JP2006317294A - Probe card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a probe card capable of bringing a probe to contact with an object to be tested in its over-drive state in which the load does not exceed a prescribed value. <P>SOLUTION: A contact unit 2 is made up by attaching a metal plate 25 to a contact board 20 having a probe 21, and is hung from a main board 10 so as to be movable vertically by a flexible board 30. Therefore, when the contact unit 2 is raised by the object to be tested 40 being in contact with the probe 21, the probe 21 is applied practically with the weight of the contact unit. This load is kept constant even when the over-drive amount is varied, thereby preventing an excessive needle load from applying to the probe. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a probe card, and more particularly to an improvement of a probe card used when inspecting electrical characteristics of an inspection object such as a device formed on a semiconductor wafer.

  A probe card is an electrical connection means for bringing a probe (contact probe) into contact with an electrode pad of a semiconductor integrated circuit and taking out an electrical signal of the electrode pad. Generally, a multilayer wiring board is used. A plurality of probes are arranged on the multilayer wiring board corresponding to the number and pitch of the electrode pads of the semiconductor integrated circuit, and electrical signals input from the probes are guided to external terminals arranged at predetermined intervals through the multilayer wiring board. It is configured to be.

  When using this probe card to inspect the electrical characteristics of a device on a semiconductor wafer, the probe card is attached to the probe device, and the electrical signal of the external terminal of the probe card can be taken out of the probe device. After making the appropriate connection, the probe is pressed against the electrode pad on the semiconductor wafer.

  In order to conduct the probe and the electrode pad well, it is necessary not only to contact the probe with the electrode pad but also to apply a predetermined needle load to the probe and press the probe against the electrode pad. In particular, when there is a slight difference in height between multiple electrode pads, after some probes and electrode pads are in contact, all probes are further pressed to contact each electrode pad (overdrive). Has been done.

  Further, a probe device that tilts the probe card according to the tilt of the semiconductor wafer when the probe card and the semiconductor wafer are not parallel has been proposed (for example, Patent Document 1). The probe device described in Patent Document 1 presses the probe card using a swingable pusher, so that the probe card is also tilted according to the tilt of the wafer, and the probe is pressed against the electrode pad and brought into contact with the probe card. Yes.

  In practice, the probe card is fixed above the semiconductor wafer with a space, the semiconductor wafer placed on a vertically movable table is lifted, and the electrode pads of the device on the semiconductor wafer are brought into contact with the probe. And assuming that there is a height difference in the electrode pad and the case where the probe card and the semiconductor wafer are not parallel, the probe card and the semiconductor wafer Are pressed together with great force (overdrive). This overdrive ensures that all probes are in contact with the electrode pads.

JP-A-8-83824

  Although overdrive is performed to ensure that all probes are in contact with the electrode pads to be inspected, excessive overdrive has a problem of causing deformation and further damage of the probe. When the number of electrode pads of the device to be inspected is as small as about 100, if the load per one is, for example, 3 grams, a total force of 300 grams is applied. In addition, there are multiple areas to be inspected on the surface of the semiconductor wafer, and each time the area to be inspected is changed, an overdrive load is applied. A load of kilos to tens of kilos was to be applied many times. Therefore, in the case of a probe card having several thousand probes, each probe has a very fine diameter shape of several μm to several tens of μm as the number increases. The structure and materials that can withstand the overdrive load were studied, and the limit was almost reached.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a probe card capable of bringing a probe into contact with an inspection object in an overdrive state in which a predetermined load is not exceeded.

  A probe card according to a first aspect of the present invention includes a main board and a contact unit suspended from the main board so as to be movable up and down. The contact unit includes at least a contact board, and the contact board has a surface. A plurality of probes are formed on the surface, the back surface is opposed to the lower surface of the main substrate, and the contact unit has a weight corresponding to a predetermined overdrive load.

  With such a configuration, in the overdrive state in which each probe is brought into contact with the inspection object, the contact unit is lifted from below by the inspection object, and the contact unit can be moved up and down with respect to the main substrate. Substantially only the weight of the contact unit is added. For this reason, the contact unit balances itself according to the inspection object, the contact substrate becomes parallel to the inspection object, and the overdrive load can be set to a predetermined value.

  In the probe card according to the second aspect of the present invention, in addition to the above configuration, the contact unit includes the contact substrate and a load member, the load member is attached to the contact substrate, and the load of the predetermined overdrive is detected. The weight is obtained by subtracting the weight of the contact substrate.

  With such a configuration, by adjusting the weight of the load member, it is possible to arbitrarily determine the overdrive load regardless of the weight of the contact substrate. In particular, even when the contact substrate has a large number of probes and a large overdrive load is required, a desired load can be secured.

  In addition to the above configuration, the probe card according to the third aspect of the present invention is configured such that the center of gravity of the contact unit is within the arrangement region of the probe on the contact substrate. With such a configuration, an overdrive load can be applied to each probe accurately and evenly.

  According to a fourth aspect of the present invention, in addition to the above configuration, the probe card includes a metal needle formed by electroforming. By forming the probe by electroforming, it is possible to arrange a probe with a narrow pitch and a short stroke on the contact substrate. Therefore, while the number of probes can be increased, a larger load is required as an overdrive load, and it is required to make the contact substrate and the inspection object parallel with higher accuracy. The present invention is suitable for such a probe card.

  In the probe card according to a fifth aspect of the present invention, in addition to the above configuration, the contact substrate is made of a silicon substrate. With such a configuration, when the object to be inspected is an integrated circuit on a silicon substrate, it is suitable for, for example, a temperature test and the like because no displacement occurs according to the temperature.

  In addition to the above configuration, the probe card according to the sixth aspect of the present invention is configured such that the contact substrate has a linear expansion coefficient of −3 ppm / ° C. or more and 8 ppm / ° C. or less. With such a configuration, when the object to be inspected is an integrated circuit on a silicon substrate, even if the contact substrate is not a silicon substrate, no significant positional deviation occurs according to the temperature. Suitable for testing and the like.

  In the probe card according to the present invention, in the overdrive state, the contact unit is lifted from below by the object to be inspected, and the contact unit can be moved up and down with respect to the main board. Only added. At this time, the contact unit balances itself following the inspection object, the contact substrate becomes parallel to the inspection object, and the overdrive load can be set to a predetermined value. Accordingly, the probe can be brought into contact with the inspection object in an overdrive state in which the predetermined load is not exceeded.

Embodiment 1 FIG.
FIG. 1 is an external view showing an example of a probe card 1 according to Embodiment 1 of the present invention. The main board 10 and the contact board 20 are gently engaged by the flexible board 30, and the contact board 20 is suspended from the main board 10 in a state where the main board 10 is horizontally held by the probe device, and the flexible board Within a range limited by 30, the main substrate 10 is displaceable and swingable.

  The main substrate 10 is a substrate that is detachably attached to the probe device and supports the contact substrate 20 and the flexible substrate 30. Here, a glass epoxy multilayer wiring board having a circular shape is used as the main board 10. A large number of external terminals 11 are formed on the peripheral edge of the main substrate 10. These external terminals 11 are terminals for electrical connection with a signal terminal of a tester (not shown), and are provided on the upper surface or the lower surface of the main substrate 10 depending on the configuration of the probe device. These external terminals 11 are connected to the terminals of the microconnector 12 formed at a position closer to the center via the multilayer wiring of the main substrate 10.

  The contact substrate 20 is a substrate in which a large number of probes 21 are formed on the surface of the contact substrate 20 and the back surface of the contact substrate 20 is suspended from the lower surface of the main substrate 10. Here, a rectangular silicon substrate is used as the contact substrate 20. The probe 21 is a metal needle formed by electroforming, and details thereof will be described later. Electrode pads are provided on the periphery of the back surface of the contact substrate 20, and these electrode pads are connected to the main substrate 10 via the flexible substrate 30.

  The flexible substrate 30 is an assembly of conductive wires that electrically connect the main substrate 10 and the contact substrate 20, and a wiring pattern is formed on a thin insulating substrate having flexibility. Here, a film substrate having a shape in which the main substrate 10 side is branched into three is used, and a microconnector 31 that is detachably engaged with the microconnector 12 of the main substrate 10 is provided at the end of each branch portion. Are provided. As the film substrate, polyimide, glass epoxy, TLCP (Thermotropic Liquid Crystal Polymer), or the like can be used.

  2 to 4 are diagrams illustrating a detailed configuration example of the contact substrate 20. FIG. 2 shows an example of the appearance on the front side, FIG. 3 shows an example of the appearance on the back side, and FIG. 4 shows another example of the appearance on the back side. Probes 21 and wiring patterns 23 are formed on the surface of the contact substrate 20. A region where the probe 21 is formed is a probe arrangement region 24. In the present embodiment, a large number of probes 21 are arranged in two rows at the center of the surface of the contact substrate 20, and the probe arrangement region 24 is a rectangular region surrounded by these probes 21. One end of the wiring pattern 23 is connected to the probe 21 and the other end extends to the peripheral edge while increasing the pitch between the wirings.

  On the other hand, on the back surface side of the contact substrate 20, metal plates 25, 25a to 25d are attached to the central portion, and electrode pads 22 are formed on the peripheral portion. The wiring pattern 23 on the front surface side is connected to the electrode pad 22 through a through hole (not shown) penetrating the contact substrate 20 at the peripheral edge. Each electrode pad 22 is bump-bonded with a terminal 32 of a flexible substrate 30 and connected to the main substrate 10.

  In FIG. 3, a metal plate 25 having a rectangular shape is attached to the back surface of the contact substrate 20, leaving the peripheral edge where the electrode pads 22 are formed. For example, plate-like molybdenum (Mo) is used as the metal plate 25. In FIG. 4, four metal plates 25 a to 25 d are attached on the contact substrate 20. The contact substrate 20 and the metal plates 25 (or 25a to 25d) constitute a contact unit 2 that is supported by the main substrate 10 so as to be freely displaceable and swingable.

  When the contact unit 2 is lifted by the object to be inspected, the contact unit 2 is in a free state during overdrive, and substantially only the weight of the contact unit 2 is applied to each probe 21. That is, the weight of the contact unit 2 corresponds to the overdrive load. For this reason, if the weight of the contact unit 2 is adjusted by sticking the metal plates 25 and 25a to 25d to the contact substrate 20, a predetermined overdrive load can be secured.

  Furthermore, the contact substrate 20 can be reinforced by sticking the metal plates 25, 25 a to 25 d to the back surface of the contact substrate 20. In this way, by using the metal plates 25, 25a to 25d as the load member and the reinforcing member, the weight of the contact unit 2 corresponding to the overdrive load is ensured regardless of the material and shape of the contact substrate 20. Since the structural strength can also be improved, the degree of freedom in selecting the material and shape of the contact substrate 20 can be increased.

  Further, in order to uniformly apply a needle load to each probe 21 during overdrive, the metal plates 25 and 25a to 25d are arranged so that the center of gravity of the contact unit 2 is located in the probe arrangement region 24. Is desirable. For example, in FIG. 3, the metal plate 25 has a symmetrical shape with a point in the probe arrangement region 24 as the center, and in FIG. 4, a plurality of metal plates 25a to 25d are symmetrically arranged with the point as the center. Yes.

  Note that the metal plates 25 and 25a to 25d may not be used if a desired overdrive load can be obtained only by the weight of the contact substrate 20. In this case, the contact unit 2 is constituted only by the contact substrate 20.

  For example, when 1000 probes 21 are formed on the contact substrate 20 and the needle load per one necessary to overdrive these probes 21 is 0.5 g, the weight of the contact unit 2 is 500g is required. On the other hand, since the specific gravity of silicon is 2.33 at room temperature, the contact substrate 20 made of a silicon substrate having a square with a side of 5 cm and a thickness of 400 μm is 2.33 g. Therefore, if about 498 g of the metal plate 25 corresponding to these differences is attached to the contact substrate 20, the weight of the contact unit 2 can be made 500 g.

  If the contact substrate 20 is made thicker, the weight can be increased to 500 g without using the metal plate 25. However, if the contact substrate 20 becomes thicker, it becomes difficult to process the through holes of the contact substrate 20, so it is desirable to attach a metal plate 25 having a weight corresponding to the shortage to the contact substrate 20.

  Furthermore, if the probes are formed by electroforming, 5000 to 10000 probes 21 can be formed on the contact substrate 20. Usually, a needle load of 0.1 to 5 g is required, and if the number of probes is 5000 to 10,000, an overdrive load of several kg or more is required. In such a case, a sufficient overdrive load cannot be ensured only by the weight of the contact substrate 20, and the insufficient weight needs to be compensated by the metal plate 25.

  FIGS. 5A and 5B are diagrams showing the probe card 1 attached to the probe apparatus. FIG. 5A shows a state before contact with the silicon wafer 40 and FIG. Each after contact is shown. A silicon wafer 40 as an inspection object is placed on a movable table 41 with the surface on which the integrated circuit is formed facing upward, and is vacuum-sucked. After the movable table 41 is moved or rotated in a horizontal plane and the probe 21 and the silicon wafer 40 are aligned, the movable table 41 is raised to bring the probe 21 into contact with the electrode pad on the silicon wafer 40, and An inspection of the electrical characteristics of the integrated circuit is performed.

  The contact substrate 20 before contact is suspended by the flexible substrate 30 at a position corresponding to the length of the flexible substrate 30 so as not to drop off from the main substrate 10. That is, the contact substrate 20 receives a reaction force having a vertical component corresponding to the weight of the contact unit 2 from the flexible substrate 30.

  At the time of inspection, the probe 21 is overdriven by stopping the movable table 41 at a predetermined inspection position. This inspection position is determined in advance as a position that is higher than the position at which the probe 21 starts to contact the silicon wafer 40 and that does not allow the contact unit 2 to contact the main substrate 10. That is, at the time of overdrive, the contact substrate 20 is slightly lifted by the silicon wafer 40, and the flexible substrate 30 is bent.

  At this time, the vertical component of the force received by the contact substrate 20 from the flexible substrate 30 is negligible compared to the weight of the contact unit 2. Accordingly, the total needle load applied to each probe 21, that is, the overdrive load substantially matches the weight of the contact unit 2.

  According to the inventor's experiment, the vertical component of the force that the contact substrate 20 receives from the flexible substrate 30 in a state where the silicon wafer 40 is in contact with the probe card 1 is less than 10 g. That is, if the weight of the contact unit 2 is 500 g or more, it is less than 2%. Therefore, if the flexible substrate 30 having sufficient flexibility is used, the influence of the force received by the contact substrate 20 from the flexible substrate 30 on the needle load of the probe 21 can be ignored.

  Further, the contact substrate 20 lifted by the silicon wafer 40 is in a free state in which the contact substrate 20 is displaceable and swingable with respect to the main substrate 10. The inclination of the contact substrate 20 with respect to the silicon wafer 40 is determined by each probe 21. It is determined only by the reaction force received from. That is, it is possible to determine the inclination of the contact substrate 20 by balancing the contact substrate 20 in the free state on the silicon wafer 40. Therefore, even when there is a difference in height between the electrode pads on the silicon wafer 40, the tilt adjustment can be performed with high accuracy that is not compared with a technique using a conventional mechanical swing mechanism. .

  6A and 6B are diagrams showing an example of the relationship between the overdrive load and the amount of overdrive. FIG. 6A shows the case of the probe card 1 according to the present embodiment, and FIG. 6B shows the case of the conventional probe card. Are shown respectively. The overdrive amount is a distance by which the movable table 41 is further raised with reference to the state where the probe 21 starts to contact the electrode pad. The overdrive load is the sum of the loads applied to the probes 21. is there.

  In the case of the conventional probe card, since the probe 21 is fixed to the main board 10, as shown in FIG. 6B, if the overdrive amount is increased over the entire section, the overdrive load also increases. . In this figure, when the overdrive amount is H1, a desired overdrive load Fa is applied to the probe 21, but when the overdrive amount reaches Hy, the fracture limit load Fb is applied to the probe 21. The The fracture limit load Fb is a maximum value of an overdrive load that can plastically deform the probe 21. If an overdrive load exceeding the fracture limit load Fb is applied, the probe 21 is broken.

  For this reason, when a conventional probe card is used, it is necessary to control the raising / lowering drive of the movable stage 41 with high accuracy in order to apply a desired needle load to the probe 21 without destroying the probe 21. Furthermore, even if the height of the movable stage 41 is driven with high accuracy, due to the inclination of the object to be inspected with respect to the probe card, the height difference of the electrode pad of the object to be inspected, and the variation for each of these objects to be inspected, It was not easy to give a desired needle load to each probe 21.

  On the other hand, when the probe card according to the present embodiment is used, as shown in FIG. 6A, the change in overdrive load can be divided into three sections A1 to A3. The section A1 in which the overdrive amount is equal to or less than H1 is a section in which only some of the probes 21 are in contact with the silicon wafer 40. If the overdrive amount is increased, the overdrive load increases.

  In the section A2 where the overdrive amount is H1 to H2, the overdrive load is constant even if the overdrive amount is increased. In this section A2, even if the overdrive amount is increased, the contact unit 2 is lifted correspondingly and the height thereof only changes. Regardless of the overdrive amount, each probe 21 has a contact unit 2 An overdrive load Fa corresponding to the weight is applied.

  In the section A3 where the overdrive amount is H2 or more, the contact unit 2 comes into contact with the main substrate 10, and the overdrive load starts to increase again according to the overdrive amount. As a result, if the overdrive amount reaches Hx, the fracture limit load Fb is applied to the probe 21.

  That is, the needle load does not change in the section A2 even if the movable stage 41 is driven upward, and the desired needle load Fa is always obtained in the section A2 if the weight of the contact unit 2 is adjusted in advance. be able to. Also, by providing the section A2, the section length in which the overdrive amount in FIG. 6A is H1 to Hx is larger than the section length in FIG. 6B in which the overdrive amount is H1 to Hy. become longer. That is, it is possible to lengthen the overdrive section in which the probe 21 is not destroyed and a desired overdrive load can be secured. Therefore, high accuracy is not required for the drive control of the movable stage 41, and it is possible to suppress the probe 21 from being damaged due to an excessive needle load.

Embodiment 2. FIG.
In the first embodiment, the example in which the probes 21 are arranged in two rows in the probe arrangement region 24 on the contact substrate 20 has been described. However, the present invention is limited to such a case. is not.

  FIG. 7 is a diagram showing an example of a probe card according to the second embodiment of the present invention. In this probe card, probes are arranged in a matrix in a probe arrangement region 24 in the center of the contact substrate 20. In this manner, the probes 21 may be arranged in three or more rows in the probe arrangement region 24. Moreover, other arbitrary arrangement | positioning may be sufficient.

  In the above embodiment, since a silicon substrate is used as the contact substrate 20, good contact with the object to be inspected can be obtained regardless of temperature conditions. Usually, the probe 21 is disposed at a position on the contact substrate 20 corresponding to the position of the electrode pad of the inspection object. For this reason, if the contact substrate 20 expands or contracts according to the temperature, the pitch of the probes 21 also changes. Similarly, the pitch of the electrode pads also changes according to the temperature. Therefore, when the object to be inspected is an integrated circuit formed on a silicon substrate, if the contact substrate 20 containing silicon as a main component is used, the thermal expansion coefficients of both can be made to coincide with each other, regardless of the temperature conditions. Therefore, a good contact can be obtained.

  Further, a substrate made of a material other than silicon can be used as the contact substrate 20. For example, an insulating film made of polyimide, glass epoxy, TLCP, or the like can be used as the contact substrate 20. In this case, a part of the flexible substrate 30 serving as a conductive wire can be used as the contact substrate 20 and the two can be integrally formed. However, when a contact substrate 20 other than a silicon substrate is used, it is desirable to use a material having a thermal expansion coefficient close to that of silicon. Since the linear expansion coefficient of silicon is 2 to 4 ppm / ° C., it is desirable to use a material having a linear expansion coefficient of −3 to 9 ppm / ° C. for the contact substrate 20.

  Moreover, the probe 21 is not limited to what was formed by the electrocasting method. For example, a so-called cantilever type probe having a sharpened tip of a leaf spring-like metal can be used.

  In addition, in FIG. 6A, an example in which the needle load is constant in the section A2 has been described as the most preferable embodiment, but the present invention is not necessarily limited to such a case. That is, the section A2 in which the desired overdrive load Fa is obtained exists in the overdrive amounts H1 to Hx, and the average value of the overdrive load gradient in the section A2 is the overdrive load in the other sections A1 and A3. It only needs to be smaller than the average value of the slopes of. In FIG. 6A, for convenience, the characteristics in the sections A1 and A3 are shown by straight lines, but it goes without saying that the present invention is not limited to such a case.

It is the external view which showed an example of the probe card 1 by Embodiment 1 of this invention. It is the figure which showed the detailed structural example of the contact board | substrate 20 of FIG. 1, and the external appearance of the lower surface side is shown. It is the figure which showed the detailed structural example of the contact board | substrate 20 of FIG. 1, and an example of the external appearance of the upper surface side is shown. It is the figure which showed the detailed structural example of the contact board | substrate 20 of FIG. 1, and the other example of the external appearance of the upper surface side is shown. It is the figure which showed the probe card 1 attached to the probe apparatus, and the mode before and after contact with a silicon wafer is shown. It is the figure which showed an example of the relationship between overdrive load and overdrive amount. It is the figure which showed an example of the probe card 1 by Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Probe card 2 Contact unit 10 Main board 11 External terminal 12 Micro connector 20 Contact board 21 Probe 22 Electrode pad 23 Wiring pattern 24 Probe arrangement area 25, 25a-25d Metal plate 30 Flexible board 32 Terminal 40 Silicon wafer 41 Movable table

Claims (6)

A main board and a contact unit suspended vertically from the main board;
The contact unit has at least a contact substrate,
In the contact substrate, a plurality of probes are formed on the front surface, the back surface is opposed to the lower surface of the main substrate,
The probe card, wherein the contact unit has a weight corresponding to a predetermined overdrive load. The contact unit comprises the contact substrate and a load member,
The probe card according to claim 1, wherein the load member is attached to the contact board and has a weight obtained by subtracting a weight of the contact board from a load of the predetermined overdrive.   3. The probe card according to claim 1, wherein the center of gravity of the contact unit is in an arrangement region of the probe on the contact substrate.   The probe card according to claim 1, wherein the probe is made of a metal needle formed by electroforming.   3. The probe card according to claim 1, wherein the contact substrate is made of a silicon substrate.   The probe card according to claim 1, wherein the contact substrate has a linear expansion coefficient of −3 ppm / ° C. or more and 8 ppm / ° C. or less.

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