KR100340754B1 - Connector apparatus - Google Patents

Abstract

A mechanically flexible connector is disclosed that provides reliable electrical connection with contact pads on microelectronic devices. The connector can be used for burn-in of integrated circuits at the wafer level. It can also be used for probe cards and flip chip sockets to test integrated circuits for other applications. The configuration of the connector includes a probe with a tip 81 protruding over the extended spring 83 of the membrane. The thin film spring is supported over the substrate 89 by the posts 85 to allow the probe tip to move freely in the vertical direction by the contact force acting on the probe tip. The bending of the probe tip is flexibly limited by bending and unfolding of the thin film spring. The mechanical flexibility of the tip allows the pads of the integrated circuit and the probe array to contact where the pads are not strictly planar.

Description

Connector device {CONNECTOR APPARATUS}

Microelectronic devices undergo a series of inspections during the manufacturing process to verify their functionality and reliability. The inspection process generally includes a wafer probe inspection, which examines the operation of each chip before cutting and packaging the microelectronic chip from the wafer. Probe cards assembled from long cantilever wires are used to inspect one or multiple chips simultaneously at the wafer level.

In general, less than 100% yield is achieved because not all chips on the wafer are found to be good at wafer probe inspection. The wafer is cut into individual chips, and the good chips are assembled and packaged. To break the defective device, the packaged device is mounted in a socket on a burn-in substrate and electrically operated at a temperature of 125-150 ° C. for a burn-in period of 8 to 72 hours to undergo a dynamic burn-in process. Burn-in inspections facilitate failure mechanisms, leading to early failure and failure of the device, and allow these defective devices to be screened out by functional electrical testing before commercial use.

A full functional check is performed on the packaged device, and the packaged device is operated at various operating speeds to classify each device by its maximum operating speed. Classifying and inspecting the packaged devices also allows the removal of devices that are broken during the burn-in process. Burn-in and inspection of the packaged device is performed using sockets specially designed for burn-in conditions and high-speed inspection respectively. Conventional manufacturing processes are costly and time consuming because they repeatedly process and inspect each discrete device in a series of long steps, and this series of steps takes several weeks to build the total fabrication time for the device. Add by degree.

Significant advances in manufacturing cost and time have been made by burning and inspecting the wafer before it is cut into individual devices. In addition, manufacturing costs and time can be further reduced by fabricating each device on the wafer in chip-sized packaging before the wafer is cut into individual devices. To take advantage of the simplification and reduction of the process of fabricating microelectronic devices, the semiconductor industry has put considerable effort into developing wafer-level packaging, burn-in and inspection methods. In order to achieve these advantages, it is necessary to provide means for burn-in and speed inspection before the inspection chip is cut into each separate device from the wafer.

Conventional cantilever wire probes are not suitable for burn-in and speed inspection of devices on a wafer. Despite the need to burn in all the devices on the wafer at the same time, the cantilever wire probe is too long and bulky to contact all the devices on the wafer at the same time. Moreover, long cantilever wire probes are not suitable for the functional inspection of high speed devices because the length of the wires constituting the probe is long and arranged in parallel to have high inductance and mutual inductance.

Small, high-performance probes that can be produced at low cost are essential for practical use during burn-in and inspection on wafers. In order for the probe to be used for wafer burn-in and inspection, all pads and probes on the device must be in tangible contact while the device is on an uncut wafer. The wafer contact probe must be in electrical contact with a pad on the device that changes the height of the wafer surface. Moreover, the probe must penetrate the oxide layer on the surface of the contact pads for reliable electrical contact with each pad. Many approaches have been attempted to provide a cost-effective and reliable means of contacting the wafer for burn-in and inspection but have not been fully successful.

Many attempts have been made to reliably contact pads of devices on a wafer using small, vertically flexible probes. David R. Robertaard and Robert L. According to the invention presented in US Pat. No. 4,189,825 to Michaels, a cantilever probe for testing an integrated circuit device is provided. In FIG. 1, the cantilever 22 supports the pointed tip 26 over the aluminum contact pad 24 on the chip 23. The flexible member 25 is pushed down to move the tip 26 in contact with the pad 24. The layer of aluminum oxide on pad 24 is dug by pointed tip 26 for electrical contact between tip 26 and the aluminum metal of pad 24. The strength of small cantilever beams is generally insufficient to provide the tip with the force necessary to dig the aluminum oxide layer on the contact pad unless there is an external means of forcing the cantilever. Although cantilever beams of glass, silicon, ceramic material and tungsten have been tried in various configurations, they have not been successful in providing burn-in probes with sufficient force and flexibility.

The flexible membrane probe shown in FIG. 2A is described in a flexible contact probe in the IBM Technical Disclosure Bulletin (October 1972, page 1513). The flexible dielectric film 32 includes a terminal 33 adapted to be in electrical contact with a pad on an integrated circuit. Terminal 33 is connected to inspect the electronic device by a flexible wire 34 attached to contact pad 35. Probes made of flexible polyimide sheets were published by Leslie et al. At the Proceedings of the IEEE International Test Conference (1988). The flexible sheet limits the vertical movement to a certain amount to adjust the height of the bond pads of the integrated circuit on the wafer under test. Thin film probes such as those published by Leslie et al. Provide integrated circuit chip connections for high performance inspection. However, the stability to the size of the thin film is not sufficient so that it cannot contact the pads on the entire wafer throughout the burn-in temperature cycle.

The thin film silicon dioxide film is shown in Figure 2b, Glen J .. US Patent No. 5,225,771 to Liddy. Since the silicon dioxide film 40 has higher stability to size than polyimide, the size stability problem at the time of contact with the pad on the wafer during burn-in inspection could be slightly improved. The probe tip 41 is connected to the circuit trace 45 by a via 44 passing through the film 40, which is connected to an additional layer of circuit element 42 over the dielectric film 43. . The vertical flexibility of the inspection probe on the silicon dioxide film 40 is limited, making the probe array less reliable for use in burn-in of devices on semiconductor wafers.

The fabrication of an array of burn-in probes on a semiconductor wafer is shown in FIGS. 3A and 3B, respectively, in plan and cross-section, as described in US Pat. No. 4,585,991. The probe 51 is a pyramidal shape attached to the semiconductor wafer substrate 52 by an arm 54. Material 53 is removed from semiconductor wafer 52 to mechanically separate probe 51. The probe of FIG. 3A provides limited vertical motion but does not leave the wiring space required on the substrate to connect the probe array and the inspection electronics and is necessary for dynamic burn-in.

One way to provide a flexible probe to the device's contact pads is to connect the test circuit elements to the pad using a flexible wire or post. 4A shows a flexible probe described in US Pat. No. 5,977,787 to Jovi or Das et al. The probe 60 is the same as that disclosed in US Pat. No. 3,806,801, already issued to Ronald Bob as a buckling beam. Probe 60 is suitable for use in burn-in of devices on a wafer. Guides 61 and 62 supporting the probe 60 have the same coefficient of expansion as the wafer being inspected. The probe tip 63 is bent by a small length 60 to provide the correct form in which the beam 60 is deflected. Although the clamp beams are suitable for inspecting each integrated circuit chip, they are too expensive to use for wafer burn-in requiring thousands of contact points. Moreover, the electrical performance of the clamp beam probe is limited because of the length needed to make the proper bend of the beam.

Another approach using a flexible post is shown in FIG. 4B, which is Arnold W. Invention described in US Pat. No. 5,513,430 to Janov and William Dowshire. 4B shows a flexible probe in the form of a post 66 that can bend under the force applied to the probe tip 67. The post 66 is formed while maintaining a certain angle with the substrate 69 in order to bend vertically in accordance with the force applied to the tip 67 while in contact with the contact pad. The post 66 is tapered from the base terminal 68 to the tip 67 to facilitate bending.

Benjamin Y in Figure 4c. Another type of flexible wire and post is shown in US Pat. No. 5,878,486 to Eldridge et al. The probe shown in FIG. 4C includes a probe tip 72 on the spring wire 71, which is bent into a specific shape to facilitate bending. The wire 71 is bonded to the substrate 74 by a general wire bond 73. Probes of the type shown in FIG. 4C require long springs to achieve the contact force and flexibility required for wafer burn-in. Moreover, these probes, which require each wire, are too expensive to use for wafer burn-in requiring thousands of contact points.

Another way of providing a flexible probe is to insert a flexible layer between the test head and the device under test so that the terminals on the test head are electrically connected to the corresponding contact pads of the device. The electrical connector described in US Pat. No. 3,795,037 to Willem Rummer uses a flexible conductor inserted in an elastic material to connect between a pair of conductive lands that are pressed to contact the upper and lower sides of the electrical connector. Various modifications of the flexible conductor include the use of conductive means in the rubber material to form the bent wire, the polymer filled with the conductor, the plated post and the flexible insert layer.

The foregoing schemes and other attempts have not been successful in providing high performance probes that enable economical burn-in and speed inspection of microelectronic devices on a wafer before the wafer is cut into individual devices.

This application is used with reference to the currently pending application content entitled "Flexible Probe Device".

The present invention relates to burn-in and inspection of microelectronic devices, and more particularly to probes for use in socket assemblies suitable for use in connecting integrated circuits in the form of single chips or wafers.

The novel features which can be seen as features of the invention are set forth in the appended claims. Other features and advantages as well as the invention itself may be best understood by the following detailed description with reference to the accompanying drawings.

1 is a cross-sectional view of a cantilever probe of the prior art.

2A and 2B are cross-sectional views of prior art flexible thin film probes.

3A and 3B are plan and cross-sectional views, respectively, of prior art probes fabricated on silicon wafers.

4A-4C illustrate prior art flexible post probes.

5 shows a flexible probe according to the present invention.

6 illustrates another configuration of a flexible probe that includes a ground plane shield.

7A-7C are, respectively, a top view, a cross-sectional view at rest, and a cross-sectional view of the probe when force F acts on one embodiment of the flexible probe.

8A-8D are plan views of different embodiments of probe design for a flexible probe according to the present invention, respectively.

9A-9D illustrate probe tips used in a flexible probe structure in accordance with the present invention.

10 illustrates an embodiment of a flexible probe.

11 illustrates an embodiment of a flexible probe comprising an elastic capsule material.

12A-12C are, respectively, a top view, a cross-sectional view at rest, and a cross-sectional view of the probe when force F acts on one embodiment of the flexible probe.

13A and 13B are plan and cross-sectional views, respectively, of an embodiment of a flexible probe with an integral ground shield.

14 is a cross-sectional view of another embodiment of a flexible probe with an integral ground shield.

15A shows an inspection head device including a flexible probe.

FIG. 15B is a cross-sectional view of the flexible probe of FIG. 15A.

In accordance with the present invention, a compact flexible probe comprising a conductive tip is provided, the conductive tip being positioned on the support surface to flexibly move relative to the support surface. The probe tip is moved vertically by the force generated as the corresponding contact pad is pressed by the tip. The mechanical flexibility of the probe ensures electrical contact between the probe and the corresponding contact pad on the microelectronic device, and the mechanical flexibility controls the height change of the contact pad.

It is an object of the present invention to provide a method and means by which a microelectronic device can be electrically connected with the contact pads of the device on the uncut wafer to burn in before being cut into separate chips. The microelectronic device on the wafer can be economically burned in because the flexible probe according to the invention reliably and electrically connects simultaneously with all the contact pads arranged on the surface of the wafer.

Another object of the present invention is to provide a structure for the burn-in of microelectronic devices on an uncut wafer. The structure is in electrical contact with the contact pads on each device to drive circuit elements that supply the device with the electrical signals required during the high temperature dynamic burn-in. Electrical signals and power are simultaneously supplied to all chips on the wafer. The mechanical flexibility of the probes in the structure adjusts the height of the contact pads and the change in the probe tips so that each probe tip remains in contact with the corresponding contact pad throughout the temperature cycle of the burn-in process.

It is yet another object of the present invention to provide an electrical probe card that enables high speed inspection of unpackaged microelectronic devices. Miniature flexible probes are used to temporarily connect with corresponding pads on the device to apply an electrical test signal to the device and to measure the electrical signal from the device as disclosed herein. Because of the small size of the flexible probe, it is possible to send and receive high-speed electrical signals to the device without loss of excessive inductance or capacitance occurring in the wire probes used in the prior art.

It is a further object of the present invention to provide a method and means for burn-in, inspection and operation of a device when the electrical contacts of the microelectronic device are arranged in a two-dimensional arrangement on the surface of the device. Miniature flexible probes are used to make a reliable electrical connection with the contacts of the device when the contacts are arranged in a two-dimensional arrangement as disclosed herein. Mechanical flexibility allows the tip of each probe to maintain electrical contact with the corresponding contact of the device despite changes in the height of the contact, both at room temperature and the operating temperature range of the device.

Another object of the present invention is to provide a small socket connecting the integrated circuit chip and the electrical circuit for burn-in, inspection and operation of the chip. The small size of the probe contacts in the socket allows for high speed operation of the chip mounted in the socket. The mechanical flexibility of the probe allows for reliable electrical connection to a minimally packaged rigid chip or an unpackaged rigid chip as disclosed herein. The flexible probe according to the invention makes it possible to make small and economical sockets for chip-scale packaging and flip chip.

These and other objects of the present invention can be solved by providing a mechanically flexible electrical probe, wherein the probe tip is disposed between both ends of the extended thin film spring of flexible material. The extended thin film spring is supported over the substrate by posts at both ends of the spring, causing the tip to flexibly move in the vertical direction as the spring material bends and unfolds.

The probe described herein is a significant improvement over conventional probes in that the probe tip moves more flexibly than conventional cantilever probes, given the force applied to the probe and the size of the probe. Conventional cantilever probes have a limited range of motion depending on the constant force exerted by the elastic limit of the probe material. The maximum mechanical stress in the cantilever probe is concentrated on the surface of the cantilever material at the bending point. The present invention allows a greater range of movement with respect to the force exerted on the spring material and the probe before a given spring material reaches the elastic limit.

According to the present invention, the inspection and burn-in functions can be reliably provided at the wafer level, thereby increasing the manufacturing efficiency of the microelectronic device and reducing the size of the inspection structure. Mechanically flexible probes have a large range of motion relative to the size of the probe. This range of movement plays an important role in connecting devices with contact pads that are not substantially coplanar. The flexible probe tip moves flexibly to adjust the difference in height of the corresponding contact pad while maintaining sufficient force on the probe tip on the contact pad to reliably establish electrical contact between the tip and the contact pad.

A first embodiment of a flexible probe in accordance with the principles of the present invention is shown in FIG. Probes are disclosed to enable stable electrical connections with contact pads on microelectronic devices such as integrated circuits (ICs), flip chips, passive devices, and chip scale packaging. The probe allows for smooth vertical movement of the probe tip 81 according to the force acting on the tip. Thus, as the contact pad is pressed to contact the probe tip 81, the mechanical flexibility of this structure allows the probe tip 81 to contact the corresponding contact pad with sufficient force to pass through an insulating oxide film on the contact pad. The mechanical flexibility of the probe adjusts the height difference of the contact pads in the area of the microelectronic device, while applying sufficient force to each probe tip to enable a reliable electrical connection between the tip and the corresponding contact pad. Furthermore, there is also a need for mechanical flexibility of the pads to keep the tip in contact with the corresponding pad during inspection or burn-in cycles, which may result in distortion of the device and probe support due to thermal expansion.

In FIG. 5, the probe tip 81 is supported over an extended thin film spring 83 of conductive material. The thin film spring 83 is supported by the posts 85, and the posts 85 are engaged with the chuck pads 84 at both ends of the extended thin film spring 83. The probe tip 81 can be flexibly moved by the force applied perpendicular to the tip. The vertical movement of the tip 81 causes the thin film spring 83 to bend and unfold flexibly so that a flexible restoring force is applied to the tip 81.

In the flexible probe shown in FIG. 5, the post 85 is supported over the substrate by a terminal 86 that is electrically connected with the circuit trace 87. Circuit trace 87 is in turn connected with electrical circuitry of substrate 89 through via 88. The aforementioned series of connections connects the probe tip 81 with the circuitry of the substrate 89 to operate the device connected to the probe. When used in burn-in or the like, the substrate 89 is made of silicon or low-expansion ceramic material to achieve size stability over a wide temperature range, such as burn-in, with a temperature cycle of 25 ° C. to 150 ° C. or higher.

In order to operate at high frequencies, the electrical connection from the probe tip 81 to the via contact 88 is arranged to minimize the inductance caused by the connection with the probe tip 81. The inductance of the loop can be minimized by placing the via contact 88 substantially below the probe tip 81. Although via 88 may not always ideally be located under the probe tip, the distance between tip 81 and via 88 should be short when high frequency operation is required.

FIG. 6 shows a second embodiment of the flexible probe, wherein the extended thin film spring 93 is shielded from the circuit of the substrate 99 by the ground plane shield 92. Ground plane shield 92 is electrically insulated by dielectric layers 98A and 98B. Dielectric layer 98A is inserted between the top surface of substrate 99 and ground surface 92. Additional dielectric layer 98B is an elastic dielectric material inserted between ground plane 92 and thin film spring 93. The elastic material of the dielectric layer 98B is preferably selected from the group consisting of silicon, silicon fluoride, carbon fluoride and urethane polymers. The elastic dielectric layer 98B insulates the thin film spring 93 from the ground plane 92 while bending the spring 93 vertically.

In FIG. 6, contact pads 94 on each end of elongated thin film spring 93 are engaged with posts 95, which in turn are positioned on pads 96 on substrate 99. The probe tip 91 is electrically connected to the contact pad 94 through the thin film spring 93, the contact pad 94 is coupled with the post 95, the post 95 is located above the terminal 96, Terminal 96 is in turn connected to and electrically connected to the electrical circuit of substrate 99 by circuit trace 97.

As shown in FIG. 6, the probe tip 91 is positioned above the thin film spring 93 but at a predetermined position along the centerline between the posts 95 at both ends of the extended thin film spring 93. The vertical force acting on the probe tip 91 is flexibly opposed to the counter force generated by the elastic bending and unwinding of the thin film spring 93 and the counter force generated by the deformation of the elastic layer 98B.

FIG. 7A is a plan view from above of a first embodiment of the flexible probe of the general type illustrated in FIG. 5; FIG. The extended thin film spring 103 consists of a metal sheet comprising contact pads 104 formed at both ends of the sheet. The metal of the thin film spring 103 is selected to have a high production strength and a moderate elongation to final failure. Preference is given to metals made of molybdenum, cadmium, stainless steel, beryllium-copper, copper-nickel, nickel, titanium and alloys thereof. A suitable metal of this is beryllium-copper alloy ASTM specification number 534 with a production strength of 550 megapascals. Another suitable metal is a titanium alloy with a production strength of 910 megapascals and consisting of Ti, 8 Al, 1 Mo, 1V.

The probe tip 101 shown in FIG. 7A is supported on the thin film spring 103 and is pressed vertically toward the substrate 109 by the vertical force F applied to the probe tip 101. Vertical depression of the probe tip 101 is shown in the cross-sectional views of FIGS. 7B and 7C. The vertical force F acting on the probe tip 101 flexes the thin film spring 103 so that the tip 101 is pressed against the substrate 109. As shown in the cross-sectional view of FIG. 7C, the vertical movement of the probe tip 101 is due to the bending and unfolding of the spring 103.

The probe tip 101 is a pyramid formed by replication of an etch pit formed in the crystal plane 100 of silicon by a known process. A tip angle of 54.75 ° is determined by the crystal plane 111 of silicon forming the slope of the pyramid. The material of the tip 101 is tungsten, which forms a sharp and hard end that can penetrate the aluminum oxide film over the aluminum contact pads commonly used in semiconductor integrated circuit devices. Suitable materials for making rigid probe tips are molybdenum, nickel alloys, osmium, Paliney 7, rhodium, rhenium, titanium, tungsten and their alloys.

It is known in the art to replicate the etch pit of silicon to produce a sharp probe tip. a. Kiwit, in the 1973 publication of Reviews of Scientific Instruments, Vol. 44, pp. 1741-1742. Kiwit describes a probe tip by replicating an etch pit of silicon by depositing a nickel-boron alloy on the pit and then removing the silicon matrix material to expose the pyramid. Kiwit was surface treated with boiling point hydrazine hydroxides to form pyramidal etch pits on the silicon (100) plane.

The thin film spring 103 is supported over the substrate 109 by a post 105, and the post 105 is coupled with the terminal 104 at both ends of the extended thin film spring 103. The post 105 is preferably formed of an electrodeposition metal selected from the group consisting of hardened copper, nickel, copper-nickel alloys or hardened gold. The electrical connection between the probe tip 101 and the circuitry for inspecting the integrated circuit connects the spring 103, the contact pad 104, the post 105, the terminal 106, the circuit trace 107 and the vias 108. By evangelism through The electrical circuit from the via 108 to the probe 101 is configured to form a loop that includes the smallest area possible to reduce inductance so that it can operate at high frequencies or at high data rates.

Some other configurations of the flexible probe are shown in FIGS. 8A-8D. Some configurations facilitate contacting probes with closely located contact pads in a linear array on an integrated circuit. Contact pads on modern integrated circuits are as small as 60 micrometers between centers. In order to contact the closely spaced probe pads, specially designed probes are superimposed in a specially designed arrangement. The probe design shown in FIGS. 8A-8D provides a means for contacting when the contact pads on the integrated circuit device under test are closely spaced arrays.

The flexible probe shown in FIG. 8A allows the probe to overlap in the form of an array of elongated thin film springs oriented at an angle with the axis of the linear array of probe tips 111. This configuration includes a spring having a probe tip 111 disposed between the short portion 113 and the long portion 112 of the spring. The contact pads 114, 116 are located at the ends of the short portion 113 and the long couple 112, respectively. The spring is supported by the post 115 under the short portion 113 and the post 117 under the long portion 112. Posts 115 and 117 with staggered positions allow the probes to be closely spaced from one another.

The flexible probe shown in FIG. 8B includes an extended thin film spring having a short portion 123 terminating at the contact pad 124 and a long portion 122 terminating at the contact pad 126. The probe tip 121 is disposed between the long portion 122 and the short portion 123. Contact pad 126 is supported by post 127, and contact pad 124 is supported by post 125. As shown in Fig. 8B, by arranging a plurality of probes alternately between short and long portions on a line, the probes are in the form of arrays with close spacing suitable for inspecting integrated circuits with small pad spacing. Overlaps.

In FIG. 8C, the flexible probe includes an elongated thin film spring 133 held between two contact pads 134, 136. The probe tip 131 is disposed above the spring 133 at the center point between the contact pads 134, 136 and the posts 135, 137, which are respectively coupled. The elongated posts 135, 137 and the elongated contact pads 134, 136 are oriented at an angle so that the probes overlap in a closely spaced arrangement as shown in FIG. 8C.

The flexible probe shown in FIG. 8D includes an extended thin film spring having a short portion 143 ending at the contact pad 144 and a long portion 142 ending at the contact pad 144. The probe tip 141 is disposed above the spring between the long portion 142 and the short portion 143. Elliptical posts 145, 147 support contact pads 144, 146, respectively, to allow the probes to overlap in a closely spaced arrangement. The spring portions 142, 143 flex and flex when the contact pads on the device are inclined with respect to the probe tip 141.

The probe tips shown in FIGS. 9A-9D are adapted for specific applications in the inspection and burn-in of microelectronic devices. Such probe tips and other tips are known in the industry in the field of integrated circuits. The examples presented herein are representative of the many types of probe tips currently in use. Methods of making such probe tips are also well known to those skilled in the art of making electrical contacts.

The probe tip shown in FIG. 9A is preferred for contacting aluminum bond pads on integrated circuits, with sharp vertices 153 suitable for drilling oxide films of the aluminum bond pads. The pyramid 152 is formed by duplicating etch pits oriented to the silicon crystal plane 110. Pyramid 152 is supported on thin film spring 151. The vertex 153 of the pyramid 152 is sharply formed with an angle of 54.75 ° between the opposing faces of the pyramid. Preferably, a hard material selected from the group consisting of molybdenum, nickel, osmium, parini 7, rhodium, rhenium, titanium, tungsten and alloys thereof is used for the probe tip 152. Osnium, rhodium and tungsten are preferred for use as probes in contact with soft contacts because they react slowly with solder and other soft materials.

The probe tip shown in FIG. 9B is preferred for contacting a noble metal contact pad. The thin film disc 157 is supported on the metal post 156 disposed on the surface of the thin film spring 155. The lower portion of the post 156 is etched by a chemical etching process to expose the edge of the disk 157. The thin film disc 157 is preferably formed of an inert metal selected from the group consisting of gold, parini 7, platinum, rhodium and alloys thereof.

The probe tip shown in FIG. 9C is desirable for contact with solder and other soft materials. The rounded metal tip 161 on the metal post 162 is disposed on the leaf spring 160. The metal tip 161 flash-melts the hot material to reverse the spherical shape into one portion to form a rounded shape. Suitable materials for the rounded metal tip 161 include metals selected from the group consisting of nickel, platinum, rhodium, copper-nickel alloys, beryllium-copper alloys, and parini 7.

The probe tip shown in FIG. 9D is preferred for contacting small area contact pads and pads that are closely spaced from each other. A probe tip 167 with an upper edge 166 is disposed on the upper side of the thin film spring 165. The probe tip 167 is preferably formed by plating the edges with sacrificial material and then removing the sacrificial material so that a thin portion 167 of the metal oriented in the vertical direction remains.

FIG. 10 shows a third embodiment of a flexible probe, in which flexibility is enhanced by corrugation in which the thin film spring 172 is oriented in a direction perpendicular to its longitudinal direction. The one or more pleats allow the spring 172 to bend and straighten more easily, allowing for more flexibility in accordance with the vertical force applied to the probe tip 171. The pleats 173 are formed by duplicating extended etch pits formed in the crystal plane 100 of silicon. Methods for etching extended pits on silicon surfaces are described in (100) and (110) planes of silicon on Ernest Vasus, IEEE Transaction on Electron Devices, ED-25, 10 (1978), page 1184. It is a well-known technique as represented by a paper entitled "Method for producing a novel three-dimensional microstructure by etching anisotropically. The corrugation is made by depositing a metal strip in a direction perpendicular to the longitudinal axis of the etch pit.

In FIG. 10, the terminals 174 on both ends of the extended thin film spring 172 are coupled with the post 175, which supports the spring at a distance above the substrate 179. Post 175 is located on contact pad 176, which is connected to electrical circuitry of substrate 179 by circuit traces 177 and vias 178.

As shown in FIG. 10, the probe tip 171 is positioned above the thin film spring 172 but at a distance from the post 175 at both ends of the extended thin film spring 172. The vertical force acting on the probe tip 171 causes the thin film spring 172 to bend and unfold flexibly, and the flexibility is enhanced by the bending of the pleats 173. The height of the pleats 173 is determined by adjusting its width so as not to contact the top of the device under inspection.

FIG. 11 shows a fourth embodiment of a flexible probe wherein the circuit 187 on the surface of the substrate 189 is protected by an elastic capsule 188. An elastic capsule 188 is inserted between the thin film spring 182 and the upper side of the substrate 189. The capsule 188 resists corrosion and mechanical damage, while allowing the thin film spring 182 to move flexibly as the probe tip 181 is pressed into the corresponding contact pad on the device being inspected.

In the fourth embodiment, the extended thin film spring 182 has one or more corrugations 183 oriented perpendicular to its longitudinal axis. The spring 182 is supported at a height above the substrate 189 by the post 185, and the post 185 is coupled with the terminals 184 on both ends of the extended thin film spring 182. Post 185 is located on contact pad 186, which is connected to electrical circuitry of substrate 189 by circuit trace 187 via via 188.

A configuration to include two pleats 193 in the third embodiment is shown in detail in FIGS. 12A-12C. 12A shows a flexible probe with a probe tip 191 disposed on a thin film spring 192. The spring 192 is a copper-nickel thin film of Monel alloy K-500. The thickness of the thin film spring 192 is between 10 and 75 micrometers, more preferably in the range of 25 to 50 micrometers. The width of the thin film spring 192 is between 20 and 150 micrometers, more preferably between 30 and 75 micrometers. The distance between the center of the post 195 at the first end 194 of the spring 192 and the center of the post 195 at the second end 194 of the spring 192 is approximately 200-1500 micrometers. More preferably the spacing between the centers of the posts is 250 to 750 micrometers.

The reaction that occurs as the normal force F is applied to the probe 191 is illustrated in FIGS. 12B and 12C, which are cross-sectional views of the probe before and after the normal force F acts. As shown in FIG. 12C, the normal force F applied to the probe tip 191 pushes the thin film spring 192 downward toward the substrate 199. The spring 192 is elastically bent and unfolded, thereby generating an opposing force against it as the tip 191 is bent by the vertical force F. Pleat 193 enhances overall flexibility because spring 192 reinforces the flexing and bending of the movement. Specifically, the pleats 193 reduce the axial stress in the spring 193 and significantly relieve the stress caused by the spring 192 unfolding.

The probe tip 191 is connected to an electrical circuit used to operate the device under test. The probe tip 191 is connected by a spring 192, which is supported by a post 195 coupled to the contact pad 194 at both ends. Post 195 is positioned over terminal 196 on the surface of substrate 199. Terminal 196 is in turn connected with circuit trace 197, which is coupled to the electrical circuit at substrate 199 by conductive via 198. Optionally, a ground plane may be inserted between the probe tip 191 and the circuitry of the substrate 199 to shield the tip 191 from signals of adjacent circuit traces of the substrate 199.

13A and 13B illustrate a flexible probe that provides the low inductance needed to fully perform integrated circuit inspection. 13B is a cross-sectional view of the flexible probe, where the probe tip 201 is located on the thin film spring 202. In the spring 202, a return ground path for the signal is formed of the metal layer 212, which is insulated from the spring by a dielectric layer 211 inserted between the spring 202.

The signal at the probe tip 201 and the associated ground return signal are both connected by a shorted electrical path to their respective circuit at the substrate 209. The probe tip 201 is connected with a support post 205 that is coupled with a contact pad on the spring. The post 205 is positioned over the terminal 206 connected with the circuit trace 207, and the circuit trace 207 is in turn connected with the inspection circuit of the substrate 209. The corresponding ground return signal of the electrode 212 is connected with the support post 215. The post 215 is positioned over the terminal 216 connected to the ground trace 217, and the ground trace 217 is again connected to the ground circuit of the substrate 209.

FIG. 14 illustrates another embodiment of a flexible probe having a ground return signal described so far with reference to FIGS. 13A and 13B. The probe of FIG. 14 is mechanically strong because the elongated thin film spring 222 not only has a crease 223 to relieve stress, but also is directly supported by the post 225 at both ends. The probe tip 221 is connected to the inspection circuit of the substrate 229 by a connection through a spring 222, a contact pad 224, a post 225, and a terminal 226 connected to the inspection circuit at the substrate 229. It is. The ground electrode 235 is insulated from the spring 222 by a dielectric film inserted therebetween. The ground return path is a path from ground electrode 235 to post terminal 236 to ground terminal 233 on substrate 229.

Ground electrode 235 is coupled to a separate post 236 attached to ground terminal 233 on substrate 229. The ground electrode 235 is insulated from the spring 222 by a dielectric film 231 inserted between the spring 222 and the spring 222.

15A shows an inspection head device including a flexible probe with a ground return electrode. The inspection head provides a means for inspecting a high performance integrated circuit chip. The high performance electrical contacts connect pads on the chip to drive circuitry 259 connected to the input / output channels of the high speed chip tester. Each probe is connected to a chip inspector's channels S1, S2, S3, S4,... By a circuit trace 258, the circuit trace 258 at terminal 257 on the ceramic substrate 249. It is over.

The inspection head is mounted to a ceramic substrate 249 having mechanical and thermal stability. Each flexible probe includes a probe tip 241 disposed on the thin film spring 242, which is supported by the post 245 at a distance above the surface of the substrate 249. The probe 241 moves flexibly in the vertical direction to adjust the height difference of the contact pads on the chip, while maintaining a secure connection with the contact pads on the chip.

The mechanical operation of the flexible probe of FIG. 15A can be better understood with respect to the cross sectional view of FIG. 15B. The probe tip 241 is located in the thin film spring 242, which includes a pleat 243 that increases the flexibility of the probe. Contact pads 244 on both ends of the elongated thin film spring 242 are engaged with the post 245. Post 245 is disposed at terminal 246 on circuit trace 247, and circuit trace 247 is connected to each circuit trace 258 of substrate 249.

The flexible probe shown in FIG. 15B includes a ground return electrode 255 on top of the spring 242. The ground return electrode 255 is insulated from the spring 242 by the thin film dielectric layer 251 inserted between the spring 242 and the spring return electrode 255. The ground return electrode 255 is connected to the ground terminal 253 by a post 256. This configuration prevents the mechanical stress of the spring 242 from being transmitted to the ground circuit 255.

While a few preferred embodiments of the invention have been described, it will be apparent to those skilled in the art that various changes and substitutions may be made therein without departing from the spirit and scope of the invention.

Claims (18)

A probe for making electrical contact with a contact pad on a microelectronic device, (a) an elongated spring made of a conductive material and having an upper side and a lower side and having a first end and a second end; (b) a rigid substrate having an upper side and a lower side; (c) electrical terminals disposed on an upper side of the substrate; (d) a plurality of conductive elements, each connected to a lower side of the extended spring, each connected to one of the electrical terminals on the upper side of the substrate, such that the extended spring is supported at a distance over the upper side of the substrate; Post; And (e) an electrically conductive tip having a base disposed on an upper side of the extended spring and a protrusion over the upper side of the extended spring A top surface of the conductive tip is temporarily connected to a contact pad on the microelectronic device, including And the conductive tip can be flexibly moved in the vertical direction. The probe of claim 1 wherein said elongated spring is a generally flat spring having a length between at most 150 and 1500 micrometers and a thickness of the thinnest portion between 10 and 75 micrometers. The probe of claim 1 wherein said elongated spring is a metal spring comprising one or more corrugations oriented perpendicular to the longitudinal direction. The probe of claim 1 wherein the conductive material is selected from the group consisting of beryllium-copper, cadmium, copper-nickel, molybdenum, nickel, nickel-titanium, titanium, tungsten and alloys thereof. 5. The method of claim 4, wherein the upper side of the conductive tip is made of a hard metal selected from the group consisting of copper-nickel, nickel, osmium, Paliney 7, platinum, rhenium, rhodium, tungsten and alloys thereof. Probe, characterized in that the loss. The probe of claim 1 wherein the electrical circuit pattern is disposed below the elongated spring and the circuit connected with the electrical circuit pattern is disposed below the electrically conductive tip. The probe of claim 1, wherein the probe tip is a pyramid that replicates pit etched to the surface of single crystal silicon. The probe of claim 1 wherein said probe tip is an electroplated bump. A probe for electrically connecting with a contact pad on a microelectronic device, (a) an extended thin film spring made of a conductive material and having an upper side and a lower side and having a first end and a second end; (b) a rigid substrate having an upper side and a lower side; (c) a plurality of rigid conductive posts connected at least one of the lower side of the first and second ends of the thin film spring to support the thin film spring over a top side of the substrate at a predetermined distance; And (d) an electrically conductive tip protruding from the upper side with a base disposed on the upper side of the thin film spring; Wherein the protruding electrically conductive tip is in contact with the contact pad, And the conductive tip is positioned on the thin film spring at a predetermined distance from each of the support posts so that the conductive tip can move in a vertical direction. The method of claim 9, An elastic material disposed between the lower side of the thin film spring and the upper side of the substrate Probe comprising more. The probe of claim 10 wherein said elastic material is selected from the group consisting of silicone, silicon fluoride, carbon fluoride and urethane polymer. 1. A socket for microelectronic devices having a generally planar surface, the contact pad array disposed on said surface, (a) a substrate having an upper side and a lower side; (b) a plurality of flexible probes disposed in the form of an array on an upper side of the substrate and electrically connected to the contact pads; And (c) circuit means coupled to the flexible probe such that the microelectronic device is operated when the flexible probe is connected to the contact pad. Including; Each of the flexible probes An extended thin film spring of conductive material, the lower side being supported by one or more rigid posts at the first and second ends; And A probe tip arranged to move on a top side of the elongated thin film spring a distance from each of the posts Small electronic device socket, characterized in that it comprises a. 13. The microelectronic socket of claim 12, wherein the substrate is made of a silicon material. 14. The socket of claim 13 wherein the microelectronic device is a plurality of integrated circuits arranged on an uncut silicon wafer. The socket of claim 13, wherein the silicon material is a silicon wafer having a thickness of 100 μm to 500 μm. 13. The microelectronic socket of claim 12, wherein the substrate is made of a ceramic material. 17. The socket of claim 16 wherein the substrate has a metal-ceramic multilayer structure and each probe is connected to circuit means for inspecting and burn-in the microelectronic device. 13. The microelectronic socket as claimed in claim 12, wherein a ground shield is disposed under the thin film spring.