and said second end of said strip and being generally parallel to said rigid substrate;

(e) an electrically conductive tip disposed on a distal end of said arm for engaging one of said contact pads, said conductive tip comprising at least one planar conductive fin having an edge on a top surface of said distal end and a blade on a second edge opposing said first edge, said fin being oriented in a direction of wipe of said probe tip across a corresponding said contact pad;

(f) whereby a mechanical force on said conductive tip toward said rigid substrate is operative to cause flexure of said strip such that deflection of said tip scrapes across said contact pad along said second edge.

21. (Canceled).

22. (Canceled).

23. The probe tip ofclaim 1 wherein said at least one thin conductive fin is at least two metal fins oriented in parallel.

24. A probe tip for making electrical contact to a microelectronic device, said probe tip comprising:

at least two conductive metal fins oriented in parallel and each having an edge on a top surface of a distal end of an arm and a blade on a second edge opposing said first edge, said fins being oriented in a direction of wipe of said probe tip across a corresponding contact pad of said microelectronic device, whereby a mechanical force on said blade toward said rigid substrate is operative to cause deflection of said arm and said fins to scrape across said contact pad along each said second edge.

25. The probe tip according toclaim 23 wherein said fins are spaced more closely together than separation between said first edges and said second edges of said fins for making electrical contact.

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