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 technology]

[0002] In recent years, the development of 5G high-frequency devices has been progressing in the field of high-speed communications such as smartphones, with the commercial launch of 5G (fifth-generation mobile communications system) in 2020. In line with this, the development of probe cards required for testing the electrical characteristics of high-frequency devices (high-frequency device chips) used at 5G frequencies is also progressing.

[0003] 5G high-frequency devices will support a variety of fields, including smart industry, logistics, construction, agriculture, health and medicine, education, and remote offices, and mass production of probe cards is required. At the same time, probe cards are also required to be reliable, such as reducing signal attenuation and impedance variations during wafer testing, as well as durable.

[0004] Here, Patent Documents 1 to 4 show prior art related to probe cards. Patent Document 1 describes a probe card capable of improving the measurement accuracy of electrical characteristics. Specifically, the probe card 100 includes a probe pin 10 made of a metal conductor and elastically deformable, with a tip 11 protruding from an end face 72A, and a cable 30 having a core 31 made of an electric conductor electrically connected to the probe pin 10 and an inspection device, and an insulating coating 32 made of an insulator that covers the core 31 (see FIG. 1). In the probe card 100, the base end 11 of the probe pin 10 and the tip end of the core 31 are in direct contact with each other.

[0005] Furthermore, Patent Document 2 states: measurementThe document describes a probe card equipped with a vertical probe needle that can prevent a decrease in contact stability with an object and can be used repeatedly for a long period of time. Specifically, the vertical probe needle is made of a thin metal wire 1 having a diameter of 0.02 to 0.04 mm and a length of 3.0 to 6.0 mm, with a body 1b covered with an insulating coating 2 of SiO2 and a tip 1a on which a metal coating 3 having granular protrusions 3a is formed. The edge 2a of the insulating coating 2 is located 20 to 60 μm from the apex 5, and the apex 5 is formed in an arc shape with a radius of curvature of 26 to 45 μm in vertical cross section (see FIG. 1).

[0006] Patent Document 3 describes a probe card using a probe that aims to maintain electrical isolation of the probe and ensure impedance matching of the needles, thereby improving the accuracy of high-frequency electrical characteristic testing. Specifically, the document describes a probe 1 that includes 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). Furthermore, the probe 1 includes a connecting conductor 6 that connects the auxiliary conductor 4 and the second probe 5.

[0007] Furthermore, Patent Document 4 describes a coaxial probe that aims to suppress impedance fluctuations even when the distance between the signal pad and the ground pad of the device under test is different 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 alongside the signal terminal 124, and an attachment signal conductor 13 having a cylindrical structure with a hole 131 into which the signal terminal 124 can be inserted, and which is attached to and electrically connected to the signal terminal 124 (see FIG. 4). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication 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 [Problem to be solved by the invention]

[0009] However, in the probe card described in Patent Document 1, the base end of the probe pin and the tip end of the core of the cable are in direct contact with each other, and therefore, deterioration of the electrical signal obtained through the probe pin can be suppressed compared to when the probe pin and the core of the cable are connected via an intervening member such as a connector, a soldered portion, or a coaxial pin, which has poor transmission loss at high frequencies. measurement Although it is possible to improve the accuracy of measuring the electrical characteristics of the target object, such as a chip on a semiconductor wafer, it is not possible to improve the accuracy of measuring the electrical characteristics any further.

[0010] This is because the probe structure disclosed in Patent Document 1 consists only of a conductive probe pin and an insulating coating, and does not have a shielding 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 range. Therefore, the structure in Patent Document 1 does not provide a shielding effect that prevents signal loss and the like in the high-frequency range (the effect of protecting internal signals from interference from external signals and the effect of preventing internal signals from leaking to the outside), thereby making it impossible to improve the accuracy of measuring electrical characteristics.

[0011] The probe card (vertical probe needle) described in Patent Document 2 also has a metal coating having granular protrusions 3a formed on the tip 1a of the probe needle. measurementThis prevents a decrease in contact stability with the object and allows for repeated use over long periods of time, but the structure of the probe needle is the same as in Patent Document 1, consisting of a thin metal wire surrounded by an insulating coating (it is not a shielded structure), so it is not effective against signal loss in the high frequency range.

[0012] On the other hand, the probe card described in Patent Document 3 is provided with an auxiliary conductor that is electrically connected to the external conductor of the probe card and that is arranged 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, and to improve the accuracy of high-frequency electrical characteristic testing. Furthermore, as an effect of this, it is described that an increase in impedance can be suppressed and noise can be reduced by 10 to 20 dB as shown in Figure 14.

[0013] However, while there is a shielding effect only in the area where the auxiliary conductor is located around the inner conductor, there is no auxiliary dielectric in other directions, and so no shielding effect can be obtained. This is clearly evident from the difference of 3 Ω from the coaxial section, as shown in Figure 14.

[0014] Furthermore, Figure 14 of Patent Document 3 shows that when an auxiliary conductor is provided, noise is reduced by 10 to 20 dB compared to when no auxiliary conductor is provided, but the measurement frequency is 10 MHz to 6 GHz, which is lower than the frequency of 5G. It is a well-known fact that noise increases as the frequency increases, so while this may be sufficient in this frequency band, it cannot be said that this structure can sufficiently reduce noise in high-frequency bands above 5G.

[0015] Furthermore, the coaxial probe described in Patent Document 4 is equipped with 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 alongside the signal terminal 124, and an attachment signal conductor 13 which is attached to and electrically connected to the signal terminal 124, in order to suppress impedance fluctuations and obtain sufficient resolution 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.

[0016] As described above, the ground terminal 125 of the coaxial probe described in Patent Document 4 is simply linear and does not have a coaxial structure surrounding the signal terminal 124 that can prevent leakage of high-frequency signals, and therefore cannot prevent signal loss in high-frequency bands of 5G or higher.

[0017] Specifically, as shown in FIG. 5(a), the transmission characteristic after the improvement (corresponding to the insertion loss described later) is −4 dB at 20 GHz, which is merely comparable to the performance of the prior art. Furthermore, as shown in FIG. 5(b), the impedance after improvement is also about 55 Ω.

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

[0019] Therefore, there is a demand for a probe card that can improve on at least one of these standards. In light of the above-mentioned background, there is a demand for probe cards to be more convenient, including being able to improve reliability and durability and being able to be mass-produced.

[0020] Therefore, an object of the present invention is to provide a highly convenient probe card that can achieve some or all of the improvements 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 electrical characteristics of a measurement object, a coaxial cable to which a test signal is input from outside; a flexible coaxial probe having a base end connected to the coaxial cable and a tip end contacting an electrode of the object to be measured; The tip of the coaxial probe has an inner conductor that contacts the signal electrode of the object being measured, and an outer conductor that contacts the ground electrode of the object being measured. When the internal conductor of a coaxial probe contacts a signal electrode of a measurement object that has a protective film provided thereon, even if the internal conductor bends, the tip portions of the internal insulator and external insulator do not come into contact with the protective film, and the coaxial structure extends up to just before the protective film.

[0022] The probe card according to the present invention has such a configuration that the coaxial probe does not damage the protective film of the object to be measured, thereby reducing insertion loss to the greatest extent possible.

[0023] The probe card is an intermediate layer provided between the coaxial cable and the coaxial probe, and includes an inner conductor and an outer conductor; It is desirable that the inner and outer conductors of the intermediate layer are configured to connect to the inner and outer conductors of the coaxial probe and the inner and outer conductors of the coaxial cable, respectively.

[0024] In this way, 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 changes in the characteristic impedance of the connection 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 smaller 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 smaller 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 larger 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 larger than the inner diameter of the outer conductor of the coaxial probe, Furthermore, it is desirable that the intermediate layer be configured so that the outer diameter of the inner conductor and the inner diameter of the outer conductor are continuously reduced toward the coaxial probe side, thereby allowing the joint to be performed without changing the ratio between the outer diameter of the inner conductor of the coaxial cable and the inner diameter of the outer conductor of the coaxial probe.

[0026] In this way, the intermediate layer at the connection point between the coaxial cable and the coaxial probe is configured so that the ratio of the outer diameter of the inner conductor to the inner diameter of the outer conductor does not change, so the characteristic impedance of the intermediate layer does not change or changes can be minimized.

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

[0028] By configuring the device with a tip-side attachment, even if the spacing between the electrodes of the object to be measured differs (changes), the probe (connection part) of the tip-side attachment can be bent or curved according to the spacing to ensure an appropriate connection. [Effects of the Invention]

[0029] With the above-described configuration, the probe card according to the present invention can achieve some or all of improved reliability and durability, and mass production. [Brief explanation of the drawings]

[0030] [Figure 1] 1A to 1C are diagrams for explaining a manufacturing process of a high-frequency device. [Figure 2] FIG. 1 is a schematic diagram illustrating an example of an apparatus used in a wafer test. [Figure 3] FIG. 1 is a schematic diagram illustrating an example of a conventional probe card. [Figure 4] 1 is a schematic diagram illustrating an example of a probe card according to the present invention. [Figure 5] (A) is a schematic vertical cross-sectional view of the coaxial probe, and (B) is a VV cross-sectional view of (A). [Figure 6] (A) is an image showing the state before the base end attachment and the tip end attachment are attached to the coaxial probe, and (B) is an image showing the state after the base end attachment and the tip end attachment are attached to the coaxial probe. [Figure 7] FIG. 1 is an image diagram showing the deflection of the tip of a coaxial probe (inner conductor). [Figure 8] 10 is a schematic diagram for explaining a connection configuration between a coaxial probe having an end-side attachment and a tip-side attachment attached thereto, a semi-rigid cable, and an object to be measured. FIG. [Figure 9] (A) is an image showing the state where the tip of the coaxial probe is in contact with the object to be measured, and (B) is an image showing the state where the base end of the coaxial probe is joined to the semi-rigid cable by the base end attachment. [Figure 10] 10A and 10B are diagrams for explaining the configuration of a base end side plate. [Figure 11] 10A and 10B are diagrams for explaining the relationship between frequency and signal attenuation in a conventional probe card. [Figure 12] 1A and 1B are diagrams for explaining the joint configuration between a semi-rigid cable and the base end of a coaxial probe, in which (A) is a schematic diagram of the joint configuration, and (B) is a diagram showing the results of an electromagnetic field simulation for the joint configuration shown in (A). [Figure 13] 10 is a schematic diagram for explaining a joint configuration between a semi-rigid cable and a base end portion of a coaxial probe. FIG. [Figure 14] FIG. 10 is a diagram showing the simulation results of the electrical characteristics (reflection loss characteristics) between the semi-rigid cable and the base end of the coaxial probe in each joint configuration. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following describes in detail an embodiment of the present invention, but the description of the components described below is one example (typical example) of an embodiment of the present invention, and the present invention is not limited to the following content unless the gist of the present invention is changed. In this description, parts having the same configuration or function are given the same reference numerals in the drawings, and detailed description thereof will be omitted.

[0032] [High frequency device manufacturing process] The manufacturing process for high-frequency devices includes front-end processing, wafer testing, back-end processing, and product testing (see Figure 1).

[0033] To give an overview of each process, first, in the pre-process, high frequency device chips are formed in the hundreds to tens of thousands on a wafer (a material for manufacturing high frequency device elements formed on a disc-shaped plate). Then, these formed high frequency device chips (hereinafter simply referred to as "chips" or " measurement Each of the devices (sometimes called "objects") undergoes a wafer test (a test of electrical characteristics) to separate them into good and bad products. After that, in the post-process, only those that are judged to be good in the wafer test undergo wiring and resin encapsulation. Finally, each high-frequency device that has undergone wiring and resin encapsulation undergoes a product test, and only those that pass are shipped.

[0034] Therefore, if the quality (accuracy) of the wafer test is poor, problems such as cost and time waste and failure to achieve production plans will occur in the manufacture of high frequency devices. For example, if a good product is judged to be defective in wafer testing, materials and work (upfront process) will be wasted. Conversely, if a defective product is judged to be good in wafer testing, there is a risk that the defective product will be shipped as is, and the defective product will also be subjected to downstream processes (wiring, resin encapsulation, etc.).

[0035] Thus, wafer testing is an important step in the manufacturing process of high frequency devices. 2 is a schematic diagram showing an example of an apparatus used in wafer testing, in which a probe card 1 placed on a wafer 90 is used to test the electrical characteristics of each chip formed on the wafer 90. More specifically, the test apparatus used in wafer testing is made up of a tester that generates and transmits test signals and judges the pass / fail of electrical characteristics based on returned operation signals, a test head, and a prober.

[0036] The prober transmits and receives signals to and from chips on the wafer 90 via the probe card 1. The probe card 1 also ensures that test signals and operation signals are transmitted and received reliably between the tester and the chips. In other words, the probe card's role is to accurately transmit test signals generated by the tester to the chip, and also to receive the chip's operating signals and accurately transmit them to the tester. For this reason, it is no exaggeration to say that the quality of wafer testing depends on the probe card, and there is a global demand for highly convenient probe cards that offer improved reliability and durability, and that can be used in mass production.

[0037] [Conventional probe card] Fig. 3 is a schematic 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. The conventional probe card has a connector 81 provided on the top of a printed circuit board 80, to which a signal line extending from a tester is connected (see Fig. 2).

[0038] Further, a cable 82 connected to a connector 81 is provided on the lower side of the printed circuit board 80 (on the side where the wafer 90 is located). The cable 82 is composed of a core and an insulating coating that covers the core, and the base end of the probe pin 83 is in direct contact with the tip (tip) of the core (see FIG. 2 of Patent Document 1). Note that a conventional probe card has one signal line probe pin 83 and two ground line probe pins 83, and these are measurement The signal electrode E1 and the ground electrode E2 (E21, E22) of the target object (chip) are brought into contact with each other.

[0039] The test signal sent from the tester travels from the signal line through connector 81, through cable 82, and into the chip from the tip of probe pin 83 that contacts the electrode of the chip. Meanwhile, the operation signal received from the chip follows the reverse route.

[0040] However, in conventional probe cards, the signal line probe pins and ground line probe pins are separated, so impedance matching cannot be achieved up to the electrodes on the chip. As mentioned above, this makes it difficult to use conventional probe cards for electrical testing and measurement of high-frequency devices used in high-frequency bands above 5G.

[0041] [Probe card of the present invention] 4 is a schematic diagram showing an example of the probe card of the present invention, shown in a partially omitted cross section. The probe card 1 of the present invention includes a printed circuit board 80 having a connector 81 provided on the top thereof, 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 in 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. The base end of the coaxial probe 10 is fixed by a base end side plate 41. On the other hand, the tip of the coaxial probe 10 is fixed by a tip end side plate 50. The tip of the coaxial probe 10 is provided with a portion (coaxial probe needle) that comes into contact with a chip on the wafer 90.

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

[0044] In this embodiment, the printed circuit board 80 and the electrode plate 40 are fixed by a support P1. The base end side plate 41 and the tip end side plate 50 are fixed to the electrode plate 40 by a support P2. Note that this configuration is merely an example, and the design can be modified as appropriate.

[0045] [Coaxial probe] The coaxial probe 10 is an elongated, linear rod-like body (cylindrical body) as a whole. measurement The coaxial probe 10 is a vertical type that is disposed substantially perpendicular to the object, and 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 Figure 5, coaxial probe 10 is composed of, from its center, inner conductor 11, inner insulator 12, and outer conductor 13. Furthermore, outer conductor 13 is covered with outer insulating material 14. Inner conductor 11 and outer conductor 13 are made of materials such as rhenium-tungsten, palladium alloy, beryllium steel, and various other metals and alloys. On the other hand, outer insulating material 14 is made of insulating resin such as polyurethane, polyester, polyesterimide, polyamideimide, polyimide, or fluororesin.

[0047] The inner conductor 11 is cylindrical with a diameter of 50 μm to 250 μm and a total length of 10 mm to 30 mm, and the tip 11N of the protruding portion (see FIG. 6(B)) is rounded to have a semi-spherical, semi-elliptical, conical, truncated conical, etc. Meanwhile, the width L2 of the coaxial probe 10 (see FIG. 5(A)) is designed depending on the distance between the signal electrode and the ground electrode of the object to be measured, but is generally about 0.5 mm.

[0048] The coaxial probe 10 is configured by multiple outer conductors 13 surrounding an inner insulator 12. The outer conductors 13 are elastically deformable wires made of the above-mentioned material, and the inner conductors 11, inner insulators 12, and outer insulators 14 are also elastically deformable. Therefore, the coaxial probe 10 as a whole is elastically deformable, and by deforming, it is possible to absorb the impact that occurs when it comes into contact with the electrode portion of the measurement object during wafer testing.

[0049] Furthermore, since the coaxial probe 10 is a rod-shaped body (cylindrical body), its cross section is circular. In this embodiment, the outer conductor 13 is provided so as to surround the internal insulator 12 (see FIG. 5(B)). Here, it is desirable that the multiple external conductors 13 are provided without any gaps so as to ensure measurement accuracy. Of course, since the diameter of the internal insulator 12 changes when the core diameter (diameter of the internal conductor 11) changes, the number of external conductors 13 to be provided is designed appropriately depending on the core diameter.

[0050] Therefore, the tip portion of the coaxial probe (corresponding to the outer conductor 13 of the present invention) of the conventional probes of Patent Document 3 or Patent Document 4 is a simple single conducting wire, and this portion does not have a shielding structure for the inner conductor 11, whereas the outer conductor 13 of the present invention is provided so as to surround the periphery of the inner conductor 11 via the inner insulator 12 (providing a shielding structure). This makes it possible to confine the high-frequency signal flowing through the inner conductor 11 with the outer conductor 13, preventing the high-frequency signal from leaking to the outside and preventing signal loss, etc. Furthermore, because the outer conductor 13 prevents the intrusion of noise signals such as external electromagnetic waves and noise from entering, the high-frequency signal can be transmitted to the electrode of the measurement object with good quality.

[0051] In addition, by configuring the coaxial probe 10 in such a manner that the inner insulator 12 is surrounded by a plurality of outer conductors 13 as in this embodiment, it is possible to reduce the pressure applied to the inside of the coaxial probe 10 and improve the elasticity of the entire coaxial probe 10. This improves the durability of the coaxial probe 10 (the number of times it can be used repeatedly can be increased).

[0052] However, if measurement accuracy is more important than durability, the periphery of the inner insulator 12 may be coated with the outer conductor 13 .

[0053] [Base end attachment, tip end attachment] In the probe card 1, a base end side attachment 20 is attached to the base end 10p of the coaxial probe 10 (see FIG. 6). In addition, in the probe card 1, a tip end side attachment 30 is attached to the tip end 11t of the coaxial probe 10 (see FIG. 6).

[0054] In this embodiment, the proximal end side attachment 20 is composed of a main body 20A and a plurality of connection portions 20B. The main body 20A is formed in a shape that allows it to be fitted into the proximal end 10p of the coaxial probe 10 so as to establish electrical continuity with the outer conductor 13 of the coaxial probe 10, and in this embodiment, is ring-shaped. For example, the proximal end side attachment 20 is fitted into the exposed portion of the outer conductor 13 of the coaxial probe 10 that is not covered by the outer insulating material 14.

[0055] Furthermore, the connection portion 20B has a function of coupling 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 to the outer conductor 73 of the semi-rigid cable 70, and in this embodiment, four connection portions 20B (connection portions 20B1 to 20B4) are provided (see FIGS. 6 and 8), but the shape and number are not limited to these.

[0056] 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 of the coaxial probe 10, but it is sufficient if it can provide electrical continuity between the outer conductor 73 of the semi-rigid cable 70 and the outer conductor 13 of the coaxial probe 10. For example, as shown in FIG. 9(B), a structure in which a space S is provided around the internal insulator 12 of the coaxial probe 10 may also be used.

[0057] Meanwhile, the tip end attachment 30 is composed of a main body 30A and multiple connection portions 30B. The main body 30A is formed in a shape that allows it to be fitted into the tip end 10t of the coaxial probe 10 so as to establish electrical continuity with the outer conductor 13 of the coaxial probe 10, and in this embodiment, is ring-shaped. Although two connection portions 30B (connection portions 30B1 and 30B2) are provided, the shape and number are not limited to this example, and the connection portions 30B1 and 30B2 are provided so as to function as probes that are respectively connected to the ground electrode portion E2 (ground electrodes E21 and E22) of the measurement object (see FIG. 8). The connection portions 30B can be bent or curved.

[0058] Here, the part of the coaxial probe 10 to which the tip end attachment 30 is attached ( measurement The length L1 of the portion 11N that contacts the signal electrode portion of the object is designed based on the thickness (see FIG. 7) of the protective film F provided on the object to be measured (wafer 90). That is, the length L1 is the thickness of the protective film F plus a margin for bending of the inner conductor 11 and / or the outer conductor 13 due to the elasticity of the coaxial probe 10, and is approximately 30 μm to 1 mm.

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

[0060] In this embodiment, the measurement object formed on the wafer 90 includes one signal electrode portion E1 and two ground electrodes E21 and E22 (see FIG. 8). The signal electrode portion E1 is in contact with the inner conductor 11 (protruding portion 11N) of the coaxial probe 10.

[0061] Meanwhile, the ground electrodes E21 and E22 are in contact with the connecting portions 30B1 and 30B2 of the tip end attachment 30, respectively. In other words, the outer conductor 13 (any of the multiple outer conductors 13) of the coaxial probe 10 is in contact with the ground electrodes E21 and E22 of the object to be measured via the connecting portions 30B1 and 30B2 of the tip end attachment 30.

[0062] In this embodiment, the distance between the signal electrode E1 and the ground electrodes E21, E22 of the object to be measured is 0.25 mm, but the sizes of the main body 30B and the connection part 30B of the tip end attachment 30 are also designed appropriately according to this distance. Also, the number of connection parts 30B can be as many as necessary depending on the number of ground electrodes of the object to be measured.

[0063] There are multiple types of measurement objects, and the spacing between the electrodes varies depending on the type. However, by attaching the tip end attachment 30 to the tip end 10t of the coaxial probe 10, even if the type of measurement object changes, the connection part 30B can be bent or curved according to the spacing between the electrodes, allowing for appropriate connection.

[0064] Of course, as shown in Figure 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 approximately the same as the distance between the inner conductor 11 and the outer conductor 13 (outer conductors 131 and 132) at the tip portion 10t of the coaxial probe 10, the configuration can be such that the tip side attachment 30 is not attached.

[0065] [Base end plate] The base end portions 10p of the coaxial probes 10 of the probe card 1 are fixed by a 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, the base end side plate 41 is composed of three base end side plates 411, 412, and 413 stacked one on top of the other (see FIG. 10).

[0066] The base end side plates 411, 412, and 413 are provided with through holes through which the base end 10p of the coaxial probe 10 can be inserted. The diameter of the cross section of the through holes is approximately 1.1 to 1.2 times the diameter of the coaxial probe 10 including the insulating material 14. The cross section of the through holes may be circular, elliptical, polygonal, or the like.

[0067] The base end side plates 411, 412, and 413 are stacked so that the through holes formed in each are connected while being slightly shifted in the horizontal direction (the left-right direction in FIG. 10). The stacked base end side plates 411, 412, and 413 are fixed with fixing devices 42 such as bolts and screws.

[0068] As a result, when the base end 10p of the coaxial probe 10 is inserted through each of the through-holes of the base end side plates 411, 412, and 413, which are connected while being slightly offset from each other, the base end 10p of the coaxial probe 10 is elastically deformed and bent. Then, the insulating material 14 covering the coaxial probe 10 comes into contact with the corners of each through-hole and elastically or plastically deforms so that the corners bite into them. Due to this deformation, the coaxial probe 10 is supported by the base end side plate 41 without slipping 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) Next, the configuration of the probe card 1 will be described in more detail, including problems with conventional probe cards and examples.

[0071] As mentioned at the beginning, one of the issues with conventional probe cards is that they cannot be used in high-frequency bands above 5G due to their large signal attenuation. For example, it is desirable for a probe card to have low signal attenuation, with the general standard value being set at within -2.0 dB. In other words, if the signal attenuation exceeds -2.0 dB, the card cannot be used for wafer testing.

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

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

[0074] Therefore, conventional probe cards cannot be used for wafer testing because the signal attenuation in the 5G high-frequency band (approximately 28 GHz) significantly exceeds the standard value.

[0075] To address this issue, the inventors of the present invention discovered that the amount of signal attenuation can be reduced by shortening 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 Figure 6(B)), and succeeded in shortening the length L1.

[0076] The length L1 is designed based on the thickness of the protective film on the electrode of the object to be measured, and this length includes the thickness of the protective film as well as a margin for bending of the inner and outer conductors due to the elasticity of the coaxial probe, and is preferably approximately 30 μm to 1 mm.

[0077] In this way, the probe card 1 of this embodiment has a shield structure (coaxial path with impedance matching) right up to the tip 10t of the coaxial probe 10, so that the amount of signal attenuation (loss) 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, one of the issues with conventional probe cards is that the electrical characteristics (impedance) between the semi-rigid cable and the base end of the coaxial probe do not meet the standard values. Because the diameter of the semi-rigid cable and the diameter of the coaxial probe are different (the diameter of the semi-rigid cable is larger), it is necessary to join them so that test signals from the tester (see Figure 1) can be transmitted correctly.

[0079] For example, the standard stipulates that the impedance variation at the joint between the base end of a coaxial probe and a semi-rigid cable must be within 50.0 Ω ±5%, but there are probe cards that do not meet this condition (e.g., Patent Documents 3 and 4).

[0080] One of the reasons for this is that the base end of the coaxial probe and the semi-rigid cable are joined by solder, and the variation in the volume of the solder causes the variation in impedance.

[0081] The inventors of the present invention have therefore carried out research and development into a joining structure that does not use solder, and have succeeded in realizing it.

[0082] (Joint configuration 1) Fig. 12(A) is a schematic diagram showing a configuration in which the base end of the coaxial probe 10 is directly joined to the semi-rigid cable 70. While it is possible to join the semi-rigid cable 70 and the coaxial probe 10 in this manner without using solder, in this case the electric field will concentrate at the corners of the inner conductor 71 of the semi-rigid cable 70 (see the dotted line frame in Fig. 12(A)). This is clear from the results of the electromagnetic field simulation shown in Fig. 12(B), which causes reflections and large variations in impedance.

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

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

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

[0086] Furthermore, in joint configuration 2, 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 not changed between the semi-rigid cable 70 side and the coaxial probe 10 side, and the relationships are "R11≧R21≧R31" and "R12≧R22≧R32".

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

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

[0089] In this case, the ratio between the outer diameter R211 of the inner conductor 21 of the base end side attachment 20 and the inner diameter R221 of the outer conductor 23 and the ratio between 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 other words, "R211:R221" = "R212:R222", and the same applies to the ratio between the outer diameter of the inner conductor 21 and the inner diameter of the outer conductor 23 in between.

[0090] In other words, joint configuration 3 joins the semi-rigid cable 70 so that the ratio between the outer diameter R11 of the inner conductor 71 and the inner diameter R12 of the outer conductor 73 and the ratio between the outer diameter R31 of the inner conductor 11 and the inner diameter R32 of the inner conductor 13 of the coaxial probe 10 do not change along the way.

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

[0092] As can be seen from these results, the amount of return loss is reduced when an intermediate layer is provided (joint configurations 2 and 3) compared to when the connection is direct (joint configuration 1). Furthermore, the amount of return loss is further reduced when the outer diameter of the inner conductor 21 of the base end side attachment 20 or the inner diameter of the outer conductor 23 is changed (joint configuration 3).

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

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

[0095] If there is a step in the impedance of the electrical path, a reflection loss occurs at the step, resulting in a loss of signal.

[0096] However, in joint configuration 3, the ratio between the outer diameter of inner conductor 21 of proximal end attachment 20 and the inner diameter of outer conductor 23 remains unchanged, and therefore no step in impedance occurs (or the change is minimized) between semi-rigid cable 70 and the intermediate layer (proximal end attachment 20), and between the intermediate layer (proximal end attachment 20) and coaxial probe 10. Therefore, the variation in impedance at the joint between semi-rigid cable 70 and the proximal end of coaxial probe 10 is minimized, and as a result, the reflection loss is also minimized.

[0097] The probe card 1 described 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 example provided that it does not deviate from the spirit of the present invention.

[0098] For example, the configurations of the proximal end attachment 20 and the distal end attachment 30 are not limited to the configurations of the main body portions 20A, 30A and the connecting portions 20B, 30B as exemplified, and can be designed as appropriate. Also, the intermediate layer provided between the semi-rigid cable 70 and the proximal end of the coaxial probe 10 may be a separate part (a separate body) from the proximal end attachment 20. [Industrial Applicability]

[0099] The probe card of the present invention can be used in the manufacturing process (wafer testing) of 5G high-frequency devices, and of course can also be used in the manufacturing process of 4G high-frequency devices and next-generation (6G or higher) high-frequency devices, making it industrially useful. [Explanation of symbols]

[0100] 1 probe card 10 Coaxial Probes 10p Coaxial probe base 10t Coaxial Probe Tip 11 Inner conductor 11N Parts protruding from the coaxial structure 12 Inner insulator 13 Outer conductor 14 External insulation 20 Base end attachment 20A Main body of the base end attachment 20B, 20B1, 20B2, 20B3, 20B4 Connection part of base end side attachment 21 Inner conductor of base end attachment 22 Internal insulator of base end attachment 23 Outer conductor of base end attachment 30 Tip side attachment 30A Main body of the tip attachment 30B, 30B1, 30B2 Connection part of tip side attachment (probe) 40 electrode plates 41 Base end side plate 411 Base end plate (1st layer) 412 Base end plate (2nd layer) 413 Base end plate (3rd layer) 42 Fixtures 50 Tip side plate 70 semi-rigid cable 71 Inner conductor of semi-rigid cable 72 Inner insulation of semi-rigid cable 73 Outer conductor of semi-rigid cable 74 Outer insulation of semi-rigid cables 80 Printed Circuit Board 81 Connector 82 Cable 83 probe pin 90 wafers E1 measurement Signal electrode part of the target E2, E21, E22 measurement Ground electrode of the target object F Protective film P1,P2 Support section L1 Length of the part that is not shielded L2 Width of the coaxial probe R11 Outside diameter of the inner conductor of a semi-rigid cable R12 Inner diameter of outer conductor of semi-rigid cable R21 Outer diameter of the inner conductor of the base end attachment R211 Outer diameter of the inner conductor of the base end attachment on the semi-rigid cable side R212 Outer diameter of the inner conductor of the base end attachment on the coaxial probe side R22 Inner diameter of outer conductor of base end attachment R221 Inner diameter of the semi-rigid cable side of the outer conductor of the base end attachment R222 Inner diameter of the outer conductor of the base end attachment on the coaxial probe side R31 Outer diameter of the inner conductor of the coaxial probe R32 Inner diameter of the outer conductor of the coaxial probe S space

Claims

[Claim 1] A probe card for measuring high frequency electrical characteristics of a measurement object, a coaxial cable into which a high frequency test signal is input from outside; a flexible coaxial probe having a base end connected to the coaxial cable and a tip end in contact with an electrode of the measurement object, The tip of the coaxial probe has an inner conductor that contacts a signal electrode of the object to be measured and an outer conductor that contacts a ground electrode of the object to be measured, an intermediate layer provided between the coaxial cable and the coaxial probe, the intermediate layer including an inner conductor and an outer conductor; 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; an outer diameter of the inner conductor of the intermediate layer on the coaxial cable side is equal to or smaller than the outer diameter of the inner conductor of the coaxial cable, and / or an inner diameter of the outer conductor of the intermediate layer on the coaxial cable side is equal to or smaller than the inner diameter of the outer conductor of the coaxial cable, an outer diameter of the inner conductor of the intermediate layer on the coaxial probe side is equal to or larger than an outer diameter of the inner conductor of the coaxial probe, and / or an inner diameter of the outer conductor of the intermediate layer on the coaxial probe side is equal to or larger than an inner diameter of the outer conductor of the coaxial probe, and the intermediate layer has an outer diameter of the inner conductor and an inner diameter of the outer conductor that continuously decrease toward the coaxial probe side, thereby allowing the coaxial cable to be joined without changing the ratio between the outer diameter of the inner conductor and the inner diameter of the outer conductor of the coaxial probe and the ratio between the outer diameter of the inner conductor and the inner diameter of the inner conductor of the coaxial probe.

Images