JP2010122139A - High-frequency probe card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily absorb impedance deviations of cantilevers by simply and appropriately matching the impedance of the cantilevers of a high-frequency probe card to that of a coaxial cable. <P>SOLUTION: Impedance matching is made by connecting variable impedance matching circuits 2 to the cantilevers 3, the matching circuits 2 each being a π matching circuit composed of two trimmer capacitors and a multilayer inductor. Coaxial cables 5 are connected to a tester 4, with the coaxial cables 5 joined to coaxial connectors 6 connected to the matching circuits 2. Measurement is carried out with the cantilevers 3 kept in contact with a pad for inspection of an inspected device 7. Impedance deviations of a probe card 1 in a manufacturing stage can be absorbed by individual adjustment, the probe card 1 being of a high-frequency cantilever-type for inspection on the wafer level. Therefore, a low-cost cantilever-type probe card 1 can be used even for high frequencies. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-frequency probe card, and more particularly to a high-frequency probe card in which a variable impedance matching circuit is provided between a cantilever and a coaxial cable.

  Conventionally, a probe card has been used to measure and inspect the electrical characteristics of each circuit such as a semiconductor wafer and an IC bare chip at the wafer level at the manufacturing process or at the time of acceptance. A probe card has a probe connected to an electrode (bonding pad or inspection pad) of an integrated circuit. Signals are transmitted to and received from each circuit via the probe. A test signal is sent from an external tester to the device under test, and signals received from each circuit of the device under test are sent to the external tester. Even without soldering, the tester can be connected to the device under test relatively reliably.

  The probe of the probe card includes a cantilever type, a coaxial probe type, a blade type, and a vertical probe type. In the cantilever type, the cantilever probe held obliquely is brought into contact with the electrode. In the coaxial probe type, a probe attached to the tip of a coaxial cable type probe support is brought into contact with the electrode. In the blade type, a probe attached to a blade-like support plate is brought into contact with the electrode. In the vertical probe type, the probe held vertically is brought into contact with the electrode vertically. The cantilever type has a simple structure and can be manufactured at low cost. The coaxial probe type is suitable for inspection of high-frequency devices. In the inspection of a high-frequency device, it is necessary to prevent as much noise as possible and to prevent impedance mismatch. For example, a coaxial probe type probe is connected to a tester via a coaxial cable to transmit an RF signal. The signal path on the probe card is minimized, and an impedance matching circuit is provided between the probe and the coaxial cable as necessary. Below are some examples of prior art related to this.

  The “method for inspecting a high-frequency / high-speed device” disclosed in Patent Document 1 solves the problem of discontinuity in the connection portion between the packaged device to be inspected and the inspection apparatus, and is caused only by the design matters of the device to be inspected. It is a method that can obtain the data to be. As shown in FIG. 6 (a), on one side of the metal block, RF signal probes (input probes and output probes), power supply probes, and portions corresponding to the electrode terminals of the device to be inspected, The grounding probe is provided so that the tip of the movable pin protrudes. An impedance matching device is connected to the end of the RF signal probe opposite to the connection with the device under test via a coaxial cable. Inspection is performed after the connection between the device under test and the RF signal probe is matched.

  The “development test probe card” disclosed in Patent Document 2 enables an analog IC to be measured by a tester for a digital IC. As shown in FIG. 6B, an analog signal generator generates an input analog signal for input. Impedance matching means suppresses the attenuation of the input analog signal. Input analog signals are input to the object to be measured by analog signal input means arranged on the surface to be measured. The analog signal acquisition means arranged on the surface to be measured opposes the output analog signal output by the device to be measured. The analog-to-digital conversion means converts the output analog signal into a digital signal that can be handled by the digital tester. The digital signal converted and generated by the analog / digital converting means is transmitted to the digital tester by the digital signal transmitting means.

  The “semiconductor integrated circuit device test system” disclosed in Patent Document 3 enables high-precision measurement using a general semiconductor integrated circuit device inspection device (tester). As shown in FIG. 6C, an input signal conversion circuit is provided before the analog-digital conversion circuit on the probe card. Examples of the input signal conversion circuit include a voltage level conversion circuit, an impedance matching circuit, an integration circuit, and a circuit in which these circuits are connected in series. As a result, highly accurate measurement that matches the measurement purpose can be performed.

The “probe card assembly of a high-band passive integrated circuit tester” disclosed in US Pat. No. 6,057,096 is substantially less than level by greatly improving the frequency response of the signal path and minimizing the length and impedance of the signal path. This is a method that reduces the distortion and attenuation of the signal. As shown in FIG. 6D, the probe card assembly is a signal path for transmitting a high frequency signal between a bonding pad of an integrated circuit (IC) and an IC tester. The frequency response of the probe card assembly is optimized, such as by impedance matching of the signal path, so that the signal path is a properly tuned Butterworth filter or Chebyshev filter.
Japanese Patent Laid-Open No. 2003-232834 JP 2006-084296 A JP 2006-138787 A JP 2007-178440 JP

  However, the conventional method has the following problems. In the high-frequency device measurement method for package IC, a coaxial probe is used and impedance is matched by an impedance matching circuit. In the coaxial probe type probe card, the impedance of the coaxial probe and the impedance of the coaxial cable are substantially the same, and the deviation of the impedance is small. Therefore, even if a fixed impedance matching device is used, impedance matching can be substantially achieved. If a variable impedance matching device is used, impedance matching can be made more precisely. However, using a coaxial probe is expensive.

  In a low-cost cantilever type probe card, since the impedance deviation of the cantilever is large, the impedance of each cantilever and the impedance of the coaxial cable cannot be finely matched by using a fixed impedance matching device. Even if a variable impedance matching unit for a coaxial probe is simply applied to a high frequency cantilever type probe card for inspection at the wafer level, the size and cost are increased. Since there is no small and low-cost variable impedance matching unit capable of matching the impedance between the cantilever and the coaxial cable, there is no suitable method for absorbing the impedance deviation in the manufacturing stage of the high-frequency probe card for inspection at the wafer level.

  The object of the present invention is to solve the above-mentioned conventional problems, to easily and appropriately match the impedance of the cantilever and the coaxial cable, and to easily absorb the impedance deviation of the cantilever. This is to realize a high-frequency probe card at a low cost.

  In order to solve the above-described problems, in the present invention, a high-frequency probe card is composed of a cantilever that makes contact with a test pad of an integrated circuit to be inspected, two trimmer capacitors connected to the cantilever, and one multilayer inductor. A variable impedance matching circuit of a type matching circuit and a connector for connecting a coaxial cable connected to the measuring instrument and connected to the variable impedance matching circuit are provided.

  With the above configuration, the impedance deviation in the manufacturing stage of the high-frequency cantilever type probe card for inspection at the wafer level can be absorbed by individual adjustment, and the low-cost cantilever type probe card can be used even at high frequency. .

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to FIGS.

  In the embodiment of the present invention, a variable impedance matching circuit of a π-type matching circuit composed of two trimmer capacitors and one multilayer inductor is connected to a cantilever to match impedance, and is connected to the variable impedance matching circuit. A probe card is a probe card in which a coaxial cable is connected to a connector and connected to a measuring instrument, and a cantilever is brought into contact with a test pad of an integrated circuit to be tested.

  FIG. 1 is a conceptual diagram showing how a probe card and a tester are connected in an embodiment of the present invention. FIG. 2 is a conceptual diagram showing the configuration of the probe card. FIG. 3 is a circuit diagram of a variable impedance matching circuit provided in the probe card. FIG. 4 is a conceptual diagram of the connector connecting portion of the probe card. FIG. 5 is a cross-sectional view of the microstrip line of the probe card.

  1 to 5, a probe card 1 is an input / output unit for a test signal between a device under test and a tester. This is a four-layer printed board with an insulating substrate thickness of 2 mm. The insulating substrate may be a double-sided substrate. The variable impedance matching circuit 2 is a circuit that matches the impedance of the cantilever and the coaxial cable. The cantilever 3 is a probe that is connected to an inspection electrode of a device to be inspected. The tester 4 is a measuring instrument that inspects the characteristics of the device under test. Use one that has the ability to measure signals above 3 GHz. The coaxial cable 5 is a signal cable that connects the probe card and the tester. The characteristic impedance is 50Ω. The coaxial connector 6 is a connector for connecting a coaxial cable to the probe card. The device under test 7 is a device to be inspected. The trimmer capacitor 8 is a small variable capacitor whose capacity can be adjusted manually. The thickness is about 2 mm, the diameter is about 3 mm, and the maximum capacitance is 10-1 pF. The through hole 9 is a hole for accommodating the trimmer capacitor. The multilayer inductor 10 is a planar coil having an inductance of 0.1 to 10 nH. For these capacitances and inductances, appropriate values are selected according to the device to be inspected.

  The function and operation of the probe card in the embodiment of the present invention configured as described above will be described. First, the outline of the function of the probe card will be described with reference to FIG. A variable impedance matching circuit 2 of a π-type matching circuit composed of two trimmer capacitors 8 and a laminated inductor 10 is connected to the cantilever 3. A coaxial connector 6 for coupling a coaxial cable 5 connected to the tester 4 is connected to the variable impedance matching circuit 2. The cantilever 3 is brought into contact with the inspection pad of the device under test 7 and the variable impedance matching circuit 2 is individually adjusted to absorb the impedance deviation in the manufacturing stage of the cantilever type probe card 1. A test signal is generated by the tester 4, the test signal is applied to the device under test 7 via the coaxial cable 5, the variable impedance matching circuit 2, and the cantilever 3, and the response signal from the device under test 7 is tested through the reverse path. 4 to measure the characteristics of the device under test 7.

  Next, the configuration of the probe card will be described with reference to FIG. A cantilever 3 as a probe is provided below the insulating substrate of the probe card 1. This is the same as the cantilever of a conventional cantilever type probe card. A conductor pattern for a coaxial connector is formed on both ends of the insulating substrate of the probe card 1 and the coaxial connector 6 is attached. A laminated inductor is provided between the cantilever 3 and the coaxial connector 6. Two trimmer capacitors 8 are provided between both ends of the multilayer inductor 10 and the ground. The trimmer capacitor 8 is accommodated in the through hole 9 of the insulating substrate so that it can be adjusted from the front side.

  Next, the variable impedance matching circuit will be described with reference to FIG. The variable impedance matching circuit 2 is a π-type matching circuit including two trimmer capacitors 8 and a multilayer inductor 10. By adjusting the trimmer capacitor 8 on the cantilever 3 side and the trimmer capacitor 8 on the coaxial connector 6 side, the difference in impedance between the cantilever 3 and the coaxial cable 5 can be absorbed. Since the cantilever 3 has a structure in which one conductor is exposed, the grounding capacitance easily changes, and the characteristic impedance cannot be made constant. In addition, deviations in the manufacturing process are unavoidable, for example, soldering cannot be made uniform at all. Therefore, the characteristic impedance of the cantilever 3 cannot be matched with the input / output impedance of the device under test and the characteristic impedance of the coaxial cable. Therefore, the trimmer capacitor 8 of the π-type matching circuit connected to the cantilever 3 is individually adjusted to match the impedance. By doing so, the impedance of all the cantilevers 3 can be matched with the coaxial cable 5 and the device under test.

  Next, the conductor pattern of the connector connecting portion will be described with reference to FIG. In order to attach the coaxial connector 6 to the insulating substrate of the probe card 1, a conductor pattern is formed on the insulating substrate. At this time, the conductor pattern is formed so that the impedance of the transmission line matches the impedance of the coaxial cable 5 so that impedance mismatch does not occur.

  Next, the microstrip line will be described with reference to FIG. The transmission line connecting the cantilever 3 and the multilayer inductor 10 and the transmission line connecting the multilayer inductor 10 and the coaxial connector 6 are configured by microstrip lines. The microstrip line is formed by providing a conductor pattern on the insulating substrate of the probe card 1. The width of the conductor pattern having a thickness of 18 μm is 0.7 mm, and the thickness of the insulating substrate having a dielectric constant of 4.5 to the ground layer is 0.4 mm. The transmission impedance of the microstrip line on the coaxial connector 6 side is set to 50 Ω which is the same as that of the coaxial cable 5. The transmission impedance of the microstrip line on the cantilever 3 side is set to be substantially the same as that of the cantilever 3. A coplanar line may be used instead of the microstrip line.

  As described above, in the embodiment of the present invention, the probe card is matched to the impedance by connecting the variable impedance matching circuit of the π-type matching circuit composed of two trimmer capacitors and one multilayer inductor to the cantilever, A coaxial cable is connected to a connector connected to a variable impedance matching circuit, connected to a measuring instrument, and the cantilever is in contact with the test pad of the integrated circuit to be inspected. The impedance deviation in can be absorbed by individual adjustment.

  The high-frequency probe card of the present invention is most suitable as a probe card for measuring an integrated circuit of a semiconductor wafer at a high frequency.

It is a conceptual diagram which shows a mode that the probe card and tester in the Example of this invention are connected. It is a conceptual diagram which shows the structure of the probe card in the Example of this invention. It is a circuit diagram of the variable impedance matching circuit provided in the probe card in the Example of this invention. It is a conceptual diagram of the connector connection part of the probe card in the Example of this invention. It is sectional drawing of the microstrip line | wire of the probe card in the Example of this invention. It is a conceptual diagram of the conventional probe card.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Probe card 2 Variable impedance matching circuit 3 Cantilever 4 Tester 5 Coaxial cable 6 Coaxial connector 7 Device under test 8 Trimmer capacitor 9 Through hole
10 multilayer inductors

Claims (1)

A cantilever that is brought into contact with a test pad of an integrated circuit to be inspected; a variable impedance matching circuit of a π-type matching circuit that is connected to the cantilever and includes two trimmer capacitors and one laminated inductor; and the variable impedance matching circuit And a connector for coupling a coaxial cable connected to the measuring instrument.

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