Probe card

Abstract

To provide a highly convenient probe card capable of improving reliability and durability and achieving a part or whole of mass production.SOLUTION: A probe card 1 includes: a coaxial cable 70 through which a high frequency test signal is input from an outside; and a coaxial probe 10 which has flexibility and has a proximal end part connected to the coaxial cable 70 and a distal end part in contact with an electrode of a measurement target object (wafer 90). In the distal end part of the coaxial probe 10, an inner conductor comes into contact with a signal electrode of the wafer 90 and outer conductors come into contact with ground electrodes of the wafer 90. In the coaxial probe 10, distal end parts of an inner insulation body and an outer insulation body do not come into contact with a protection film even when the inner conductor is bent in a case where the inner conductor comes into contact with the signal electrode of the wafer 90 with the protection film disposed thereon, and a coaxial structure is kept immediately before the protection film.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a probe card used for testing the electrical characteristics of high-frequency devices.

Background Art

[0002] In recent years, in the field of high-speed communication such as smartphones, since the commercialization of 5G (the fifth-generation mobile communication system) started in 2020, the development of 5G high-frequency devices has been progressing. Accordingly, the development of probe cards required for testing the electrical characteristics of high-frequency devices (high-frequency device chips) used at 5G frequencies has also been progressing.

[0003] 5G high-frequency devices support various fields such as industrial smartization, logistics, construction, agriculture, health care, education, and remote offices, and mass production of probe cards is required. At the same time, probe cards are also required to have reliability, for example, suppressing signal attenuation and impedance variations during wafer testing, and durability.

[0004] Here, as prior arts related to probe cards, there are those shown in Patent Documents 1 to 4. Patent Document 1 describes a probe card capable of improving the measurement accuracy of electrical characteristics. Specifically, it describes a probe card 100 including a probe pin 10 made of a metal conductor and elastically deformable, with a tip portion 11 protruding from an end face 72A, and a cable 30 having a core 31 made of an electrical conductor electrically connected to the probe pin 10 and an inspection device, and an insulating coating 32 made of an insulator covering the core 31 (see FIG. 1). And in the probe card 100, the base end portion 11 of the probe pin 10 and the tip portion of the core 31 are in direct contact.

[0005] In addition, Patent Document 2 describes a probe card equipped with a vertical probe needle that prevents a decrease in contact stability with respect to an object to be inspected and enables repeated use over a long period of time. Specifically, this vertical probe needle is composed of a metal wire 1 with a wire diameter of 0.02 to 0.04 mm and a length of 3.0 to 6.0 mm, in which the body portion 1b is coated with an insulating film 2 of SiO2, and a metal film 3 having granular protrusions 3a is formed at the tip portion 1a. The edge 2a of the insulating film 2 is located at a distance of 20 to 60 μm from the apex 5, and the apex 5 is formed in an arc shape having a radius of curvature of 26 to 45 μm in a longitudinal sectional view (see Fig. 1).

[0006] In addition, Patent Document 3 describes a probe card using a probe aimed at maintaining electrical isolation of the probe and ensuring impedance matching of the needle to enhance the inspection accuracy of high-frequency electrical characteristics. Specifically, it describes a probe 1 including a coaxial cable 2 having an inner conductor 21, an insulator 22 covering the inner conductor 21, and an outer conductor 23 covering the insulator 22, a first probe 3 electrically connected to the inner conductor 21 of the coaxial cable 2, and an auxiliary conductor 4 electrically connected to the outer conductor 23 and arranged to cover the front side of the first probe 3 (see Fig. 1). Further, the probe 1 includes a connecting conductor 6 connecting the auxiliary conductor 4 and a second probe 5.

[0007] Furthermore, Patent Document 4 describes a coaxial probe aimed at suppressing impedance fluctuations even when the distance between the signal pad and the ground pad of the measurement object differs from the distance between the signal terminal and the ground terminal. Specifically, the coaxial probe 1 includes a coaxial line portion 12 having an inner conductor 121 and an outer conductor 122, a signal terminal 124 formed by extending the inner conductor 121, a ground terminal 125 formed by extending the outer conductor 122 and arranged side by side with the signal terminal 124, and a cylindrical structure having a hole 131 into which the signal terminal 124 can be inserted, and a mounting signal conductor 13 mounted on and electrically connected to the signal terminal 124 (see Fig. 4).

Prior Art Documents

Patent Documents

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2023-022720 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-181045 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-194412 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-180746 [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] However, in the probe card described in Patent Document 1, since the base end portion of the probe pin and the tip end portion of the core of the cable are in direct contact, compared with the case where the probe pin and the core of the cable are connected via intervening members such as connectors, soldering portions, and coaxial pins that have poor transmission loss at high frequencies, deterioration of the electrical signal obtained via the probe pin can be suppressed, and improvement in the measurement accuracy of electrical characteristics such as chips on a semiconductor wafer to be inspected can be achieved. However, further improvement in the measurement accuracy of electrical characteristics cannot be achieved.

[0010] This is because the probe structure disclosed in Patent Document 1 consists only of a conductive probe pin and an insulating film, and does not have a shield structure (a structure in which the signal line is surrounded by a dielectric and an outer conductor like a coaxial cable) that prevents signal loss and the like in the high-frequency region. Therefore, with the structure of Patent Document 1, improvement in the measurement accuracy of electrical characteristics due to the shield effect (the effect of protecting the internal signal from external signal interference and the effect of preventing external leakage of the internal signal) that prevents signal loss and the like in the high-frequency region cannot be achieved.

[0011] Note that the probe card (vertical probe needle) described in Patent Document 2 also forms a metal film having granular protrusions 3a at the tip 1a of the probe needle, thereby preventing a decrease in contact stability with the object to be inspected and enabling repeated use over a long period of time. However, since the structure of the probe needle is a metal fine wire and an insulating film surrounding it (not a shield structure) as in Patent Document 1, it has no effect on signal loss in the high-frequency region.

[0012] On the other hand, the probe card described in Patent Document 3 is provided with an auxiliary conductor that is electrically connected to an external conductor and is arranged so as to cover the front side of the first signal line probe in order to maintain the electrical isolation of the probe and ensure impedance matching of the needle, thereby enhancing the inspection accuracy of high-frequency electrical characteristics. Further, as its effects, it is described that the increase in impedance can be suppressed in FIG. 14 and noise reduction of 10 to 20 dB can be achieved in FIG. 14.

[0013] However, only the portion with the auxiliary conductor centered around the internal conductor has a shielding effect, and there is no auxiliary dielectric in other directions, so the shielding effect cannot be obtained. As shown in FIG. 14, this is clearly understood from the fact that there is a difference of 3 Ω from the coaxial portion.

[0014] Also, FIGS. 14 and the like in Patent Document 3 show that when the auxiliary conductor is provided, there is noise reduction of 10 to 20 dB compared to the case where it is not provided, but the measurement frequency is 10 MHz to 6 GHz, which is lower than the frequency of 5G. Since it is a well-known fact that noise increases as the frequency increases, this frequency band may be sufficient, but in a high-frequency band of 5G or higher, it cannot be said that noise reduction can be sufficiently achieved with this structure.

[0015] Furthermore, even when the distance between the signal pad and the ground pad of the object to be measured is different from the distance between the signal terminal and the ground terminal, the coaxial probe described in Patent Document 4 suppresses impedance fluctuations and has a coaxial line portion 12 having an inner conductor 121 and an outer conductor 122 in order to obtain sufficient resolution. It also has a signal terminal 124 formed by extending the inner conductor 121, a ground terminal 125 formed by extending the outer conductor 122 and arranged side by side with the signal terminal 124, and is a cylindrical structure having a hole 131 into which the signal terminal 124 can be inserted, and is provided with a mounting signal conductor 13 mounted on and electrically connected to the signal terminal 124.

[0016] Thus, the ground terminal 125 of the coaxial probe described in Patent Document 4 is a simple straight line, and does not have a coaxial structure surrounding the periphery of the signal terminal 124 that can prevent leakage of high-frequency signals, and cannot prevent signal loss in a high-frequency band of 5G or higher.

[0017] Specifically, as shown in FIG. 5(a), the improved pass characteristic (corresponding to the insertion loss described later) is -4 dB at 20 GHz, which is only a performance of the prior art level. Also, as shown in FIG. 5(b), the improved impedance is also about 55 Ω.

[0018] As described above, the inability to improve the measurement accuracy of the above-described further electrical characteristics means that, for example, in the probe card described in Patent Document 1, in a 5G high-frequency band (about 28 GHz), the insertion loss exceeds the standard (within -2.0 dB). Also, regarding the probe card described in Patent Document 1, even if a structure for preventing signal loss as described in Patent Documents 3 and 4 is used to suppress reflection, it would have been sufficient in the conventional high-frequency band up to 4G, but in a high-frequency band of 5G or higher, it cannot satisfy the standards for insertion loss and impedance variation (within 50.0 Ω ± 5%).

[0019] Therefore, there is a need for a probe card that can improve at least one or more of these exemplified standards. Based on the above-described background, there is a demand for further improvement in convenience of the probe card, including the ability to improve reliability and durability and the ability to achieve mass production.

[0020] Therefore, an object of the present invention is to provide a highly convenient probe card that can achieve some or all of the improvement in reliability and durability and mass production.

Means for Solving the Problem

[0021] The probe card according to the present invention is a probe card for measuring the electrical characteristics of a measurement object, a coaxial cable to which a test signal is input from the outside, and a coaxial probe having flexibility, a base end portion of which is connected to the coaxial cable and a tip end portion of which contacts an electrode of the measurement object, and is provided with at the tip end portion of the coaxial probe, the inner conductor contacts the signal electrode of the measurement object, and the outer conductor contacts the ground electrode of the measurement object, when the inner conductor of the coaxial probe contacts the signal electrode of the measurement object provided with the protective film, the tip end portions of the inner insulator and the outer insulator do not contact the protective film even if the inner conductor is bent, and the coaxial structure is maintained up to immediately before the protective film.

[0022] With such a configuration, the probe card according to the present invention has a coaxial structure to such an extent that the coaxial probe does not damage the protective film of the measurement object. Therefore, the insertion loss can be reduced to an extremely low level.

[0023] The probe card also has an intermediate layer provided between the coaxial cable and the coaxial probe, and has an intermediate layer including an inner conductor and an outer conductor, and it is desirable that the inner conductor and the outer conductor of the intermediate layer are respectively connected to the inner conductor and the outer conductor of the coaxial probe and the inner conductor and the outer conductor of the coaxial cable.

[0024] Thus, by providing an intermediate layer including an inner conductor and an outer conductor between the coaxial cable and the coaxial probe, it is possible to suppress a change in the characteristic impedance of the connection portion between the coaxial cable and the coaxial probe.

[0025] In particular, in this intermediate layer, the outer diameter of the inner conductor of the intermediate layer on the coaxial cable side is equal to or less than the outer diameter of the inner conductor of the coaxial cable, and / or the inner diameter of the outer conductor of the intermediate layer on the coaxial cable side is equal to or less than the inner diameter of the outer conductor of the coaxial cable. The outer diameter of the inner conductor of the intermediate layer on the coaxial probe side is equal to or greater than the outer diameter of the inner conductor of the coaxial probe, and / or the inner diameter of the outer conductor of the intermediate layer on the coaxial probe side is equal to or greater than the inner diameter of the outer conductor of the coaxial probe. And it is desirable that the intermediate layer has a configuration in which the outer diameter of the inner conductor and the inner diameter of the outer conductor continuously decrease toward the coaxial probe side, so that the ratio of the outer diameter of the inner conductor to the inner diameter of the outer conductor of the coaxial cable and the ratio of the outer diameter of the inner conductor to the inner diameter of the inner conductor of the coaxial probe can be joined without changing.

[0026] Thus, in the intermediate layer at the connection portion between the coaxial cable and the coaxial probe, since the configuration is such that the ratio of the outer diameter of the inner conductor to the inner diameter of the outer conductor does not change, the characteristic impedance of the intermediate layer does not change or can be minimized.

[0027] Note that the probe card is a tip-side attachment attached to the outer conductor of the coaxial probe. It is desirable to have a configuration including a tip-side attachment having a probe portion whose shape can be changed so that electrical conduction can be established between the ground electrode and the outer conductor of the coaxial probe according to the position of the ground electrode of the object to be inspected.

[0028] By adopting a configuration including a tip-side attachment, even when the intervals between the electrode portions of the measurement object are different (changed), the probe (connection portion) of the tip-side attachment can be bent or curved according to the interval and properly connected.

Advantages of the Invention

[0029] With the configuration as described above, the probe card according to the present invention can achieve some or all of the improvement in reliability and durability, and mass production.

Brief Description of the Drawings

[0030]

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Embodiments for Carrying Out the Invention

[0031] Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention is not limited to the following contents unless the gist thereof is changed. In this description, parts having the same configuration and function are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

[0032] [Manufacturing Process of High-Frequency Device] The manufacturing process of the high-frequency device includes processes such as a pre-process, a wafer test, a post-process, and a product test (see FIG. 1).

[0033] Stating the outline of each process, first, in the pre-process, hundreds to tens of thousands of high-frequency device chips are formed on a wafer (a material for manufacturing high-frequency device elements formed on a disk-shaped plate). Then, a wafer test (electrical characteristic test) is performed on each of the formed high-frequency device chips (hereinafter, sometimes simply referred to as "chips" or "objects to be inspected"), and they are classified into good products and defective products. After that, in the post-process, wiring, resin encapsulation, etc. are performed only on those determined to be good products in the wafer test. Finally, a product test is performed on each of the high-frequency devices on which wiring, resin encapsulation, etc. have been performed, and only those that pass are shipped.

[0034] Therefore, if the quality (accuracy) of wafer testing is poor, problems such as waste of cost and time and inability to achieve production plans will occur in the manufacture of high-frequency devices. For example, if a good product is judged as a defective product in wafer testing, the materials and operations (previous processes) will be wasted. Conversely, if a defective product is judged as a good product in wafer testing, there is a risk that the defective product will be shipped as it is, and post-processes (such as wiring and resin encapsulation) will also be performed on the defective product.

[0035] Thus, in the manufacturing process of high-frequency devices, wafer testing is an important process. Here, FIG. 2 is a schematic configuration diagram showing an example of an apparatus used in wafer testing. Using a probe card 1 disposed on a wafer 90, electrical characteristics tests are performed on each of the chips formed on the wafer 90. More specifically, the test apparatus used in wafer testing includes a tester that performs determination of whether the electrical characteristics are good or bad based on generation / transmission of test signals and the returned operation signals, a test head, and a probe.

[0036] The probe transmits and receives signals to and from the chips on the wafer 90 via the probe card 1. Also, the probe card 1 is for reliably transmitting and receiving the test signals and operation signals transmitted and received between the tester and the chips. That is, the probe card plays a role of accurately transmitting the test signal generated by the tester to the chip, receiving the operation signal of the chip, and accurately transmitting it to the tester. Therefore, it is no exaggeration to say that the quality of wafer testing depends on the probe card, and there is a demand for highly convenient probe cards that can achieve improvements in reliability, durability, and mass production worldwide.

[0037] [Conventional Probe Card] FIG. 3 is a schematic configuration diagram showing an example of a conventional probe card. More specifically, it is a perspective view of the probe card described in Patent Document 1. In the conventional probe card, a connector 81 is provided on the upper part of a printed circuit board 80, and a signal line extending from a tester is connected thereto (see FIG. 2).

[0038] Also, a cable 82 connected to the connector 81 is provided at the lower part of the printed circuit board 80 (in the direction where the wafer 90 is located). The cable 82 is composed of a core and an insulating coating covering the core, and the base end portion of the probe pin 83 is in direct contact with the tip (tip portion) of the core (see FIG. 2 of Patent Document 1). Note that in the conventional probe card, there is one probe pin 83 for the signal line and two probe pins 83 for the ground line, and these respectively contact the signal electrode portion E1 and the ground electrode portions E2 (E21, E22) of the object to be inspected (chip).

[0039] Then, the test signal transmitted from the tester passes through the cable 82 via the connector 81 from the signal line and is transmitted into the chip from the tip portion of the probe pin 83 that contacts the electrode portion of the chip. On the other hand, for the operation signal received from the chip, it follows the reverse route.

[0040] However, in the conventional probe card, since the probe pins for the signal line and the probe pins for the ground line are separated in this way, impedance matching cannot be achieved up to the vicinity of the electrode portion of the chip. Therefore, as described above, it is difficult to use the conventional probe card for electrical inspection and measurement of high-frequency devices used in a high-frequency band of 5G or higher.

[0041] [Probe Card of the Present Invention] FIG. 4 is a schematic configuration diagram showing an example of the probe card of the present invention, and is shown as a partially omitted cross-sectional view. The probe card 1 of the present invention includes a printed circuit board 80 provided with a connector 81 at the upper part, a coaxial cable (semi-rigid cable 70) connected to the connector 81, and a coaxial probe 10 connected to the semi-rigid cable 70. In this description, the coaxial cable used for the probe card 1 will be described as the semi-rigid cable 70.

[0042] The semi-rigid cable 70 is fixed to the electrode plate 40, and the tip of the semi-rigid cable 70 is connected to the base end of the coaxial probe 10. Also, the base end of the coaxial probe 10 is fixed by the base end side plate 41. On the other hand, the tip of the coaxial probe 10 is fixed by the tip side plate 50. And a portion (coaxial probe needle) that contacts the chip on the wafer 90 is provided at the tip of the coaxial probe 10.

[0043] The semi-rigid cable 70 used for the probe card 1 of the present invention also has a coaxial structure composed of an inner conductor 71, an inner insulator 72, an outer conductor 73, and an outer insulating material 74, and the outer conductor 73 electrically shields the inner conductor 71 (see FIGS. 8 and 9(B)).

[0044] Also, in this embodiment, the printed circuit board 80 and the electrode plate 40 are fixed by the support pillar P1. And the base end side plate 41 and the tip side plate 50 are fixed to the electrode plate 40 by the support pillar P2. Note that such a configuration is merely an example and can be appropriately changed in design.

[0045] [Coaxial Probe] The coaxial probe 10 is an elongated rod-shaped body (cylindrical body) as a whole and is a vertical type arranged substantially perpendicular to the inspection object. And the coaxial probe 10 has a coaxial structure except for a part of the base end 10p and a part of the tip end 10t (see FIG. 5).

[0046] Specifically, as shown in FIG. 5, the coaxial probe 10 is composed of an inner conductor 11, an inner insulator 12, and an outer conductor 13 from its center. Further, the outer conductor 13 is covered with an outer insulating material 14. The inner conductor 11 and the outer conductor 13 are made of materials such as rhenium tungsten, palladium alloy, beryllium steel, and other various metals and alloys. On the other hand, the outer insulating material 14 is made of an insulating resin such as polyurethane, polyester, polyesterimide, polyamideimide, polyimide, or fluororesin.

[0047] Further, the inner conductor 11 is a columnar shape with a diameter of 50 μm to 250 μm and an overall length of 10 mm to 30 mm, and the tip 11N (see FIG. 6(B)) of the protruding portion is rounded so as to have a shape such as a semi-sphere, semi-ellipsoid, cone, or truncated cone. On the other hand, the length L2 of the width of the coaxial probe 10 (see FIG. 5(A)) is designed according to the distance between the signal electrode and the ground electrode of the object to be measured, but is generally about 0.5 mm.

[0048] Note that the coaxial probe 10 is configured by a plurality of outer conductors 13 surrounding the inner insulator 12. The outer conductor 13 is an elastically deformable wire made of the above-described material, and the inner conductor 11, the inner insulator 12, and the outer insulating material 14 are also elastically deformable. Therefore, the coaxial probe 10 is elastically deformable as a whole, and by deforming, it can absorb the impact generated when contacting the electrode portion of the object to be measured in the wafer test.

[0049] Further, since the coaxial probe 10 is a rod-shaped body (columnar body), its cross-section is circular. In this embodiment, the inner insulator 12 is provided so as to be surrounded by the outer conductor 13 (see FIG. 5(B)). Here, it is desirable that the plurality of outer conductors 13 be provided without gaps so as to ensure measurement accuracy. Of course, since the diameter of the inner insulator 12 changes when the core diameter (the diameter of the inner conductor 11) changes, the number of outer conductors 13 provided is appropriately designed according to the core diameter.

[0050] Therefore, the coaxial probe tip portion (the portion corresponding to the outer conductor 13 of the present invention) of the probe in the conventional Patent Document 3 or Patent Document 4 is a simple single wire, and that portion did not have a shield structure with respect to the inner conductor 11. In contrast, the outer conductor 13 of the present invention is provided so as to surround the inner conductor 11 via the inner insulator 12 (it has a shield structure). Therefore, it is possible to confine the high-frequency signal flowing through the inner conductor 11 with the outer conductor 13, prevent the high-frequency signal from leaking to the outside, and prevent signal loss and the like. Further, since the outer conductor 13 prevents the intrusion of noise signals such as electromagnetic waves and noise from the outside, the high-frequency signal can be transmitted to the electrode of the measurement object with good quality.

[0051] Note that, as in the present embodiment, by configuring the coaxial probe 10 such that the inner insulator 12 is surrounded by a plurality of outer conductors 13, the pressure applied inside the coaxial probe 10 can be reduced, and the elastic force of the entire coaxial probe 10 can be improved. Therefore, the durability of the coaxial probe 10 can be improved (the number of times it can be used repeatedly can be increased).

[0052] However, when measurement accuracy is emphasized more than durability, the configuration may be such that the outer conductor 13 coats the periphery of the inner insulator 12.

[0053] [Base end side attachment, tip end side attachment] The probe card 1 has a base end side attachment 20 attached to the base end portion 10p of the coaxial probe 10 (see FIG. 6). Further, the probe card 1 has a tip end side attachment 30 attached to the tip end portion 11t of the coaxial probe 10 (see FIG. 6).

[0054] In this embodiment, the base-end side attachment 20 is composed of a main body portion 20A and a plurality of connection portions 20B. The main body portion 20A is formed in a shape that can be fitted onto the base end portion 10p of the coaxial probe 10 so as to be electrically connected to the outer conductor 13 of the coaxial probe 10. In this embodiment, it has a ring shape. For example, the base-end side attachment 20 is fitted onto a portion of the exposed outer conductor 13 that is not covered by the outer insulating material 14 of the coaxial probe 10.

[0055] Further, the connection portion 20B has a function of connecting to the semi-rigid cable 70. More specifically, the connection portion 20B has a function of connecting the outer conductor 13 of the coaxial probe 10 and the outer conductor 73 of the semi-rigid cable 70. In this embodiment, four connection portions (connection portions 20B1 to 20B4) are provided (see FIGS. 6 and 8), but the shape and number are not limited to this.

[0056] Note that, as will be described later with reference to FIG. 13, it is desirable that the base-end side attachment 20 has a structure in which an intermediate layer is provided between the semi-rigid cable 70 and the base end portion of the coaxial probe 10, but it is sufficient that the outer conductor 73 of the semi-rigid cable 70 and the outer conductor 13 of the coaxial probe 10 can be electrically connected. For example, as shown in FIG. 9(B), a structure in which a space S is provided around the inner insulator 12 of the coaxial probe 10 may be used.

[0057] On the other hand, the tip-end side attachment 30 is composed of a main body portion 30A and a plurality of connection portions 30B. The main body portion 30A is formed in a shape that can be fitted onto the tip end portion 10t of the coaxial probe 10 so as to be electrically connected to the outer conductor 13 of the coaxial probe 10. In this embodiment, it has a ring shape. Also, two connection portions (connection portions 30B1 and 30B2) are provided, but the shape and number are not limited to this example. The connection portions 30B1 and 30B2 are provided as probes to be respectively connected to the ground electrode portions E2 (ground electrode portions E21 and E22) of the object to be measured (see FIG. 8). Note that the connection portion 30B can be bent or curved.

[0058] Here, the length L1 of the portion 11N that protrudes from the coaxial structure of the coaxial probe 10 to which the tip-side attachment 30 is attached (the portion that contacts the signal electrode portion of the object to be inspected) is designed according to the thickness of the protective film F provided on the object to be measured (wafer 90) (see FIG. 7). That is, the length L1 is a length obtained by adding a margin for the deflection of the inner conductor 11 and / or the deflection of the outer conductor 13 due to the elasticity of the coaxial probe 10, etc., in addition to the thickness of the protective film F, and is about 30 μm to 1 mm.

[0059] The protective film F may not be on the electrode depending on the type of the object to be inspected, but the general thickness is about 0.5 μm to 5 μm. Also, when the inner conductor 11, the outer conductor 13 of the coaxial probe 10, and the connection portion 30B of the tip-side attachment 30 contact the signal electrode portion E1 and the ground electrode portions E21, E22 (see FIG. 8) of the wafer 90, they bend (as an example, see FIG. 7). In order for the tip portions of the inner conductor 12 and the outer insulator 14 of the coaxial probe 10 not to contact the protective film F due to such bending and to obtain a shielding effect in terms of electrical characteristics, it is desirable that the length L1 is about 30 μm to 1 mm.

[0060] Also, in the present embodiment, the object to be measured formed on the wafer 90 includes one signal electrode portion E1 and two ground electrode portions E21, E22 (see FIG. 8). The inner conductor 11 (the protruding portion 11N) of the coaxial probe 10 contacts the signal electrode portion E1.

[0061] On the other hand, the connection portions 30B1, 30B2 of the tip-side attachment 30 contact the ground electrode portions E21, E22, respectively. In short, the outer conductor 13 (any one of the plurality of outer conductors 13) of the coaxial probe 10 contacts the ground electrode portions E21, E22 of the object to be measured through the connection portions 30B1, 30B2 of the tip-side attachment 30.

[0062] In this embodiment, the distances between the signal electrode portion E1 of the object to be measured and the ground electrode portions E21 and E22 are each 0.25 mm. However, the sizes of the main body portion 30B and the connection portion 30B of the tip-side attachment 30 are also appropriately designed according to the distance. Also, the number of connection portions 30B can be provided in the necessary number according to the number of ground electrode portions of the object to be measured.

[0063] Note that there are multiple types of objects to be measured, and the distances between the electrode portions provided for each type are also different. However, by attaching the tip-side attachment 30 to the tip portion 10t of the coaxial probe 10, even when the type of the object to be measured changes, it is possible to appropriately connect by bending or curving the connection portion 30B according to the distance between the electrode portions.

[0064] Of course, as shown in FIG. 9(A), if the distance between the signal electrode portion E1 of the object to be measured and the ground electrode portions E21 and E22 is substantially the same as the distance between the inner conductor 11 and the outer conductors 13 (outer conductors 131 and 132) at the tip portion 10t of the coaxial probe 10, it is also possible to adopt a configuration in which the tip-side attachment 30 is not attached.

[0065] [Base-end-side plate] Also, the base-end portion 10p of the coaxial probe 10 of the probe card 1 is fixed by the base-end-side plate 41. The base-end-side plate 41 is made of ceramic or engineering plastic resin and is composed of a plurality of plates. For example, in this embodiment, it is configured by laminating three base-end-side plates 411, 412, and 413 (see FIG. 10).

[0066] Note that the base-end-side plates 411, 412, and 413 are provided with through-holes through which the base-end portion 10p of the coaxial probe 10 can be inserted. The diameter of the cross-section of this through-hole is about 1.1 to 1.2 times the diameter of the coaxial probe 10 including the insulating material 14. Also, the shape of the cross-section of this through-hole may be an elliptical shape, a polygonal shape, etc. in addition to a circular shape.

[0067] The base-end side plates 411, 412, and 413 are laminated such that the through-holes provided in each of them are connected while being slightly shifted in the horizontal direction (the left-right direction in FIG. 10). The laminated base-end side plates 411, 412, and 413 are fixed by fixtures 42 such as bolts and screws.

[0068] When the base end 10p of the coaxial probe 10 is inserted into each of the through-holes of the base-end side plates 411, 412, and 413 that are connected while being slightly shifted, the base end 10p of the coaxial probe 10 elastically deforms and bends. Then, the insulating material 14 covering the coaxial probe 10 comes into contact with the corners of the respective through-holes and elastically or plastically deforms so that the corners bite in. Due to this deformation, the coaxial probe 10 is supported by the base-end side plate 41 without falling off.

[0069] In short, the probe card 1 fixes the base end 10p of the coaxial probe 10 to the base-end side plate 41 by utilizing the elastic force of the coaxial probe 10 itself.

[0070] (Example) Subsequently, the configuration of the probe card 1 will be described in more detail, including the problems and examples in the conventional probe card.

[0071] As one of the problems in the conventional probe card, as described at the beginning, there is a problem that it cannot be used because the signal attenuation amount in a high-frequency band of 5G or higher is large. For example, it is desirable that the signal attenuation amount of the probe card is small, and a general standard value is set within -2.0 dB. That is, if the signal attenuation amount exceeds -2.0 dB, it is said that it cannot be used for wafer testing.

[0072] FIG. 11 is a graph showing the measured values of the signal attenuation amount of a conventional probe card obtained from an experiment conducted within Toho Electronics Co., Ltd.

[0073] Here, the length of the portion (the portion that is not in the coaxial structure of the coaxial probe and the unshielded portion of the coaxial probe) of the coaxial probe of the measured conventional probe card that contacts the chip on the wafer 90 is 2.0 mm. As can be seen from this graph, the signal attenuation amount is within the standard value (within -2.0 dB) up to a frequency of about 10 GHz, but when the frequency is higher than 10 GHz, the signal attenuation amount exceeds the standard value. This is because when the length of the portion is long (for example, 2.0 mm as described above), reflection occurs at the exposed portion (the unshielded portion), and the insertion loss and reflection loss deteriorate.

[0074] Therefore, in the conventional probe card, the signal attenuation amount in the high-frequency band of 5G (about 28 GHz) greatly exceeds the standard value, so it cannot be used for wafer testing.

[0075] In response to such problems, the inventors of the present invention have found that when the length of the unshielded portion of the coaxial probe (the length L1 of the portion 11N protruding from the coaxial structure 10 of the coaxial probe shown in FIG. 6(B)) is shortened, the signal attenuation amount can be reduced, and they have succeeded in shortening the length L1.

[0076] The length L1 is designed according to the thickness of the protective film on the electrode of the object to be measured, and the length is the length obtained by adding a margin for the bending of the inner conductor and the outer conductor due to the elasticity of the coaxial probe in addition to the thickness of the protective film, and about 30 μm to 1 mm is desirable.

[0077] Thus, since the probe card 1 of this embodiment has a shield structure (a coaxial path with impedance matching) up to the very tip 10t of the coaxial probe 10, the signal attenuation (loss) amount can be minimized. Therefore, the probe card 1 can be used for wafer testing of high-frequency device chips used in high-frequency bands of 5G or higher.

[0078] Furthermore, as one of the problems in conventional probe cards, there is a problem that the electrical characteristics (impedance) between the semi-rigid cable and the base end portion of the coaxial probe do not meet the standard values. Since the diameter of the semi-rigid cable is different from that of the coaxial probe (the diameter of the semi-rigid cable is larger), it is necessary to join these so that a test signal from a tester (see FIG. 1) and the like can be correctly transmitted.

[0079] For example, the impedance variation at the joint between the base end portion of the coaxial probe and the semi-rigid cable is defined to be "within 50.0 Ω ± 5%", but there are also probe cards that do not meet this condition (for example, Patent Documents 3 and 4).

[0080] One of the causes is that since the base end portion of the coaxial probe and the semi-rigid cable are joined by solder, the impedance varies due to the variation in the volume of the solder.

[0081] Here, the inventors of the present invention conducted research and development on a joint structure that does not use solder and succeeded in realizing it.

[0082] (Joint Configuration 1) FIG. 12(A) is a schematic diagram showing a configuration in which the base end portion of the semi-rigid cable 70 and the coaxial probe 10 are directly joined. It is possible to join the semi-rigid cable 70 and the coaxial probe 10 in this way without using solder. However, in this case, the electric field concentrates on the corner portion of the inner conductor 71 of the semi-rigid cable 70 (see the dotted frame shown in FIG. 12(A)). This is also clear from the result of the electromagnetic field simulation shown in FIG. 12(B), which causes reflection and increases the impedance variation.

[0083] (Joint Configuration 2) Therefore, in the joint configuration shown in Fig. 13(A) (hereinafter referred to as "joint configuration 2"), an intermediate layer is provided between the semi-rigid cable 70 and the base end portion of the coaxial probe 10. This intermediate layer is a layer including an inner conductor, an insulator, and an outer conductor. In the present embodiment, the base end portion side attachment 20 is configured to include an inner conductor 21, an inner insulator 22, and an outer conductor 23.

[0084] Also, in the joint configuration 2, the outer diameter R21 of the inner conductor 21 of the base end portion side attachment 20 on the semi-rigid cable 70 side (the side joined to the semi-rigid cable 70) is equal to or less than the outer diameter R11 of the inner conductor 71 of the semi-rigid cable 70. Further, the inner diameter R22 of the outer conductor 23 of the base end portion side attachment 20 on the semi-rigid cable 70 side is equal to or less than the inner diameter R12 of the outer conductor 73 of the semi-rigid cable 70.

[0085] In addition, in the joint configuration 2, the outer diameter R21 of the inner conductor 21 of the base end portion side attachment 20 on the coaxial probe 10 side (the side connected to the coaxial probe 10) is equal to or greater than the outer diameter R31 of the inner conductor 11 of the coaxial probe 10. Further, the inner diameter R22 of the outer conductor 23 of the outer conductor 13 of the base end portion side attachment 20 on the coaxial probe 10 side is equal to or greater than the inner diameter R32 of the coaxial probe 10.

[0086] Furthermore, in the joint configuration 2, the outer diameter of the inner conductor 21 and the inner diameter of the outer conductor 23 of the base end portion side attachment 20 are not changed between the semi-rigid cable 70 side and the coaxial probe 10 side, and the relationships of "R11 ≧ R21 ≧ R31" and "R12 ≧ R22 ≧ R32" are satisfied.

[0087] (Joint configuration 3) On the other hand, in the joint configuration shown in Fig. 13(B) (hereinafter referred to as "joint configuration 3"), the inner diameter of the outer conductor 23 of the base end side attachment 20 and the inner diameter of the inner conductor 21 of the base end side attachment 20 are changed. Specifically, the inner diameter R221 on the semi-rigid cable 70 side of the outer conductor 23 of the base end side attachment 20 is larger than the inner diameter R222 on the coaxial probe 10 side (R221 > R222). Also, the outer diameter R211 on the semi-rigid cable 70 side of the inner conductor 21 of the base end side attachment 20 is larger than the inner diameter R212 on the coaxial probe 10 side (R211 > R212).

[0088] In short, in joint configuration 3, the outer conductor 23 of the base end side attachment 20 gradually (continuously) decreases in inner diameter from the semi-rigid cable 70 side to the coaxial probe 10 side (is inclined), and the inner conductor 21 of the base end side attachment 20 also gradually (continuously) decreases in outer diameter from the semi-rigid cable 70 side to the coaxial probe 10 side (is inclined).

[0089] And at this time, the ratio of the outer diameter R211 of the inner conductor 21 and the inner diameter R221 of the outer conductor 23 of the base end side attachment 20 and the ratio of the outer diameter R212 of the inner conductor 21 and the inner diameter R222 of the outer conductor 23 are formed so as not to change. In short, "R211:R221" = "R212:R222", and the same applies to the ratio of the outer diameter of the inner conductor 21 and the inner diameter of the outer conductor 23 in the middle.

[0090] That is, joint configuration 3 joins the ratio of the outer diameter R11 of the inner conductor 71 and the inner diameter R12 of the outer conductor 73 of the semi-rigid cable 70 and the ratio of the outer diameter R31 of the inner conductor 11 and the inner diameter R32 of the inner conductor 13 of the coaxial probe 10 so that they do not change even in the middle.

[0091] Regarding these joint configurations 1 to 3, a simulation of the electrical characteristics (reflection loss characteristics) between the semi-rigid cable 70 and the base end of the coaxial probe 10 was performed, and the results were summarized in a graph (see Fig. 14).

[0092] As can be seen from this result, the amount of reflection loss is suppressed more when an intermediate layer is provided (bonding configuration 2, bonding configuration 3) than when directly bonded (bonding configuration 1). Furthermore, the amount of reflection loss is further suppressed when the outer diameter of the inner conductor 21 and the inner diameter of the outer conductor 23 of the base end side attachment 20 are changed (bonding configuration 3).

[0093] Here, the reason why the amount of reflection loss is suppressed in the bonding configuration 3 will be explained. Let the outer diameter of the inner conductor 21 of the base end side attachment 20 be a (mm), the outer diameter of the outer conductor 23 be b (mm), and the relative permittivity of the inner insulator 22 be ε s Then, the characteristic impedance Z0 (Ω) of the coaxial line is obtained by Equation 1.

[0094] Z0 = 138·(ε s )^1 / 2·log(b / a) ··· Equation (1)

[0095] And when there is a step in the impedance of the electrical path, reflection loss occurs at that step and signal loss occurs.

[0096] However, the bonding configuration 3 is configured such that the ratio of the outer diameter of the inner conductor 21 and the inner diameter of the outer conductor 23 of the base end side attachment 20 does not change. Therefore, no impedance step (or the change is minimized) occurs between the semi-rigid cable 70 and the intermediate layer (base end side attachment 20), and between the intermediate layer (base end side attachment 20) and the coaxial probe 10. Therefore, the variation in impedance at the portion where the semi-rigid cable 70 and the base end of the coaxial probe 10 are joined is also minimized, and as a result, the reflection loss is also minimized.

[0097] The probe card 1 described as above is an example of the probe card according to the present invention, and the configuration of the present invention is not limited to the illustrated one as long as it does not depart from the gist of the present invention.

[0098] For example, the configurations of the base-end-side attachment 20 and the tip-end-side attachment 30 are not limited to the configurations of the main body parts 20A and 30A and the connection parts 20B and 30B as illustrated, and can be designed as appropriate. Further, the intermediate layer provided between the semi-rigid cable 70 and the base end of the coaxial probe 10 may be a separate part (separate body) from the base-end-side attachment 20.

Industrial Applicability

[0099] The probe card according to the present invention can be used in the manufacturing process (wafer test) of 5G high-frequency devices, and of course can also be used in the manufacturing processes of 4G high-frequency devices and next-generation (6G and above) high-frequency devices, and thus is industrially useful.

Explanation of Signs

[0100] 1 Probe card 10 Coaxial probe 10p Base end of the coaxial probe 10t Tip end of the coaxial probe 11 Inner conductor 11N Portion protruding from the coaxial structure 12 Inner insulator 13 Outer conductor 14 Outer insulating material 20 Base-end-side attachment 20A Main body part of the base-end-side attachment 20B, 20B1, 20B2, 20B3, 20B4 Connection parts of the base-end-side attachment 21 Inner conductor of the base-end-side attachment 22 Inner insulator of the base-end-side attachment 23 Outer conductor of the base-end-side attachment 30 Tip-end-side attachment 30A Main body part of the tip-end-side attachment 30B, 30B1, 30B2 Connection parts (probes) of the tip-end-side attachment 40 Electrode plate 41 Base-end-side plate 411 Base-end-side plate (first layer) 412 Base-end-side plate (second layer) 413 Base-end-side plate (third layer) 42 Fixture 50 Tip-end-side plate 70 Semi-rigid cable 71 Inner conductor of semi-rigid cable 72 Inner insulator of semi-rigid cable 73 Outer conductor of semi-rigid cable 74 Outer insulating material of semi-rigid cable 80 Printed circuit board 81 Connector 82 Cable 83 Probe pin 90 Wafer E1 Signal electrode part of object to be inspected E2, E21, E22 Ground electrode part of object to be inspected F Protective film P1, P2 Support part L1 Length of part without shield structure L2 Length of width of coaxial probe R11 Outer diameter of inner conductor of semi-rigid cable R12 Inner diameter of outer conductor of semi-rigid cable R21 Outer diameter of inner conductor of base-end-side attachment R211 Outer diameter of inner conductor of base-end-side attachment on semi-rigid cable side R212 Outer diameter of inner conductor of base-end-side attachment on coaxial probe side R22 Inner diameter of outer conductor of base-end-side attachment R221 Inner diameter of outer conductor of base-end-side attachment on semi-rigid cable side R222 Inner diameter of outer conductor of base-end-side attachment on coaxial probe side R31 Outer diameter of inner conductor of coaxial probe R32 Inner diameter of outer conductor of coaxial probe S Space

Claims

1. A probe card for measuring the electrical characteristics of a measurement object, comprising: a coaxial cable to which a test signal is input from the outside; a coaxial probe having flexibility, a proximal end portion of which is connected to the coaxial cable and a distal end portion of which contacts an electrode of the measurement object, wherein at the distal end portion of the coaxial probe, an inner conductor contacts a signal electrode of the measurement object and an outer conductor contacts a ground electrode of the measurement object, wherein when the inner conductor contacts the signal electrode of the measurement object provided with a protective film, the inner conductor is bent, but the tip portions of the inner insulator and the outer insulator do not contact the protective film, and the coaxial structure extends up to immediately before the protective film. The probe card is characterized by this.

2. An intermediate layer provided between the coaxial cable and the coaxial probe, the intermediate layer having an inner conductor and an outer conductor, The probe card according to claim 1, characterized in that the inner conductor and the outer conductor of the intermediate layer are connected to the inner conductor and the outer conductor of the coaxial probe and the inner conductor and the outer conductor of the coaxial cable, respectively.

3. The outer diameter of the inner conductor of the intermediate layer on the coaxial cable side is equal to or less than the outer diameter of the inner conductor of the coaxial cable, and / or the inner diameter of the outer conductor of the intermediate layer on the coaxial cable side is equal to or less than the inner diameter of the outer conductor of the coaxial cable, The outer diameter of the inner conductor of the intermediate layer on the coaxial probe side is equal to or greater than the outer diameter of the inner conductor of the coaxial probe, and / or the inner diameter of the outer conductor of the intermediate layer on the coaxial probe side is equal to or greater than the inner diameter of the outer conductor of the coaxial probe, and the intermediate layer is characterized in that the outer diameter of the inner conductor and the inner diameter of the outer conductor continuously decrease toward the coaxial probe side, so that the ratio of the outer diameter of the inner conductor to the inner diameter of the outer conductor of the coaxial cable and the ratio of the outer diameter of the inner conductor to the inner diameter of the inner conductor of the coaxial probe are joined without change. The probe card according to claim 2.

4. A tip-side attachment attached to the outer conductor of the coaxial probe, The probe card according to any one of claims 1 to 3, further comprising a tip-side attachment having a probe portion whose shape can be changed so that electrical conduction can be established between the ground electrode and the outer conductor of the coaxial probe according to the position of the ground electrode of the inspection object.

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