KR100343402B1 - Compliant probe apparatus - Google Patents

Abstract

A mechanically flexible probe electrically connected to a contact pad on a microelectronic element is disclosed. Probes can be used to burn integrated circuits at the wafer level. It can also be used in probe cards and flip chip sockets for inspecting integrated circuits as other applications. The configuration of the probe includes a probe tip 81, and the probe tip is supported on an extension arm 82 protruding sideways from the extended leaf spring 83. The spring is supported on the substrate 89 by a post 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 twisting of the leaf spring. The mechanical flexibility of the tip allows the probe array to contact the pad of the integrated circuit where the pad is not exactly planar.

Description

{COMPLIANT PROBE APPARATUS}

The microelectronic device undergoes a series of inspections during the manufacturing process to verify its functionality and reliability. The inspection process generally includes a wafer probe inspection in which the microelectronic chip is cut from the wafer and inspected to determine the operation of each chip prior to packaging. Probe cards assembled with long cantilever wires are used to inspect one or multiple chips at the wafer level at the same time.

Generally, less than 100% yield is obtained because not all chips on the wafer are found to be good in wafer probe inspection. The wafer is cut into individual chips, and good chips are assembled and packaged. To break the defective device, the packaged device is mounted on a socket on the burn-in substrate and is electrically operated at a temperature of 125-150 DEG C for a burn-in period of 8 to 72 hours to undergo a dynamic burn-in process. The burn-in test facilitates the breakdown mechanism to cause initial breakage and failure of the device, and allows the defective device to be screened by functional electrical inspection prior to commercial use.

A full function test is performed on the packaged device and the packaged device is operated at various operating speeds to classify each device by the maximum operating speed of the device. Classifying and inspecting packaged devices also allows removal of broken devices during burn-in. Burn-in and inspection of the packaged device is performed using specially designed sockets, respectively, to accommodate burn-in conditions and high-speed inspection. Conventional manufacturing processes are costly and time-consuming to repeatedly process and inspect each discrete element through a series of long steps, and this series of steps may require a total production time of several weeks Respectively.

Significant improvements in manufacturing cost and time have been achieved by burning and inspecting wafers before the wafers are cut into individual devices. Further, manufacturing cost and time can be further reduced by manufacturing each element on the wafer into a chip-size packaging before the wafer is cut into individual elements. In order to take advantage of simplifying and reducing the process of fabricating microelectronic devices, the semiconductor industry has made considerable effort to develop wafer-level packaging, burn-in and inspection methods. In order to achieve this advantage, it is necessary to provide means for burn-in and speed inspection before the inspection chip is cut into individual separated elements from the wafer.

Conventional cantilever wire probes are not suitable for burn-in and speed inspection of devices on the wafer. Despite the need to simultaneously burn all the devices on the wafer, the cantilever wire probes are too long and bulky to not simultaneously contact all the devices on the wafer. Furthermore, a long cantilever wire probe is not suitable for functional testing of high-speed devices because the length of the wires constituting the probe is long and parallel to each other and high inherent inductance and mutual inductance are high.

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 a probe to be used for wafer burn-in and inspection, all of the pads on the device and the probe must be in firm contact while the devices are on the uncut wafer. The wafer contact probe must be in electrical contact with a pad on the element that changes the height of the wafer surface. Moreover, in order for the probe to make reliable electrical contact with each pad, the oxide layer on the surface of the contact pad must be drilled. 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.

There have been a number of attempts to reliably contact a pad of a device on a wafer using a small, vertically flexible probe. David Al. Lovelard and Robert El. According to the invention disclosed in U.S. Patent No. 4,189,825 to Michaels, a cantilever probe for inspecting an integrated circuit device is provided. 1, the cantilever 22 supports the tip 26 sharpened over the aluminum contact pad 24 on the chip 23. The flexible member 25 is urged downward to move the tip 26 into contact with the pad 24. The aluminum oxide layer on the pad 24 is dug by the sharpened tip 26 for electrical contact between the tip 26 and the aluminum metal of the pad 24. The strength of a small cantilever beam is generally insufficient to apply the force required to dig an aluminum oxide layer on the contact pad to the tip unless there is an external means of applying force to the cantilever. Although cantilever beams made of glass, silicon, ceramic materials and tungsten have been tried in various configurations, they have not succeeded in providing burn-in probes with sufficient strength and flexibility.

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

The thin-film silicon dioxide film is formed as shown in FIG. U.S. Patent No. 5,225,771 to Lydi. The silicon dioxide film 40 was more stable in size than the polyimide, which could somewhat alleviate the problem of size stability during contact to make contact with pads on the wafer during burn-in testing. The probe tip 41 is connected to the circuit trace 45 by a via 44 passing through the film 40 and the circuit trace is connected to an additional layer of the circuit element 42 above the dielectric film 43 . The vertical flexibility of the inspection probe on the silicon dioxide film 40 is limited so that the probe array is unreliable for use in burning a device on a semiconductor wafer.

An array of burn-in probes on a semiconductor wafer is shown in plan and cross-sectional views, respectively, in FIGS. 3A and 3B, as described in U.S. Patent No. 4,585,991. The probe 51 is of a pyramid type attached to the semiconductor wafer substrate 52 with an arm 54. The material 53 is removed from the semiconductor wafer 52 in order to mechanically separate the probe 51. The probe of Figure 3A provides limited vertical motion but does not leave wiring space necessary for coupling the probe array and the inspection electronics and essential for dynamic burn-in on the substrate.

One way to provide the flexible probe to the contact pads of the device is to connect the test circuit elements to the pads using flexible wires or posts. 4A shows a flexible probe as described in U.S. Patent No. 5,977,787 to Joe Binas et al. The probe 60 is similar to that disclosed in U.S. Patent No. 3,806,801 to Ronald Bob as a buckling beam. The probes 60 are suitable for use in burn-in of the elements on the wafer. The guides 61 and 62 for supporting the probe 60 have the same expansion coefficient as the wafer to be 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 clamping beam is suitable for inspecting each integrated circuit chip, they are too expensive to use for wafer burn-in requiring thousands of contacts. Moreover, the electrical performance of the clamping beam probe is limited due to the length required to create the proper bend of the beam.

Another way of using the flexible posts is shown in Figure 4b, U.S. Patent No. 5,513,430 to Yanov and William Duxerson. 4B shows a flexible probe in the form of a post 66 that can be bent according to the force applied to the probe tip 67. [ The post 66 is formed at an angle with the substrate 69 in order to bend vertically in accordance with the force applied to the tip 67 while contacting the contact pad. The post 66 is of a shape that tapers from the base terminal 68 to the tip 67 to facilitate bending.

Figure 4c shows Benjamin Yen. Another type of flexible wire and post described in U.S. Patent No. 5,878,486 to Eldridge et al. The probe shown in Fig. 4c includes a probe tip 72 on the spring wire 71, and the spring wire 71 is bent into a specific shape to facilitate bending. The wire 71 is bonded to the substrate 74 by a common wire bond 73. The probe of the type shown in Figure 4c requires a long spring to obtain 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 contacts.

Another way of providing a flexible probe is to insert a flexible layer between the test head and the element to be tested so that the terminals on the test head are electrically connected to the corresponding contact pads of the device. The electrical connector disclosed in U.S. Patent No. 3,795,037 to Willem Rootmer uses a flexible conductor inserted in an elastic material to connect between a plurality of pairs of conductive lands being urged such that the upper and lower sides of the electrical connector are in contact. Various modifications to the flexible conductors include the use of conductive means within the rubber material to form a bent wire, a polymer filled with a conductor, a plated post, and a flexible insert layer.

The above-described method and other attempts have not succeeded in providing a high-performance probe that enables economical burn-in and speed inspection of a microelectronic device on a wafer before the wafer is cut into individual devices.

This application is referred to using the present application, the title of which is " contact device ".

FIELD OF THE INVENTION The present invention relates to burn-in and inspection of microelectronic devices, and more particularly to contact assemblies for connecting electrical signals to an integrated circuit during burn-in and inspection of individual chips and the entire wafer.

The novel features which are characteristic of the invention are set forth in the appended claims. The invention itself as well as other features and advantages may best be understood by reference to the following detailed description when taken in conjunction with 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 a flexible thin film probe of the prior art.

3A and 3B are a top view and a cross-sectional view, respectively, of a probe of the prior art fabricated on a silicon wafer.

4A to 4C are views showing a flexible post probe of the prior art.

5 is a view showing a flexible probe according to the present invention.

6 is a view showing another configuration of the flexible probe according to the present invention.

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

8A is a view showing an embodiment of a flexible probe when the force F acts on the probe tip in the vertical direction.

8B is a diagram showing the bending of the probe tip of Fig. 8A as a function of the force applied to the probe tip.

Figs. 9A to 9C are respectively a plan view of an embodiment of a flexible probe, a cross-sectional view at rest, and a cross-sectional view of the probe when the force F is acting.

10 is a view showing an embodiment of a flexible probe and its connection circuit.

11 is a view showing an embodiment of a flexible probe having a ground plane.

Figs. 12A to 12C are a plan view of one embodiment of the flexible probe, a cross-sectional view at rest, and a cross-sectional view of the probe when the force F is acting.

13A to 13C are plan views showing other configurations of the flexible probe according to the present invention.

14A to 14C are plan views showing other configurations of the flexible probe according to the present invention.

15A shows a contact-probe head for wafer-level polishing of a device having a two-dimensional array contact.

Fig. 15B is a plan view showing a part of the contact probe head for the element having the two-dimensional array contact portion of Fig. 15A.

16A is a diagram showing a probe card for wafer level inspection of a device having a two-dimensional array contact portion.

FIG. 16B is a plan view showing a part of the probe card for a device having the two-dimensional array contact portion of FIG. 16A. FIG.

17A is a view showing a socket for operating a micro-device having a two-dimensional array contact portion.

Fig. 17B is a plan view showing a part of the socket for a device having the two-dimensional array contact portion of Fig. 17A. Fig.

18A to 18D are diagrams showing probe tips used in the flexible probe structure according to the present invention.

According to the present invention, there is provided a miniature flexible probe comprising a conductive tip, wherein the conductive tip is positioned on the support surface for flexible movement relative to the support surface. The probe tip moves vertically by the force generated as the corresponding contact pad is pressed by the tip. The mechanical flexibility of the probe ensures reliable electrical contact between the probe and the corresponding contact pad on the microelectronic element, and the mechanical flexibility adjusts the height variation of the contact pad.

It is an object of the present invention to provide a method and means for electrically connecting to a contact pad of a device on a wafer that has not been cut in order to burn-in the microelectronic device before it is cut into a separate chip. Since the flexible probe according to the present invention reliably electrically connects simultaneously with all the contact pads arranged on the surface of the wafer, the microelectronic element on the wafer can be economically burned.

It is another object of the present invention to provide a structure for burn-in of a microelectronic device on a not-cut wafer. The structure is in electrical contact with the contact pads on each element to drive circuit elements that supply the necessary electrical signals to the device during dynamic temperature burning at high temperatures. The electrical signals and power are supplied simultaneously to all the chips on the wafer. The mechanical flexibility of the probes in the structure adjusts the height of the contact pads and the variation of the probe tips so that each probe tip remains in contact with the corresponding contact pads throughout the temperature cycle of the burn-in process.

It is still another object of the present invention to provide an electric probe card which enables high-speed inspection of an unpackaged microelectronic device. The miniature flexible probe is used to temporarily connect with a corresponding pad on the element to apply an electrical inspection signal to the element and to measure an electrical signal from the element as disclosed herein. Because of the small size of the flexible probe, high-speed electrical signals can be sent to or received from the device without excessive inductance or capacitance losses 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 burning, inspecting and operating an element when the electrical contacts of the microelectronic element are arranged in a two-dimensional array on the element surface. The miniature flexible probes are used to provide a reliable electrical connection with the contacts of the device when the contacts are arranged in a two-dimensional array as disclosed herein. The mechanical flexibility allows the tips of each probe to maintain electrical contact with the corresponding contacts of the device, despite variations in the height of the contacts at both ambient temperature and device operating temperature range.

It is another object of the present invention to provide a small socket for connecting an integrated circuit chip and an electric circuit for burn-in, inspection and operation of the chip. Since the size of the probe contact portion in the socket is small, high-speed operation of the chip mounted in the socket becomes possible. The mechanical flexibility of the probes allows a reliable electrical connection to a minimally packaged rigid chip or an unpackaged rigid chip as disclosed herein. The flexible probe according to the present invention makes it possible to produce a small and economical socket for chip scale packaging and flip chips.

The probe described herein is significantly improved over conventional probes in that the range of movement of the probe tip is greater than that of a conventional cantilever probe when the force applied to the probe and the size of the probe are defined. Conventional cantilever probes have a limited range of movement depending on the constant force of 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 inflection point. The present invention can make the range of motion larger for a spring material and for a force applied to the probe before the given spring material reaches the elastic limit.

The present invention can reliably provide inspection and burn-in functions at the wafer level, thereby improving the manufacturing efficiency of the microelectronic device and reducing the size of the inspection structure. A mechanically flexible probe has a larger range of motion than a probe. This range of motion plays an important role in connecting devices with contact pads that are not substantially coplanar. The flexible probe tip flexibly moves 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 provide electrical contact between the tip and the contact pad.

These and other objects of the invention can be satisfied by providing mechanically flexible electrical probes. The probe tip is located on a strip of elongated thin film supported at both ends and is located a predetermined distance from a centerline connecting the centers of the supports at both ends of the strip.

The present invention can reliably perform inspection and burn-in functions at the wafer level, thereby increasing the manufacturing efficiency of the microelectronic device and reducing the size of the inspection structure.

A first embodiment of a flexible probe according to the principles of the present invention is shown in Fig. Probes are disclosed for making stable electrical connections with contact pads on microelectronic devices such as integrated circuits (ICs), flip chips, passive devices, and chip scale packaging. The probe enables flexible vertical movement of the probe tip 81 according to the force acting on the tip. Thus, as the contact pad is urged into contact with the probe tip 81, the mechanical flexibility of the contact allows the probe tip 81 to contact the corresponding contact pad with sufficient force to pass through the insulating oxide film on the contact pad. The mechanical flexibility of the probe allows a reliable electrical connection between the tip and the corresponding contact pad by applying sufficient force to each probe tip while adjusting the height difference of the contact pads in the area of the microelectronic element. Moreover, the mechanical flexibility of the pad is also required so that the tip can maintain contact with the corresponding pad during a test or burn-in cycle, where distortion of the element and probe support may occur due to thermal expansion.

In Figure 5, the probe tip 81 is attached to an elongated flexible strip 83 of conductive material and is supported on a side extension arm 82 of conductive material. The elongated flexible strip 83 is supported at both ends by posts 85 and the posts 85 are engaged with the terminals 84 on the extended strips 83. The probe tip 81 can move flexibly by the force applied perpendicular to the tip. The vertical movement of the tip 81 causes the resilient force to be applied to the tip 81 by pressing the arm 82 and twisting the strip 83.

In the flexible probe shown in FIG. 5, the posts 85 are supported on the substrate by a terminal 86 electrically connected to the circuit trace 87. The circuit traces 87 are again connected to the electrical circuitry of the substrate 89 via vias 88. By the above-described series of connections, the probe tip 81 is operable with the circuit of the substrate 89 and with the element connected to the probe. When used in burn-in, the substrate 89 is made of a silicon or low expansion ceramic material to achieve size stability over a wide temperature range, such as a burn-in temperature cycle of 25 ° C to 150 ° C or higher.

Electrical connection from the probe tip 81 to the via contact 88 is arranged to minimize the inductance due to connection with the probe tip 81 to operate at high frequencies. The inductance of the loop can be minimized by placing the via contact 88 substantially below the probe tip 81. [ The distance between the tip 81 and the via 88 should be short in applications where high frequency operation is required, although the vias 88 can not always ideally be positioned below the probe tips.

Figure 6 shows a second embodiment of a flexible probe wherein the conductive arm 82 of Figure 5 has been replaced with a curved or V-shaped portion 92 of the elongated lamina 93 of Figure 6. The terminals 94 at both ends of the extended laminate 93 are joined to the posts 95 and the posts 95 are again located above the pads 96 on the substrate 99. The probe tip 91 is electrically connected to the contact pad 94 through the foil 93 and the contact pad 94 is coupled to the post 95 and the post is positioned over the terminal 96, Is again connected to the electrical circuitry of the substrate by the circuit trace (97).

6, the probe tip 91 is supported on the curved portion 92 of the thin plate 93 so that the center of the probe tip 91 is located between the posts 95 at both ends of the thin plate 93 Is located a predetermined distance from the imaginary line (100). The initial normal force acting on the probe tip 91 generates a torque about an axis indicated by the imaginary line 100. The torque results in a deformation that causes the elongated thin plate 93 to beat, and this deformation generates a counter force against the initial normal force applied to the tip 91. [

FIG. 7A is a plan view of the flexible probe of the first embodiment illustrated in FIG. 6, viewed from above. The elongated strip 103 of flexibility is comprised of a metal sheet having a shape such that it includes a contact pad 104 at both ends of the strip 103 and a side extension 102 formed at a central point of the strip 103. The electrically conductive material of the strip 103 is chosen to have a high production strength and a suitable elongation to final breakage. Such metals are preferably selected from the group consisting of beryllium-copper alloys, columbium, copper-nickel, molybdenum, nickel, nickel-titanium, stainless steel, titanium and alloys thereof. A suitable duplex metal is beryllium-copper alloy ASTM specification number 534 with a production strength of 550 megapascals. Another suitable metal is a titanium alloy having a production strength of 910 mega pascals and consisting of Ti, 8 Al, 1 Mo, and 1 V.

The probe tip 101 shown in Fig. 7A is supported on the extension arm 102 and is vertically pressed toward the substrate 109 by the normal force F applied to the probe tip 101. Fig. The vertical depression of the arm 102 and the probe tip 101 is shown in the cross-sectional views of Figures 7b and 7c. The normal force F acting on the probe tip 101 applies a torque to the strip 103 causing the strip to twist and cause the arm 102 to be pushed towards the substrate 109. 7C, the vertical movement of the probe tip 101 is due to the action of both the warp and twist of the strip 103. As shown in Fig.

The probe tip 101 is a pyramid formed by replication of an etched pit formed on the crystal face 100 of silicon by a known process. The tip angle 54.75 DEG is determined by the crystal plane 111 of the silicon. The material of the tip 101 is tungsten, which forms sharp and hard endpoints and can pass through the aluminum oxide film on the aluminum contact pad, which is typically used in semiconductor integrated circuit devices. Suitable materials for making solid probe tips are molybdenum, nickel alloys, osmium, Paliney 7, rhodium, rhenium, titanium, tungsten and alloys thereof.

Cloning etch pits of silicon to produce sharp probe tips is well known in the art, a. Kwiat, 1973, Reviews of Scientific Instruments, vol. 44, pp. 1741-1742. Kiwitt describes depositing a nickel-boron alloy on a pit, then removing the silicon matrix material to expose the pyramid to replicate the etched pit of silicon to make the probe tip. Kewate was surface treated with hydrazine hydroxide at boiling point to form pyramidal etch pits on the silicon (100) surface.

The strip 103 is supported on the substrate 109 by the posts 105 and the posts 105 are engaged with the contact pads 104 at both ends of the extended strip 103. The posts 105 are preferably formed of electrodeposited metal selected from the group consisting of cured copper, nickel, copper-nickel alloys or hardened gold. The electrical connection of the probe tip 101 with the circuit for inspecting the integrated circuit can be accomplished by providing an electrical connection between the probe tip 101 and the circuit for inspecting the integrated circuit, including the arm 102, the strip 103, the contact pad 104, the post 105, the terminal 106, By conduction through the via 108. The electrical circuit from the via 108 to the probe 101 is configured to reduce the inductance to form the smallest possible loop so that it can operate at high frequencies or at high data rates.

8A and 8B illustrate in detail the construction of a preferred embodiment in which the probe tip 111 is supported by a side extension arm 112 on a thin strip of material 113 and a strip 113 Are supported by two support posts 115. The force F bends the tip 111 in the vertical direction by? _T.

As shown in Fig. 8B, the total degree of bowing δ _T of the tip 111 is the sum of the components of the beam itself bent and the twisted component δ _D. 8B is a graph showing the total warpage? _T (in micrometers) generated by a force F (in grams) applied in a direction perpendicular to the probe tip 111. Fig. In this experiment, the strip 113 is made of molybdenum with a thickness of 25 micrometers, a width of 25 micrometers, and a length of 200 micrometers. The arm 112 is 100 micrometers long from the centerline of the strip 113 to the probe tip when measured in the strip plane.

9A is a view showing in detail a second embodiment of the flexible probe. The probe tip 121 is supported at the V-shaped extension 122 of the elongated thin plate 123. The extension portion 122 supports the tip 121 at a position on one side of the hypothetical line connecting the centers of the posts that support both ends of the extended foil 123. The extension portion 122 has a greater thickness than the body of the extended thin plate 123 to prevent the extension portion from being twisted as the force F is applied.

The probe tip 121 is inclined in the vertical direction toward the substrate 129 by the normal force F acting on the tip 121. [ The extension of the extension portion 122 and the probe tip 121 is shown in the sectional views of Figs. 9B and 9C. The normal force F acting on the probe tip 121 causes the strip 123 to be torqued to twist the strip 123 and cause the extension 122 to push towards the substrate 129. As shown in the sectional view of FIG. 9C, the vertical movement of the probe tip 121 is due to both beam tilting and torsional deformation of the extended thin plate 123.

The thin plate 123 is supported by the posts 125 on the substrate 129 and the posts 125 are coupled to the contact pads 124 at both ends of the thin plate 123. Post 125 is a rigid metal post. The electrical connection of the probe tip 121 and the test circuit is accomplished by the electrical connection of the arm 122, the strip 123, the contact pad 124, the post 125, the contact pad 126, the circuit trace 127 and the via 128, Lt; / RTI > The electrical circuit from the via 128 to the probe 121 is configured to reduce the inductance to form the smallest loop possible to operate at high frequencies or high data rates.

Figs. 10 and 11 illustrate another embodiment of a flexible probe, wherein the functions of the elongate arm and the elongated lamina are combined into a single structure. 10, the probe tip 131 is disposed on the curved thin plate 133 such that the center of the probe tip 131 is located at a center of the support post 135 at both ends of the thin plate 133. [ And is located at a predetermined distance from the imaginary line connecting the center. The elongated thin plate 133 is twisted and bent by the normal force acting on the probe tip 131. The torsion is due to the torque generated because a force is applied at a position a certain distance from the center line of the support post 135. The amount of torsional deformation with respect to the amount of bending deformation of the thin plate beam is related to the offset of the probe tip 131 from the center line and the offset is expressed as a fraction of the length of the thin plate 133. [ Depending on the size of the element to be inspected and the material properties of the foil 133, the offset is preferably between 0.05 and 0.5 times the length of the foil 133. [

The probe of FIG. 10 includes a curved foil 133 supporting a probe tip 131 that deviates from the centerline of the support post 135. The electrical connection to the probe tip 131 is via the strip 133 to the contact terminal 134. The contact terminal 134 is again engaged with the post 135 and the post 135 is positioned on the contact pad 136 connected to the circuit trace 137. [ The circuit trace 137 is connected to the inspection circuit of the substrate 139 by a via 138. The vias 138 are positioned proximate to the probe tip to minimize inductance during connection from the test circuitry to the probe tip 131.

The fourth embodiment of the flexible probe includes the ground plane shield shown in Fig. The probe of FIG. 11 includes a curved thin plate 143 that supports the probe tip 141 at a position deviated from the center line of the support post 145. The electrical connection to the probe tip 141 is via the strip 143 to the contact terminal 144. The contact terminal 144 again engages the post 145 and the post 145 is positioned on the contact pad 146 connected to the circuit trace 147. The circuit trace 147 is connected to the inspection circuit of the substrate 149 by a via 148. The ground layer 140 is disposed under the probe tip 141 and electrically shields the probe to achieve high performance.

12A to 12C show Embodiment 3 in detail. 12A shows a typical configuration of the third embodiment, wherein the tip 151 is supported at the center point of the V-shaped flat plate 153 of spring material. The V-shaped plate 153 is supported by terminals 154 disposed at both ends of the plate. The plate of this embodiment is composed of Ti, Al 8, and V 4, which are titanium alloys, but other high strength materials or super plastic materials may also be used. The thickness of the plate 153 is between 10 and 75 micrometers, more preferably between 25 and 50 micrometers. The width of the narrowest portion of each arm is between 20 and 200 micrometers, and more preferably between 35 and 75 micrometers. The length between the center of the post 155 at the first end of the plate 153 and the center of the post 155 at the second end of the plate 153 is approximately 200 to 1000 micrometers. More preferably, the spacing between the centers of the posts is from 250 to 750 micrometers.

12B and 12C show the reaction that occurs when the force F is applied to the probe tip 151 of Embodiment 3. These are cross-sectional views of the probe before and after the force F acts. As shown in FIG. 12C, the force F applied to the probe tip 151 bends the curved thin plate 153 downward toward the substrate 159. The curved thin plate 153 is twisted and twisted by the bending force. The deformation in which the thin plate 153 is twisted and bent causes a counterforce against the deformation of the tip 151 as the force F acts.

The probe tip 151 is connected to the electrical circuit by a thin plate 153 and the thin plate 53 is supported by the posts 155 and the posts 155 are joined to the contact pads 154 of the thin plate 153 have. The posts 155 are located on the terminals 156 on the substrate 159 and the terminals 156 are again connected to the circuit traces 157. The circuit traces 157 are coupled to the electrical circuitry on the substrate 159 by conductive vias 158. Optionally, a ground plane may be inserted between the probe tip 191 and the circuitry of the substrate 199 to shield the probe tip 151 from signals of adjacent circuit traces on the substrate 159.

Flexibility The design of the leaf spring in the probe can be varied to meet the requirements for the inspection of a particular microelectronic device. Several designs are illustrated in Figures 13A-13C. In all cases, the probe tip is located at a position deviated from an axis determined by an imaginary line passing through the center between the posts that support the leaf spring at the first and second ends.

13A illustrates the probe 160 when the probe tip 161 is supported at the apex of the V-shaped portion 162 of the leaf spring 163. The V-shaped portion 162 is biased toward one end of the spring 163 to enable spring overlap, which is essential for achieving close spacing between the probe tips. The posts 165 and 167 are staggered and staggered so that each probe is closely spaced. Likewise, the contact pads 164, 166 on the corresponding end of the leaf spring 163 coincide with the posts 165, 167, respectively.

13B illustrates the probe 170 when the probe tip 171 is supported at the apex of the V-shaped portion 172 of the leaf spring 173. The V-shaped portion 172 is biased toward one end of the spring 173 to enable spring overlap, which is essential for achieving close spacing between the probe tips. The posts 175, 177 are staggered and staggered so that each probe is closely spaced. Similarly, the contact pads 174, 176 on the corresponding end of the leaf spring 163 coincide with the posts 175, 177, respectively.

13C illustrates a probe 180 when the probe tip 181 is supported at the apex of a curved leaf spring 182. FIG. The curved springs 182 have a shape that allows spring overlap, which is essential for achieving close spacing between the probe tips. The probe tip 181 is offset from the centerline between the center of the post 185 and the terminal 184 disposed at both ends of the spring 182.

The asymmetric configuration of the flexible probe shown in Figs. 14A-14D provides the performance required for use in particular inspection and burn-in. The asymmetric configuration facilitates contacting the contact pad with the probe when the space between the limited space, the corner and the pad is small. Furthermore, the ground contact can be incorporated into the probe structure to incorporate a ground shielding function.

The flexible probe 190 shown in FIG. 14A uses a post 195 and an additional post 197 to support the first end of the plate member 192. An additional post 197 is used to stabilize the structure against lateral acting forces. Further posts 197 are used to make electrical contact with the ground plane 199 included in the plate member 192. Post 197 is coupled to ground plane 199 at terminal 196. The plate member 192 is supported by a post 195 and the post 195 is coupled to the plate member 192 by a terminal 194.

The plate member 192 supports the probe tip 191. The probe tip 191 is disposed on the flat plate member 192 at a position deviated from the center axis 198 of the probe 190. The center axis is a phantom line connecting the center of the posts 195 and 197 supporting the first end of the plate member 192 and the center of the post 194 supporting the second end of the plate member 192. A force acting on the probe tip 191 generates a torque about a central axis 198 which causes the plate member 192 to bend and twist.

14B, the flexible probe 200 includes a leaf spring having a short arm 202 supported by a contact pad 206 and an elongate arm 203 supported by the contact pad 204. In FIG. The leaf spring supports the probe tip 201 disposed between the arm 202 and the arm 203 and located at a position deviated from the center line 208 of the probe 200. The center line 208 is a virtual line connecting the center of the post 205 and the center of the post 207. The force acting on the probe tip 201 generates a torque about the centerline 208 and the torque causes the arms 202 and 203 to bend and twist.

14C, the flexible probe 210 includes a leaf spring having a short arm 212 supported by a contact pad 216 and an elongated arm 213 supported by a contact pad 214. In FIG. The leaf spring supports the probe tip 211 located between the arm 212 and the arm 213 and located at a position off the center line 218 of the probe 210. The center line 218 is an imaginary line connecting the center of the post 215 and the center of the post 217. A force acting on the probe tip 211 generates a torque about the center line 218, and the torque causes the arms 212 and 213 to bend and twist.

14D, the flexible probe 220 includes a leaf spring having a short arm 222 supported by a contact pad 226 and a long arm 223 supported by a contact pad 224. The leaf spring supports the probe tip 221 located between the arm 222 and the arm 223 and located at a position away from the center line 228 of the probe 220. The center line 228 is a virtual line connecting the center of the post 225 and the center of the post 227. The force acting on the probe tip 221 generates a torque about the center line 228 and the torque causes the arms 222 and 223 to bend and twist to create a counter force that limits the probe tip 221 from further deforming .

Flexible probes according to the teachings of the present invention may be used for burn-in of wafers comprising integrated circuits and other microelectronic devices. The wafer contact apparatus 230 shown in Fig. 15A includes the probes 232 according to the third embodiment on the surface of the silicon substrate 231. Fig. The probe 232 is connected to the terminal 233 of the contact device 230 by the circuit trace 234 of the silicon substrate 231, respectively. In this example, silicon is used as a material for the substrate 231 and has a coefficient of thermal expansion that coincides with the thermal expansion coefficient of the silicon wafer including the integrated circuit during the burn-in test.

During the burn-in test, the contact device 230 is aligned with the wafer being inspected and supported by mechanical clamping means to direct the corresponding contact pads on the wafer with sufficient force to ensure that each probe of the contact device is in contact do. A force of 5-10 grams is enough to make a stable contact to contact a standard aluminum pad. Next, the assembly is heated to a burn-in temperature that is typically about 125 ° C to about 150 ° C. Electrical stimulation is applied to the circuit and dynamic burn-in is performed to operate each integrated circuit.

Fig. 15B shows a portion of the probe located on the surface of the contact device 230. Fig. The probe tips are arranged in a two-dimensional array coinciding with the two-dimensional array of contact pads on the flip chip being inspected. Each probe tip 241 is positioned to correspond to a corresponding contact pad on the flip chip. The size of the probe 232 is adapted to a grid spacing of between 150 micrometers and 500 micrometers, the spacing commonly used in flip chips. The probes 232 are arranged in an overlapping pattern so that each probe fits into a usable space. If the average density of the contact pads on the wafer is low, an additional nonfunctional probe is added to the array to locally support the wafer being examined.

The probe tip 241 of the probe 232 has a hard surface to penetrate the oxide on the aluminum bond pad on the wafer to be inspected. The probe tip 241 is located at the apex of the V-shaped spring 242 and the V-shaped spring 242 is supported by the post 245 coupled with the contact pad 244 at both ends of the spring 242.

The flexible probe according to the teachings of the present invention has means for inspecting the high-speed integrated circuit because the inherent and mutual inductance of each probe is low. A probe card 249 comprising a flexible probe is shown in Figure 16a. The probes 240 are suitable for inspecting a flip chip having a two-dimensional array of contact pads disposed in a two-dimensional array pattern on a substrate 248. Each probe 240 is electrically connected to a terminal 247 on a probe card 249 by a circuit trace means 246 included in a substrate 248. The substrate 248 preferably includes a size-stable base, such as alumina ceramic material, on which a circuit trace of copper is disposed between the layers of polyimide dielectric material.

16B shows an array of flexible probes 240 constructed in accordance with the teachings of Example 1 of the present invention. The probe tip 241 is disposed at the end of the arm 243 attached to the intermediate point of the extended leaf spring 242. The support posts 244 are engaged with contact pads 245 at both ends of the elongated leaf spring 242.

The chip socket shown in Figure 17A provides detachable means for inspecting, burning, and operating the flip chip. The flip chip 261 is supported by the positioning means 262 such that each contact pad on the flip chip 261 is mated with a corresponding probe 250 on the surface of the socket substrate 258. Each probe 250 is electrically connected to a terminal 257 on the socket substrate 258 by circuit trace means 256. An electrical signal suitable for operating the flip chip 261 is directed by the interconnect means 263 from the electronic circuit means 264 to the socket. The cable 265 connects the electronic circuitry 264 to a system for burning, inspecting, or operating the flip chip 261.

FIG. 17B shows a portion of the array of flexible probes 240 in the socket of FIG. 17A. The probe tip 251 is located at the end of the arm 253 attached to the intermediate point of the extended leaf spring 252. The support posts 254 engage the contact pads 255 at both ends of the elongated leaf spring 252.

The probe tip shown in Figs. 18A to 18D is configured to be suitable for a specific use in inspection and burn-in of a microelectronic device. Such probe tips and other tips are well known in the industry for the integrated circuit field. The examples presented herein represent many types of probe tips currently in use. Methods for manufacturing such probe tips are well known to those skilled in the art of making electrical contacts.

The probe tip shown in FIG. 18A is preferred for contacting the aluminum bond pad on the integrated circuit, and a sharp apex 273 is suitable for penetrating the oxide film of the aluminum bond pad. The pyramid 272 is formed by replicating the etched pits oriented in the silicon crystal plane 110. The pyramid 272 is supported on the thin film spring 271. The apex 273 of the pyramid 272 is sharply formed with an internal angle of 54.75 DEG between the opposed faces of the pyramid. A hard material selected from the group consisting of molybdenum, nickel, osmium, palladium, rhodium, rhenium, titanium, tungsten and alloys thereof is preferably used for the probe tip 272. Os, 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. 18B is preferable for contacting the noble metal contact pad. The thin film disk 277 is supported on a metal post 276 disposed on the surface of the leaf spring 275. The post 276 is etched at the bottom by a chemical etch process to expose the edge of the disc 277. The thin film disk 277 is preferably formed of an inert metal selected from the group consisting of gold, palladium 7, platinum, rhodium and alloys thereof.

The probe tip shown in Fig. 18C is preferred to be in contact with solder and other soft materials. The rounded metal tip 281 on the metal post 282 is disposed on the leaf spring 280. The metal tip 281 forms a rounded shape by backflushing the hot material into a spherical portion by flash laser melting. Suitable materials for the rounded metal tip 281 include metals selected from the group consisting of nickel, platinum, rhodium, copper-nickel alloys, beryllium-copper alloys and palladium 7.

The probe tip shown in Fig. 18D is preferable for contacting a small area contact pad and closely spaced pads. The probe tip 287 with the top edge 286 is disposed on the top side of the leaf spring 285. The probe tip 287 is preferably formed by plating the edge with a sacrificial material and then removing the sacrificial material leaving the edge metal 287.

It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (27)

A probe for electrical connection with a contact pad on a microelectronic element, (a) a thin plate made of a conductive material and having an upper side and a lower side; (b) a substrate having an upper side and a lower side; (c) electrical terminals disposed on an upper surface of the substrate; (d) a conductive post connected to one of the electrical terminals on the top side of the substrate at the other end, the thin plate being supported at a predetermined distance above the top side of the substrate, ; And (e) an electrically conductive tip having a base disposed on an upper side of the thin plate and having an upper side above an upper side of the thin plate; Wherein an upper surface of the conductive tip is adapted to electrically connect to a contact pad on the microelectronic element, Wherein the conductive tip is located on a thin plate at a predetermined distance from an imaginary line connecting each of the support posts so that the tip moves in the vertical direction as the thin plate is twisted and bent. The probe of claim 1, wherein the thin plate is a generally flat metal foil having a length of between 150 and 1500 micrometers and a thickness between 10 and 75 micrometers. The probe according to claim 1, wherein the thin plate is a metal film having a maximum thickness in a region immediately below the probe tip. The probe according to claim 1, wherein the conductive material is a metal selected from the group consisting of molybdenum, tungsten, columbium, nickel, titanium, beryllium-copper, stainless steel and alloys thereof. The method of claim 1, wherein the upper surface of the conductive tip is made of a hard metal selected from the group consisting of tungsten, titanium alloy, rhodium, rhenium, osmium, Paliney 7, nickel, chromium, . The method according to claim 1, A circuit pattern disposed under the electrically conductive tip and electrically connected to the thin plate, Further comprising: a probe. The probe according to claim 1, wherein the electrically conductive tip is a duplicate of a pyramidal pit etched to the surface of the single crystal silicon. The probe of claim 1, wherein the electrically conductive tip is a thin metal protrusion plated on a generally perpendicular edge protruding above the thin plate. The probe of claim 1, wherein the electrically conductive tip comprises a spherical portion of metal. 2. The method of claim 1, wherein the electrically conductive tip comprises a thin film of a hard metal supported by the post, and the lower side of the thin metal film is exposed so that the lower portion of the thin film is exposed. Probes. The probe of claim 1, wherein the post is an electroplated metal post. The method according to claim 1, An elastic dielectric material disposed between a thin plate of the conductive material and an upper surface of the substrate; Further comprising: a probe. 13. The probe of claim 12, wherein the elastic dielectric material is selected from the group consisting of silicon, fluorinated silicone, fluorocarbon and urethane elastomer. A probe for electrical connection with a contact pad on a microelectronic element, (a) an elongated thin film strip comprising an electrically conductive material and having an upper side and a lower side; (b) a support positioned at a first end and a second end of the elongated strip; And (c) an electrically conductive tip having a base disposed on an upper side of the elongated strip / RTI > The electrically conductive tip protruding from an upper surface of the elongated strip and being located a predetermined distance from a first end and a second end of the conductive strip, the center of the support at the first end and the second end Is located at a predetermined distance from an imaginary line connecting the center of the support portion in the probe. 15. The method of claim 14, Wherein the deformation of the elongated strip comprises twisting about an imaginary line connecting the center of the support at the first end and the center of the support at the second end. 15. The probe of claim 14, wherein the extended thin film strip comprises a conductive thin plate, a metal thin film and a thin film dielectric material. 15. The probe of claim 14, wherein the elongated thin film strip comprises a planar metal foil in which the pattern is formed, and wherein the pattern is curved in a direction parallel to the strip. 15. The probe of claim 14, wherein the first support comprises a first metal post and the second support comprises a second metal post. A socket for a microelectronic device having a generally planar surface on which a contact pad array is disposed, (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, for electrically connecting the contact pads; And (c) circuit means coupled to the flexible probe for causing the microelectronic device to operate when the flexible probe is connected to the contact pad; and / RTI > Each of said flexible probes comprising an elongated strip of thin film made of a conductive material and having a first end and a second end, Said elongated strip being supported by at least one post at said first end and by at least one post at said second end, Wherein the probe tip is positioned at a predetermined distance from the first end and the second end, and the probe tip is moved from a virtual line connecting the center of the post at the first end to the center of the post at the second end, Of the socket (10). 20. The socket for a microelectronic device according to claim 19, wherein the array of contact pads is a regular area array having the same number of rows and columns of contact pads. 20. The socket for a microelectronic device according to claim 19, wherein the array of contact pads is arranged in a linear array of contact pads. 20. The socket for a microelectronic device according to claim 19, wherein the substrate is made of a silicon material. 21. The socket for a microelectronic device according to claim 20, wherein the microelectronic element is a plurality of integrated circuits arranged on a non-cut silicon wafer. 21. The socket for a microelectronic device according to claim 20, wherein the silicon material is a silicon wafer having a thickness of 200 mu m to 1000 mu m. 20. The socket for a microelectronic device according to claim 19, wherein the substrate is made of a ceramic material. 26. The socket for a microelectronic device of claim 25, wherein the substrate is a metal-ceramic multilayer structure, each probe connected to circuit means for inspecting and burning the microelectronic device. 20. The method of claim 19, A ground electrode integrated on the top side of the substrate and having an area generally below the extended strip of the thin film, Further comprising a plurality of openings formed in the sockets.