JP2009156580A - Input capacitance measuring circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an input capacitance measuring circuit which is capable of measuring at a high speed an input capacitance to a pin electronics part from a probe card of a semiconductor testing device. <P>SOLUTION: The input capacitance measuring circuit measures the input capacitance to the pin electronics part 201 from a device interface part to which DUT is connected directly. The circuit has a waveform generating part 110 which is provided in the device interface part and outputs a square wave signal through the medium of a known output resistance 8, and a capacitance measuring part 12 which is provided in the pin electronics part 201 and measures the input capacitance, based on an input signal waveform of the pin electronics part 201 on which an output signal of the waveform generating part 110 is impressed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an input capacitance measurement circuit that measures the input capacitance of a pin electronics unit connected to a probe card, a performance board, or the like in a semiconductor test apparatus such as an LSI tester.

  In general, a semiconductor test apparatus gives a test signal to an IC, LSI, or the like, which is an object to be tested (hereinafter referred to as “DUT”), measures the output of the DUT, and determines whether the DUT is good or bad. Such a semiconductor test apparatus generally includes a test head and a performance board, and the DUT and the semiconductor test apparatus are electrically connected from the test head via the performance board.

That is, when testing a packaged DUT, an IC socket is prepared on the performance board, the DUT is mounted on the IC socket, the DUT is connected to a semiconductor test apparatus, and the test is performed.
On the other hand, in the case of a semiconductor test apparatus that performs tests at the wafer stage in the manufacturing process, a connection tool called a contact ring is mounted on the performance board, and connected to the probe card via this connection tool. And electrically connected.

The probe card is a card on which a needle connected to a DUT (wafer) is mounted. It is necessary to measure the input capacity from this probe card to the pin electronics unit in order to confirm how much capacity is loaded on the DUT in the standard specifications and optional specifications and the actual test is performed.

FIG. 4 is a block diagram showing a conventional input capacitance measuring circuit for measuring the input capacitance from the probe card of the LSI tester to the pin electronics section.

The probe card 100 is connected to a DUT (wafer) (not shown) via a needle. In the pin electronics unit 200 in the test head 400, the output terminal of the probe card 100 is connected to the input unit via a connector. The input capacitance measuring circuit 300 includes an LCR meter, an impedance analyzer, etc., and measures the input capacitance of the pin electronics unit 200.

The operation of the circuit of FIG. 4 will be described below. In the DUT test mode, a signal output from the DUT is transmitted to the pin electronics unit 200 via the probe card 100, and the DUT is evaluated and determined in the pin electronics unit 200.

When measuring the input capacitance of the pin electronics unit 200, the input terminal of the pin electronics unit 200 is connected to the output terminal of the input capacitance measurement circuit 300.
A sine wave signal is applied from the input capacitance measurement circuit 300 to the pin electronics unit 200, and the input capacitance of the pin electronics unit 200 is measured based on the phase shift of the input waveform.

  Prior art documents related to the input capacitance measuring circuit include the following.

Japanese Patent Laid-Open No. 07-146335

  However, in the conventional method, since measurement is performed manually for each pin using an LCR meter or an impedance analyzer, it takes a long time to measure the capacity of an LSI tester having a large number of pins. In addition, when the configuration of the pin electronics section is changed due to the enhancement of the function of the LSI tester, data must be acquired again for all pins.

  The present invention is intended to solve such a problem, and provides an input capacitance measuring circuit that can measure the input capacitance from the device interface unit to the pin electronics unit at high speed, which includes a probe card of a semiconductor test apparatus or the like. The purpose is to do.

In order to achieve such a problem, the invention according to claim 1 of the present invention is:
In an input capacitance measuring circuit for measuring an input capacitance from a device interface unit to which a DUT is directly connected to a pin electronics unit,
A waveform generating unit provided in the device interface unit for outputting a square wave signal via a known output resistor;
A capacitance measuring unit that is provided in the pin electronics unit and measures the input capacitance based on an input signal waveform of the pin electronics unit generated when an output signal of the waveform generation unit is applied. .

The invention according to claim 2
The input capacitance measuring circuit according to claim 1,
The capacitance measuring unit calculates the input capacitance based on an output from an AD converter corresponding to the input signal waveform and a value of the output resistance.

The invention described in claim 3
The input capacitance measuring circuit according to claim 1,
The capacitance measuring unit calculates the input capacitance based on an output from a comparator corresponding to the input signal waveform and a value of the output resistance.

The invention according to claim 4
In the input capacitance measuring circuit according to any one of claims 1 to 3,
The waveform generator is provided with a change-over switch that outputs a square wave signal to the plurality of pin electronics units via the output resistor.

The invention according to claim 5
The input capacitance measuring circuit according to any one of claims 1 to 4,
The device interface unit includes a probe card.

The invention described in claim 6
The input capacitance measuring circuit according to any one of claims 1 to 4,
The device interface unit includes a performance board.

  As is apparent from the above description, according to the present invention, in the input capacitance measuring circuit for measuring the input capacitance from the device interface unit to which the DUT is directly connected to the pin electronics unit, the device interface unit is provided. A waveform generator that outputs a square wave signal via a known output resistor, and a pin electronics unit provided on the basis of the input signal waveform of the pin electronics unit that is generated when the output signal of the waveform generator is applied By providing the capacitance measuring unit that measures the input capacitance, it is possible to provide an input capacitance measuring circuit that measures the input capacitance from the probe card of the semiconductor test apparatus to the pin electronics unit at high speed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an example of an input capacitance measuring circuit for measuring input capacitance from a device interface unit to a pin electronics unit of a semiconductor test apparatus according to an embodiment of the present invention, and a case where a probe card is used as a device interface unit. FIG. The same parts as those in FIG. 4 are denoted by the same symbols, and redundant description is omitted.

Here, an LSI tester similar to that shown in FIG. 4 is used as the semiconductor test apparatus. The waveform generator 110 is provided on the probe card 100 and outputs a square wave signal via the known output resistor 7. The pin electronics unit 201 is provided in the test head 400 and measures the input capacitance based on the input waveform of the signal input from the waveform generation unit 110.

In the waveform generator 110, the selector switch 5 has one input connected to the voltage V1 of the first reference voltage 1 via the voltage buffer amplifier 3, and the other input to which the voltage V2 of the second reference voltage 2 is a voltage. Connection is made via a buffer amplifier 4. The pulse generator 6 uses the LSI tester originally provided, and drives the changeover switch 5 to alternately switch the two inputs. The voltage buffer amplifier 7 performs impedance conversion on the output of the changeover switch circuit 5. One end of the output resistor 8 is connected to the output terminal of the voltage buffer amplifier 7, and the other end is connected to the input unit of the pin electronics unit 201 via a connector.

In the pin electronics unit 201, the relay 9 opens and closes the connection between the other end of the output resistor 8 of the waveform generation unit 110 and the input amplifier 10. The input amplifier 10 amplifies a waveform generated at the input of the input amplifier 10 by a rectangular wave signal applied via the output resistor 8 and the relay 9. The AD converter 11 converts the output of the input amplifier 10 into a digital signal. The capacitance measuring unit 12 measures the input capacitance of the pin electronics unit 201 based on the output of the AD converter 11.

In the above description, the capacitance measuring unit 12 is provided in addition to the normal pin electronics unit, but the relay 9, the input amplifier 10 and the AD converter 11 which are other components are originally provided in the pin electronics unit. Use functions.

Further, in the above, the probe card 100 constitutes a device interface unit to which the DUT is directly connected, and is connected to the pin electronics unit.

The operation of the circuit of FIG. 1 will now be described. When the reference voltages V1 and V2 of the reference voltage sources 1 and 2 are set, a voltage having the same potential as the reference voltages V1 and V2 is applied to the input portion of the changeover switch 5 via the voltage buffer amplifiers 3 and 4. When the pulse generator 6 is operated, a square wave signal in which V1 and V2 are alternately repeated is output to the output side of the changeover switch 5 and sent to the pin electronics unit 201 via the voltage buffer amplifier 7 and the output resistor 8. . A signal input to the pin electronics unit 201 is amplified by the input amplifier 10 via the relay 9 in the closed state, and converted into digital data by the AD converter 11. This digital data is input to the capacitance measuring unit, and the input capacitance at the input of the input amplifier 10 is measured as follows.

The signal waveform output from the waveform generation unit 110 is a square wave (voltage) at the output terminal of the voltage buffer amplifier 7, but the input waveform of the pin electronics unit 201 is 1 due to the action of the input capacitance and the output resistance 8. The voltage changes in the next response waveform.

FIG. 2 is a time chart showing the waveform of the input signal (voltage) Vin generated at the input section of the input amplifier 10 of the pin electronics section 201. This primary response waveform is converted into digital data by the AD converter 11 via the input amplifier 10, and based on the output data, the time constant τ (the time required until about 63% change point) is converted by the capacitance measuring unit 12. Since the measured resistance value R of the output resistor 8 is accurately known, the input capacitance C of the pin electronics unit 201 can be easily calculated from C = τ / R.

According to the input capacitance measuring circuit configured as described above, an input capacitance measuring circuit capable of measuring the input capacitance from the probe card of the semiconductor test apparatus to the pin electronics section at high speed can be realized. Therefore, by mounting this function on an LSI tester, the input capacitance can be easily measured in the case of standard specifications or when an optional circuit is added to the pin electronics section. That is, the user can easily grasp how much capacity is loaded on the device and the actual test is performed.

In addition, since a special measuring instrument such as an LCR meter or an impedance analyzer is not required, the cost can be reduced.

In the above embodiment, the AD converter originally provided in the pin electronics section is used. However, since the pin electronics section is often provided with a comparator, this is used as in the following embodiment. It may be used.

FIG. 3 is a configuration block diagram showing a second example of the input capacitance measuring circuit according to the embodiment of the present invention, in which a comparator provided in the pin electronics unit 202 is used instead of the AD converter. The same parts as those in FIG. 1 are denoted by the same symbols, and redundant description is omitted.

In the waveform generator 111, the changeover switch 13 switches the square wave signal output from the voltage buffer 7 via the output resistor 8 to the plurality of pin electronics units 202 and outputs it.

In the pin electronics unit 202, the comparator 14 inputs the output signal of the input amplifier 10 and compares it with the threshold voltage Vth set by the DA converter 15. Here, the threshold voltage Vth is set to a value of about 63% change point (FIG. 2) corresponding to the time constant τ. The capacitance measuring unit 12a calculates the input capacitance based on the output signal of the comparator 14 and the value of the output resistance 8 of the waveform generating unit 111.

As described above, the comparator 14 and the DA converter 15 can utilize the functions originally provided in the pin electronics unit.

The operation of the circuit of FIG. 3 will now be described. A signal output from the voltage buffer amplifier 7 of the waveform generator 111 is input to the pin electronics unit 202 selected by the changeover switch 13 via the output resistor 8. A signal waveform similar to that shown in FIG. 2 is generated at the input section of the selected pin electronics section 202 and is compared with the threshold voltage Vth by the comparator 14 via the input amplifier 10, and the time constant with respect to the inversion timing of the pulse generation section 6. Inversion occurs with a delay corresponding to τ. This delay time τ is measured in the capacitance measuring unit 12a using a known means such as a clock counter, and thereafter, the input capacitance C of the pin electronics unit 202 can be easily obtained in the same manner as in the circuit of FIG.

According to the input capacitance measuring circuit configured as described above, since the comparator is used to measure the time constant τ, the capacitance can be measured at a higher speed than when the AD converter of FIG. 1 is used. Therefore, when the pin electronics part of an LSI tester has not only an AD converter but also a comparator (that is, each pin has a digitizer (AD converter) and a comparator), it is better to realize this function with a comparator. The effect increases as the number of pins increases. In the case of the above-mentioned embodiment, one LSI tester is provided with a pin electronics section of 1000 to 3000 pins.

In the above embodiment, the waveform generation unit 111 may be realized in a diagnostic probe card of an LSI tester, for example. In this case, one waveform generator 111 is provided in the diagnostic probe card, and the output signal is distributed to each pin electronics unit 202 by the changeover switch 13.

When the number of pins is large, the number of relays can be reduced by configuring the changeover switch 13 with a tournament relay or the like.

Similarly, in the input capacitance measuring circuit of FIG. 1, the output signal of the waveform generation unit can be distributed to a plurality of pin electronics units using the changeover switch 13.

In addition, the waveform generators 110 and 111 are not limited to the above method, and any rectangular wave generation method in which the waveform values (V1, V2) are accurately known can be used.

Further, the present invention can be applied not only to the probe card but also to any device interface unit to which the DUT is directly connected. For example, when the DUT is a single device, it is possible to measure the input capacity from the performance board to the pin electronics unit in the same way by using a performance board as the device interface unit and providing a waveform generation unit on the diagnostic performance board. it can.

It is a block diagram showing a configuration of an example of an input capacitance measuring circuit according to an embodiment of the present invention. 6 is a time chart showing a waveform of an input unit of the pin electronics unit 201. It is a block diagram showing a second example of the input capacitance measuring circuit according to the embodiment of the present invention. It is a block diagram which shows the conventional input capacitance measuring circuit which measures the input capacitance from the probe card of a LSI tester to a pin electronics part.

Explanation of symbols

8: Output resistor 11: AD converter 12, 12a: Capacitance measuring unit 13: Changeover switch 14: Comparator 110, 111: Waveform generating unit 201, 202: Pin electronics unit

Claims (6)

In an input capacitance measuring circuit for measuring an input capacitance from a device interface unit to which a DUT is directly connected to a pin electronics unit,
A waveform generating unit provided in the device interface unit for outputting a square wave signal via a known output resistor;
A capacitance measuring unit that is provided in the pin electronics unit and measures the input capacitance based on an input signal waveform of the pin electronics unit generated when an output signal of the waveform generation unit is applied. Input capacitance measurement circuit. The input capacitance measuring circuit according to claim 1, wherein the capacitance measuring unit calculates the input capacitance based on an output from an AD converter corresponding to the input signal waveform and a value of the output resistance. The input capacitance measuring circuit according to claim 1, wherein the capacitance measuring unit calculates the input capacitance based on an output from a comparator corresponding to the input signal waveform and a value of the output resistance. 4. The input capacitor according to claim 1, wherein the waveform generation unit includes a changeover switch that switches a square wave signal to the plurality of pin electronics units via the output resistor and outputs the square wave signal. 5. Measuring circuit.   The input capacitance measuring circuit according to claim 1, wherein the device interface unit includes a probe card.   5. The input capacitance measuring circuit according to claim 1, wherein the device interface unit is configured by a performance board.

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