JP2006128351A - System and method for measuring capacity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide capacity measuring system/method with which capacity can highly precisely be measured where a rear face of a wafer is set to be one electrode. <P>SOLUTION: The capacity measuring system is provided with a stage 10 where the wafer 1 is placed and fixed and with a tester 20. The system measures capacity 3 where the rear face of the wafer is formed as one electrode. The stage is provided with a conductive chuck 11, an electric shielding member 14 which is disposed below the chuck and is insulated from a periphery, and a back plate 13 supporting the conductive chuck 11 and the electric shielding member 14. The tester is provided with a first measurement terminal to which a probe is connected, a base measurement terminal 24 connected to the conductive chuck and a measurement ground terminal 27 connecting the electric shielding member to measurement ground. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a capacity measuring system and a capacity measuring method for measuring a capacity formed on a wafer, and more particularly to a capacity measuring system and a capacity measuring method for measuring a capacity using the back surface of a wafer as one electrode.

  In the manufacturing process of an electronic element such as a semiconductor element, a large number of elements are formed on a thin plate-like wafer such as a semiconductor wafer. The elements formed on the wafer are separated and assembled into electronic components, but before the separation, a probe test is performed to test whether each element formed on the wafer operates normally.

  In the probe test, a wafer is placed on a prober stage and fixed, and the probe is brought into contact with an electrode on the wafer. After that, a signal is supplied from the tester to the probe, and the signal output to the probe is detected by the tester to check whether it operates normally. For example, various electronic elements such as a semiconductor integrated circuit, a resistor, and a capacitor are formed on the wafer. In the case of a semiconductor integrated circuit, a large number of transistors, resistors, capacitors, wirings connecting them, and the like are formed. In order to test them, it is necessary to contact a large number of probes. Further, when measuring resistance or capacitance, measurement is performed by contacting a probe to electrodes at both ends of the resistance and capacitance. Probers and testers are dedicated to testing and measuring various electronic devices such as semiconductor integrated circuits, resistors, and capacitors, and dedicated to testing and measuring specific electronic devices. There may be. Since the present invention relates to the measurement of capacitance, the prober and tester for measuring capacitance will be described as an example. However, the present invention can also be applied to a general-purpose prober and tester for testing and measuring other electronic devices.

  FIG. 1 is a diagram showing a schematic configuration of a conventional probe measurement system. As shown in FIG. 1, the wafer 1 is fixed to a prober stage 10 by vacuum suction or the like. The stage 10 includes a conductive chuck 11 on which the wafer 1 is placed so that the back surface is in contact, a back plate 13 that supports the conductive chuck 11, and an electrical shield member (plate that is provided inside the back plate 13. ) 14 and a heater 15 provided on the lower side of the electrical shield member 14. The heater 15 is formed by covering the heating element 16 with a high insulator such as silicone, mica, polyimide, etc., and generates heat when a current is supplied from the heating circuit 17 to the heating element 16.

  The probe measurement may be performed at a high temperature or a low temperature depending on the specifications of the usage environment of the electronic element. Such a measurement is performed by setting the stage on which the wafer is placed to a predetermined temperature and placing the wafer on the placed wafer. Is performed at a predetermined temperature. The heater 15 is used to bring the stage 10 to a high temperature state. The stage is cooled by flowing the coolant or air through the coolant or air conduit provided inside or below the conductive chuck 11, but the description is omitted because it is not directly related to the present invention. . In the example of FIG. 1, the example in which the heater 15 is provided has been described, but the heater 15 may not be provided if the measurement does not require temperature adjustment.

  In the conventional example of FIG. 1, the back plate 13 is made of an insulating material. The conductive chuck 11 has a terminal 18, and the conductive chuck 11 is set to a predetermined potential by supplying a predetermined potential to the terminal 18.

  In general, the probes 41 and 42 that contact the electrodes on the wafer are provided between the prober and the tester, and the terminals of the tester are connected to the probes 41 and 42.

  The tester 20 generates a test signal and detects an electric signal output from the electronic element to be inspected, terminals 22 and 23 connected to the probes 41 and 42, and terminals of the conductive chuck 11 18, a switch 25 that switches connection of the terminal 23 to the signal processing unit 21, and a switch 26 that switches connection of the terminal 24 to the signal processing unit 21 are provided. The signal processing unit 21 includes, for example, a DC measurement unit and an LCR measurement unit.

  When measuring the capacitance 2 formed on the wafer 1 and the electrodes at both ends of the wafer 1 formed on the surface of the wafer 1, as shown by broken lines in FIG. The measurement is performed in contact with the electrode. At this time, the switch 25 is connected to the LCR measurement unit side, and the probes 41 and 42, that is, the terminals at both ends of the capacitor 2 are connected to the LCR measurement unit of the signal processing unit 21. Further, the terminal 18 of the conductive chuck 11 is connected to the terminal 24 of the tester 20, the switch 26 is connected to the DC measurement unit, and 0 V is applied to the conductive chuck 11, thereby causing noise from the lower heater 15. Is cut off, and high-precision measurement can be performed stably.

  Here, the terminal of the signal processing unit 21 connected to the terminal 22 is referred to as a first measurement terminal, and the terminal of the signal processing unit 21 connected to the terminal 23 is referred to as a second measurement terminal. The terminal 24 of the tester 20 to be connected is referred to as a base measurement terminal. Accordingly, the base measurement terminal 24 can be connected to either the second measurement terminal or the noise shield.

  On the other hand, when a capacitor is formed on a wafer, one electrode of the capacitor may be provided on the upper surface of the wafer and the other electrode may be provided on the back surface of the wafer. The prober and tester 20 shown in FIG. 1 is also used when measuring such a capacity. Such a measurement of the capacitance 3 is performed under the connection shown by a solid line in FIG. The difference from the case of measuring the capacitance 2 is that the probe 42 is not used and the switch 26 is connected to the second measurement terminal side. One electrode of the capacitor 3 is connected to the first measurement terminal of the signal processing unit 21 via the probe 41 and the terminal 22, and the other electrode of the capacitor 3 is the conductive chuck 11, the terminals 18, 24, and the switch 26. To the second measurement terminal of the signal processing unit 21.

JP 2004-63486 A JP-A-11-1111789 Japanese Patent Laid-Open No. 2003-1000082

  In the configuration shown in FIG. 1, when measuring the capacitance 3 having electrodes on the upper and lower surfaces of the wafer, the electrical shield member 14 provided under the conductive chuck 11 acting as the measurement electrode is connected to the frame ground of the prober. It is connected, and the influence of the noise of the heater on the conductive chuck 11 is reduced. However, in recent years, there has been a demand for higher accuracy in capacity measurement, and it has been found that the configuration shown in FIG. 1 cannot sufficiently satisfy this requirement.

  An object of the present invention is to realize a capacitance measuring system and a capacitance measuring method capable of measuring capacitance with the back surface of a wafer as one electrode with higher accuracy.

  In order to achieve the above object, according to the capacity measuring system and the capacity measuring method of the present invention, an electrical shield member provided under a conductive chuck acting as a measuring electrode is connected to a measurement ground of a tester. Specifically, the electrical shield member is electrically insulated from the surroundings, a measurement ground terminal connected to the measurement ground of the tester is provided, and the electrical shield member is connected to the measurement ground terminal of the tester.

  That is, the capacity measurement system of the present invention is a capacity measurement system that includes a stage on which a wafer is placed and fixed, and a tester, and the capacity formed by using the back surface of the wafer as one electrode is measured by the tester. The stage includes a conductive chuck on which the back surface of the wafer is placed, an electrical shield member provided below the conductive chuck and insulated from the surroundings, the conductive chuck, and the electrical chuck A back plate for supporting a static shield member, wherein the tester includes a first measurement terminal to which a probe that contacts an electrode is connected to the surface of the wafer, and a base measurement terminal connected to the conductive chuck. A measurement ground terminal for connecting the electrical shield member to the measurement ground, and in a state where the electrical shield member is connected to the measurement ground. And measuring the capacitance.

Further, the capacity measuring method of the present invention is a capacity measuring method for measuring a capacity formed by using the back surface of the wafer as one electrode, on the conductive chuck electrically insulated from the other part. The tester probe is brought into contact with the electrode on the surface of the wafer,
The conductive chuck is connected to a base measurement terminal of the tester, an electrical shield member provided on the lower side of the conductive chuck is connected to a measurement ground of the tester, and the capacitance is measured. To do.

  According to the invention, the electrical shield member under the conductive chuck acting as a measurement electrode is connected to the measurement ground of the tester. As a result, it was experimentally confirmed that the measurement accuracy was improved as compared with the conventional case.

  According to the present invention, the accuracy of capacitance measurement is improved.

  FIG. 2 is a diagram showing the configuration of the capacity measurement system according to the first embodiment of the present invention. The prober stage 10 has a configuration similar to that of the stage shown in FIG. 1 except that a terminal 19 connected to the electrical shield member 14 is provided. The tester 20 also has a similar configuration to the tester shown in FIG. 1 except that a measurement ground terminal 27 connected to the measurement ground GND of the tester 20 is provided.

  As shown in FIG. 2, with the switch 25 connected to the LCR measurement unit and the switch 26 connected to the second measurement terminal (LCR measurement unit), the probe 41 connected to the terminal 22 is connected to the wafer of capacity 3. 1, the terminal 18 of the conductive chuck 11 is connected to the terminal 24, and the terminal 19 is connected to the terminal 27. As a result, the probe 41 is connected to the first measurement terminal, the conductive chuck 11 is connected to the second measurement terminal, and the electrical shield member 14 is connected to the measurement ground GND of the tester, so that measurement can be performed with high accuracy. The

  It is also possible to measure the capacitance 2 in which the electrodes on both sides as shown in FIG. 1 are provided on the surface of the wafer 1 with the configuration of the first embodiment of FIG. In this case, as in FIG. 1, the switch 25 is connected to the LCR measurement unit, the probe 41 is connected to one electrode on the surface of the wafer 1, and the prober 42 connected to the terminal 23 is connected to the surface of the wafer 1. Connected to the other electrode on the top, the switch 26 is connected to the LCR measurement unit in the same manner.

  FIG. 3 is a diagram showing the configuration of the capacity measurement system according to the second embodiment of the present invention. The system of the second embodiment is different from the first embodiment in that the back plate 13 is made of a conductive material and the insulating member 12 is provided between the conductive chuck 11 and the back plate 13. With this configuration, the capacitance between the conductive chuck 11 and the electrical shield member 14 can be reduced, and the measurement accuracy can be further improved.

  As shown in FIG. 2, in the first embodiment, a configuration similar to the conventional configuration in which a plate-shaped electrical shield member 14 is disposed on the heater 15 is used. It is also possible to use a heater 30 having an electrical shield member as shown in FIG. In this case, the electrical shield member 14 can be removed.

As shown in FIG. 4, the heater 30 has a planar heating element 16 in the center, covers the front and back of the planar heating element 16 with an insulating material 31 having a high heat resistance temperature such as mica and polyimide, and an electrical shielding material 32. Are provided on the front and back sides and further covered with an insulating material 33. As the insulating material 33, the same material as the insulating material 31 is generally used, but a high insulating material having excellent thermal conductivity is selected. A conductive wire 34 is connected to the planar heating element 16, and a conductive wire 35 is connected to the electrical shield material 32. The conducting wire 34 is connected to the heating device 17 in FIG. 2, and the conducting wire 35 is connected to the terminal 27 in FIG.
It is also possible to use the heater 30 of FIG. 4 in the second embodiment of FIG.

  4, when silicone rubber is used as the insulating materials 31 and 33, the heat-resistant temperature of the heater 30 is about 200 ° C. If mica (mica) is used as the insulating materials 31 and 33, The heat-resistant temperature is improved to about 300 ° C., and measurement under higher temperature conditions becomes possible.

  FIG. 5 shows the difference in measurement accuracy between the conventional example of FIG. 1, the first example of FIG. 2, and the second example of FIG. 3 when measuring the capacitance 3 formed with the back surface of the wafer as one electrode. It is the experimental data shown. This is measurement data when the capacitance formed on the wafer 11 is measured by changing the frequency of the measurement signal to be applied, and is a standard deviation of the measurement value of 100 times measurement. Show. The broken line graph is the measurement data in the configuration of FIG. 1, and is the data when the electrical shield member 14 is connected to the frame ground FG of the prober. The one-dot chain line graph is measurement data in the configuration of the first embodiment of FIG. 2, and is data in a state where the electrical shield member 14 is connected to the measurement ground GND of the tester 20. Also, the solid line graph is the measurement data in the configuration of the second embodiment of FIG. 3, and is the data when the insulating member 12 is mounted between the conductive chuck 11 and the electrical shield member 14 to achieve high insulation. is there.

  In a state where the conventional electrical shield member 14 is not connected to the measurement ground GND of the tester 20, the standard deviation of the measurement value in a high frequency region of 10 KHz or more is large, and noise (noise) current is in that region. You can see it grows. This is presumably because the measurement signal is susceptible to noise on the tester side and is also susceptible to induction noise of the prober itself.

  In contrast, when the electrical shield member 14 of FIG. 2 is connected to the measurement ground, the standard deviation of the measurement value in the high frequency region of 10 KHz or more remains low compared to the conventional example. However, the standard deviation gradually increases in a high frequency region of 150 KHz or higher.

  Furthermore, when the insulating member 12 of FIG. 3 is mounted between the conductive chuck 11 and the electrical shield member to achieve high insulation, the standard deviation hardly increases even in a high frequency region of 150 KHz or higher.

  As described above, by applying the present invention, the measurement accuracy of the capacitance at a high frequency is improved.

  As described above, according to the present invention, the measurement accuracy of the capacitance particularly in the high frequency region is improved, and the capacitance used for the circuit operating at a high frequency can be selected more accurately.

It is a figure which shows the structure of the conventional capacity | capacitance measurement system. It is a figure which shows the structure of the capacity | capacitance measuring system of 1st Example of this invention. It is a figure which shows the structure of the capacity | capacitance measuring system of 2nd Example of this invention. It is a figure which shows the modification of the heater used in an Example. It is a graph which shows the experimental data at the time of applying this invention compared with a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wafer 2, 3 Capacitance 10 Stage 11 Conductive chuck 12 Insulation member 13 Back plate 14 Electrical shield member 15, 30 Heater 20 Tester 21 Signal processing part 24 Base measurement terminal 25, 26 Switch 41 Probe

Claims (3)

A capacity measuring system comprising a stage for mounting and fixing a wafer, and a tester, and measuring the capacity formed by using the back surface of the wafer as one electrode, with the tester,
The stage is
A conductive chuck on which the back surface of the wafer is placed;
An electrical shield member provided under the conductive chuck and insulated from the surroundings;
A back plate that supports the conductive chuck and the electrical shield member;
The tester is
A first measurement terminal to which a probe that contacts an electrode is connected to the surface of the wafer;
A base measurement terminal connected to the conductive chuck;
A measurement ground terminal for connecting the electrical shield member to the measurement ground;
The capacitance measuring system, wherein the capacitance is measured in a state where the electrical shield member is connected to the measurement ground. The stage further includes an insulating member that supports a bottom surface of the conductive chuck,
The capacity measurement system according to claim 1, wherein the back plate is made of a conductive material and supports the insulating member. A capacity measuring method for measuring a capacity formed by using the back surface of the wafer as one electrode,
Place and fix the wafer on a conductive chuck electrically insulated from other parts,
A probe of a tester is brought into contact with the electrode on the surface of the wafer,
Connecting the conductive chuck to a base measurement terminal of the tester;
An electrical shield member provided on the lower side of the conductive chuck is connected to the measurement ground of the tester,
A capacity measuring method comprising measuring the capacity.

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