JP2012242157A - Device for inspecting semiconductor sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for inspecting a semiconductor sample capable of surely suppressing generation of noise due to fluctuation in a potential difference between ground of the semiconductor sample and ground of an electrical characteristics measuring means even when the fluctuation in the potential difference occurs.SOLUTION: A device IE1 for inspecting a semiconductor sample includes: a constant voltage source 9 which applies a constant voltage to the semiconductor sample S; an electrical characteristic measurement part 11 which measures electrical characteristics of the semiconductor sample S; and a reverse phase adder 33 in which a signal inputted into the electrical characteristic measurement part 11 is added to a reversed potential difference between ground of the semiconductor sample S (sample ground G1) connected to an external power supply device 41 and ground of the constant voltage source 9 (detection circuit ground G2).

Description

  The present invention relates to a semiconductor sample inspection apparatus, and more particularly, to a semiconductor sample inspection apparatus using an OBIRCH (Optical Beam Induced Resistance Change) method.

  A semiconductor that scans and irradiates a semiconductor sample connected to an external power supply device with a laser beam, measures changes in the electrical characteristics of the semiconductor sample associated with the laser beam irradiation, and inspects defects in the semiconductor sample based on the electrical characteristics change A sample inspection apparatus is known (see, for example, Patent Document 1). A semiconductor sample inspection apparatus described in Patent Document 1 includes a power source that applies a constant voltage to a semiconductor sample, and an electrical characteristic measurement unit that measures electrical characteristics of the semiconductor sample.

JP-A-6-300824

  However, the semiconductor sample inspection apparatus described in Patent Document 1 has the following problems.

  In a semiconductor sample inspection apparatus using the OBIRCH method, an inspection may be performed in a state where the semiconductor sample is operated. In this case, the inspection is performed with an external power supply device (for example, a semiconductor element tester, a stabilized power supply, a function generator, or a pulse generator) connected to the semiconductor sample. As a result of the investigation by the inventors, in the state where the external power supply device described above is connected to the semiconductor sample, fluctuation occurs in the potential difference between the ground of the semiconductor sample and the ground of the electrical property measuring means, and this potential difference It has been newly found that fluctuations are mixed in the electrical characteristic measuring means as noise.

  The semiconductor sample and the electrical property measuring means are electrically connected by a signal line. The ground of the semiconductor sample and the ground of the electrical characteristic measuring means are separated by the influence of the impedance of the signal line. For this reason, the ground noise of the external power supply device is mixed into the electrical characteristic measuring means through the impedance of the semiconductor sample. The mixing of the ground noise of the external power supply device becomes the above-described fluctuation of the potential difference and is mixed into the electrical characteristic measuring means. When the semiconductor sample and the electrical property measuring means are connected by a coaxial cable of the metric order, a fluctuation of about several μV may occur in the potential difference between the ground of the semiconductor sample and the ground of the electrical property measuring means. found.

  Fluctuations in the potential difference between the ground of the semiconductor sample and the ground of the electrical property measuring means can be suppressed by making each ground of the semiconductor sample, the electrical property measuring means, and the external power supply device common. However, since the impedance of the signal line connecting the semiconductor sample and the electrical property measuring means exists, the above-described fluctuation of the potential difference still remains. Further, even when the grounds of the semiconductor sample, the electrical characteristic measuring means, and the external power supply device are shared, it is impossible to make these ground potentials the same. In particular, the external power supply device and the semiconductor sample inspection device are generally configured separately, and the ground is generally set independently.

  In order to suppress the influence of noise due to the above-described fluctuation of the potential difference, it is conceivable to lengthen the measurement time and average the fluctuation of the potential difference. However, in this case, there is a possibility that the turnaround time (TAT) of the inspection process becomes longer due to the longer measurement time. It is also conceivable to improve the S / N ratio by increasing the intensity of the laser beam applied to the semiconductor sample and suppress the influence of noise caused by the above-described fluctuation of the potential difference. However, in this case, since the intensity of the laser beam is high, the semiconductor sample may be destroyed.

  The present invention is an inspection of a semiconductor sample that can reliably suppress the generation of noise due to the fluctuation of the potential difference even when the potential difference between the ground of the semiconductor sample and the ground of the electrical property measuring means fluctuates. An object is to provide an apparatus.

  The present invention scans and irradiates a semiconductor sample connected to an external power supply device with a laser beam, measures a change in electrical characteristics of the semiconductor sample accompanying the irradiation of the laser beam, and based on the change in electrical characteristics, A semiconductor sample inspection apparatus for inspecting a defective portion, including a power source for applying a constant voltage or supplying a constant current to a semiconductor sample, an electrical property measuring unit for measuring electrical properties of the semiconductor sample, and an electrical property measuring unit Reverse phase addition that adds the potential difference between the ground of the semiconductor sample connected to the external power supply and the ground of the power source to either one of the input signal and the signal output from the electrical characteristic measuring means in the reverse phase And means.

  In the semiconductor sample inspection apparatus according to the present invention, the antiphase addition means is connected to the external power supply apparatus to one of the signal input to the electrical characteristic measurement means and the signal output from the electrical characteristic measurement means. The potential difference between the ground of the semiconductor sample to be grounded and the ground of the power source is reversed and added. Thereby, even when fluctuations occur in the potential difference between the ground of the semiconductor sample and the ground of the electrical characteristic measuring means, the fluctuation of the potential difference is canceled, and the generation of noise can be reliably suppressed.

  In the present invention, the occurrence of noise is suppressed by canceling the fluctuation of the potential difference between the ground of the semiconductor sample and the ground of the electrical property measuring means. Therefore, it is not necessary to set a long measurement time in order to suppress the influence of noise, and it is not necessary to increase the intensity of the laser beam.

  The power source is a constant voltage source that applies a constant voltage, the electrical characteristic measuring means has a current-voltage converter that converts an input current signal into a voltage signal, and the negative phase adding means is a current-voltage converter It may be provided in the previous stage. In this case, even when a constant voltage source is used as the power source, the current change can be measured as the electrical characteristic change of the semiconductor sample while suppressing the influence of noise. Since the anti-phase addition means is provided in the previous stage of the current-voltage converter, the above-described fluctuation of the potential difference is canceled before the signal is amplified by the current-voltage converter, and the generation of noise is more reliably suppressed. can do.

  The power source is a constant current source that supplies a constant current, the electrical characteristic measuring means has a voltage amplifier that amplifies and outputs the input voltage signal, and the anti-phase addition means is provided in front of the voltage amplifier. It may be. In this case, even when a constant current source is used as a power source, it is possible to measure a voltage change as an electrical characteristic change of the semiconductor sample while suppressing the influence of noise. Since the anti-phase addition means is provided in the front stage of the voltage amplifier, the above-described fluctuation of the potential difference is canceled before the signal is amplified by the voltage amplifier, and the generation of noise can be suppressed more reliably. .

  The negative phase addition means includes a negative phase amplifier that reverses the potential difference between the ground of the semiconductor sample connected to the external power supply device and the ground of the power source, and an adder that adds the outputs from the negative phase amplifier. It may be. In this case, the configuration of the anti-phase addition means for adding the potential difference between the ground of the semiconductor sample connected to the external power supply device and the ground of the power source in the reverse phase can be realized easily and at low cost.

  According to the present invention, even when fluctuation occurs in the potential difference between the ground of the semiconductor sample and the ground of the electrical property measuring means, the semiconductor sample that can reliably suppress the generation of noise due to the fluctuation of the potential difference. An inspection apparatus can be provided.

It is a schematic block diagram which shows the structure of the test | inspection apparatus of the semiconductor sample which concerns on this embodiment. It is the schematic for demonstrating a semiconductor sample, an addition part, and a current-voltage conversion part. It is a schematic block diagram which shows the structure of the test | inspection apparatus of the semiconductor sample which concerns on the modification of this embodiment. It is the schematic for demonstrating a semiconductor sample, an addition part, and a voltage amplification part.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  With reference to FIGS. 1 and 2, the configuration of the semiconductor sample inspection apparatus IE1 according to the present embodiment will be described. FIG. 1 is a schematic block diagram showing a configuration of a semiconductor sample inspection apparatus according to the present embodiment. FIG. 2 is a schematic diagram for explaining a semiconductor sample, an antiphase addition unit, and a current-voltage conversion unit.

  The semiconductor sample inspection apparatus IE1 is an inspection apparatus using the OBIRCH method. As shown in FIG. 1, the laser generation source 1, the laser scanning unit 3, the microscope 5, the sample stage 7, the constant voltage source 9, A characteristic measurement unit 11, a system control unit 13, and a monitor 15 are provided.

  The laser source 1 generates and emits laser light. The laser scanning unit 3 is disposed on the optical path of the laser light emitted from the laser generation source 1 and receives the laser light. The laser scanning unit 3 scans the incident laser light in a predetermined direction. For example, the laser scanning unit 3 performs a raster scan in a two-dimensional direction orthogonal to the incident direction. The microscope 5 focuses the scanned laser light on a minute spot diameter. On the sample stage 7, a semiconductor sample S (for example, a semiconductor integrated circuit) is placed. The semiconductor sample S placed on the sample stage 7 is positioned at the focal position of the microscope 5.

The constant voltage source 9 applies a predetermined constant voltage to the semiconductor sample S. The constant voltage source 9 is connected to the sample stage 7 via the signal line 21 and is electrically connected to the power supply terminal of the semiconductor sample S through the wiring of the sample stage 7. Ground terminal S _G of the placed semiconductor sample S on the sample stage 7, the ground line 7a and the ground terminal 7b of the sample table 7 and is electrically connected to the ground terminal of the constant voltage source 9 via a ground line 23 ing.

Ground terminal S _G of the semiconductor sample S via the ground wiring 7a and the ground terminal 7c of the sample table 7 and is connected to the ground of the sample table 7 (sample ground) G1. The constant voltage source 9 is connected to the ground (detection circuit ground) G2.

  The electrical property measurement unit 11 measures electrical properties of the semiconductor sample S. In the present embodiment, current is measured as the electrical characteristics of the semiconductor sample S. The electrical characteristic measuring unit 11 is connected to the sample stage 7 through a signal line 25 and is electrically connected to a predetermined terminal of the semiconductor sample S through the wiring of the sample stage 7. For example, a coaxial cable is used as the signal line 25. As shown in FIG. 2, one end side of the outer conductor (shield layer) of the coaxial cable (signal line 25) is connected to the sample ground G1, and the other end side of the outer conductor of the coaxial cable is connected to the detection circuit ground. Connected to G2.

  As shown in FIG. 2, the electrical characteristic measurement unit 11 has a current-voltage converter 31. The current / voltage converter 31 amplifies the input current signal and then converts it into a voltage signal. The electrical characteristic measuring unit 11 (current / voltage converter 31) is connected to the ground (detection circuit ground) G2 in the same manner as the constant voltage source 9.

  The system control unit 13 is connected to the laser scanning unit 3, the constant voltage source 9, and the electrical characteristic measurement unit 11 via a control line 27. The system control unit 13 is also connected to the monitor 15.

In the present embodiment, an external power supply device 41 is connected to the inspection apparatus IE1. The external power supply device 41 is for bringing the semiconductor sample S into a desired operation state, is connected to the sample stage 7 through the signal line 43, and is electrically connected to a predetermined terminal of the semiconductor sample S through the wiring of the sample stage 7. Connected. Ground terminal S _G of the placed semiconductor sample S on the sample stage 7, the ground line 7a and the ground terminal 7d of the sample stage 7, and through a ground line 45, electrically connected to the ground terminal of the external power supply device 41 Has been. The external power supply device 41 is connected to the ground (external power supply device ground) G3. As the external power supply device 41, for example, a semiconductor element tester such as an LSI tester, a stabilized power supply, a function generator, or a pulse generator is used.

  In the inspection apparatus IE1, the laser beam emitted from the laser source 1 is scanned by the laser scanning unit 3 and condensed by the microscope 5, and is irradiated onto a fine portion of the surface of the semiconductor sample S as a laser beam. Scanning by the laser scanning unit 3 is controlled by the system control unit 13.

  A predetermined voltage is applied to the semiconductor sample S by the constant voltage source 9, and a predetermined current flows in the circuit of the semiconductor sample S. In the part irradiated with the laser beam in the semiconductor sample S, the temperature rises and the resistivity changes with the absorption of the laser beam. For this reason, the value of the current flowing through the semiconductor sample S changes. In places where there are defects such as voids, heat conduction is poor. Therefore, when a laser beam is irradiated to such a place, the heat does not easily escape to the surroundings, and the temperature rise is large at the place where there is a defect. Thereby, in the defective part of the semiconductor sample S to which a predetermined voltage is applied, the change in resistivity increases as the temperature rises, and the change in current value is also large.

  In the electrical characteristic measuring unit 11 (current-voltage converter 31), the detected current is once amplified and then converted into a voltage. A detection signal (voltage signal) corresponding to the converted voltage value is sent from the current-voltage converter 31 to the system control unit 13. The system control unit 13 sequentially converts the voltage value difference obtained as the detection signal into luminance information, and displays the image information arranged in accordance with the laser beam irradiation position on the monitor 15. Thereby, the defect location of the semiconductor sample S can be confirmed with an image. The lengths of the signal line 21, the ground line 23, and the signal line 25 are, for example, 1 m or more.

  The configuration and operation of an inspection apparatus using the OBIRCH method are known in the art (for example, described in Patent Document 1 described above and International Publication No. 2004/065972 by the applicant of the present application). Further detailed description will be omitted.

  By the way, the inspection apparatus IE1 according to the present embodiment includes a reversed-phase addition unit 33 as shown in FIGS. The negative phase adder 33 includes a negative phase amplifier 35 and an adder 37, and is provided in the previous stage of the current-voltage converter 31.

  In the negative phase amplifier 35, the sample ground G1 is connected to the inverting input terminal, and the detection circuit ground G2 is connected to the non-inverting input terminal. That is, the negative phase amplifier 35 receives the ground voltage of the semiconductor sample S and the ground voltage of the constant voltage source 9. The negative phase amplifier 35 amplifies the potential difference between the ground voltage of the semiconductor sample S and the ground voltage of the constant voltage source 9 and outputs it as a negative phase.

  The adder 37 is inserted in the signal line 25. As a result, the output from the negative phase amplifier 35 is added to the signal input to the current-voltage converter 31. That is, the potential difference between the ground voltage of the semiconductor sample S and the ground voltage of the constant voltage source 9 is reversed by the signal input to the current-voltage converter 31 by the anti-phase adder 33 (the anti-phase amplifier 35 and the adder 37). Phases will be added.

  As described above, in the present embodiment, fluctuation (for example, fluctuation of about several μV) occurs in the potential difference between the sample ground G1 of the semiconductor sample S and the detection circuit ground G2 of the electrical characteristic measurement unit 11 (current / voltage converter 31). ) Occurs, the fluctuation of the potential difference is canceled by the anti-phase adder 33 (the anti-phase amplifier 35 and the adder 37). As a result, in the inspection apparatus IE1, it is possible to reliably suppress the occurrence of noise due to the above-described potential difference fluctuation.

  And in this embodiment, generation | occurrence | production of noise is generated by canceling the fluctuation of the potential difference between the sample ground G1 of the semiconductor sample S and the detection circuit ground G2 of the electrical characteristic measuring unit 11 (current-voltage converter 31). It is suppressed. Therefore, in the inspection apparatus IE1, it is not necessary to set a long measurement time in order to suppress the influence of noise, and it is not necessary to increase the intensity of the laser beam.

  In the present embodiment, the inspection apparatus IE1 includes a constant voltage source 9 as a power source, the electrical characteristic measurement unit 11 includes a current-voltage converter 31, and an anti-phase addition unit 33 (adder 37) includes the current-voltage converter 31. It is provided in the previous stage. Thereby, first, even when the constant voltage source 9 is used as the power source, the inspection apparatus IE1 can measure the current change as the electrical characteristic change of the semiconductor sample S while suppressing the influence of noise. And since the antiphase addition part 33 (adder 37) is provided in the front | former stage of the current-voltage converter 31, before the signal is amplified in the current-voltage converter 31, the fluctuation | variation of the above-mentioned potential difference is canceled. It will be. As a result, in the inspection apparatus IE1, the generation of noise due to the above-described fluctuation of the potential difference can be more reliably suppressed.

  In the present embodiment, the anti-phase addition unit 33 includes an anti-phase amplifier 35 and an adder 37. Thereby, the structure of the anti | reverse | negative phase addition part 33 is realizable with simple and low cost.

  Next, the configuration of the semiconductor sample inspection apparatus IE2 according to the modification will be described with reference to FIGS. FIG. 3 is a schematic block diagram showing a configuration of a semiconductor sample inspection apparatus according to a modification. FIG. 4 is a schematic diagram for explaining a semiconductor sample, an antiphase addition unit, and a current-voltage conversion unit.

  The inspection apparatus IE2 according to the modified example is also an inspection apparatus using the OBIRCH method, and as shown in FIG. 3, the laser source 1, the laser scanning unit 3, the microscope 5, the sample stage 7, the constant current source 51, An electrical characteristic measurement unit 11, a system control unit 13, a monitor 15, and a reverse phase addition unit 33 are provided. As shown in FIG. 3, the inspection apparatus IE <b> 2 includes a constant current source 51 that supplies a predetermined constant current instead of the constant voltage source 9. As shown in FIG. 4, the electrical characteristic measurement unit 11 includes a voltage amplifier 53 instead of the current-voltage converter 31. The inspection apparatus IE2 is different from the inspection apparatus IE1 in that a voltage change is measured as a change in electrical characteristics of the semiconductor sample S accompanying laser beam irradiation, and a defective portion of the semiconductor sample S is inspected based on the voltage change.

  Also in this modification, even when a fluctuation occurs in the potential difference between the sample ground G1 of the semiconductor sample S and the detection circuit ground G2 of the electrical characteristic measurement unit 11 (current / voltage converter 31), the fluctuation of the potential difference is in reverse phase. It will be canceled by the adder 33 (reverse phase amplifier 35 and adder 37). As a result, in the inspection apparatus IE2, it is possible to reliably suppress the occurrence of noise due to the above-described potential difference fluctuation. Also in the inspection apparatus IE2, it is not necessary to set a long measurement time in order to suppress the influence of noise, and it is not necessary to increase the intensity of the laser beam.

  In the present embodiment, the inspection apparatus IE2 includes a constant current source 51 as a power source, the electrical characteristic measurement unit 11 includes a voltage amplifier 53, and a negative phase addition unit 33 (adder 37) is provided upstream of the current-voltage converter 31. Is provided. Thereby, first, even when the constant current source 51 is used as a power source, the inspection apparatus IE2 can measure a current change as an electrical characteristic change of the semiconductor sample S while suppressing the influence of noise. And since the anti-phase addition part 33 (adder 37) is provided in the front | former stage of the voltage amplifier 53, before a signal is amplified in the current voltage converter 31, the fluctuation | variation of the above-mentioned potential difference is cancelled. Become. As a result, also in the inspection apparatus IE2, generation of noise due to the above-described fluctuation of the potential difference can be more reliably suppressed.

  The preferred embodiments of the present invention have been described above. However, the present invention is not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

In the present embodiment and the modification, the voltage of the sample ground G1 is input to the negative phase adder 33 (the negative phase amplifier 35) as the ground voltage of the semiconductor sample S connected to the external power supply device 41. Not limited to. For example, the semiconductor as the voltage of the ground sample S, the ground terminal S _G of the voltage may be input directly to the reverse phase addition section 33 (reverse phase amplifier 35), a ground voltage terminal 7b~7d reverse phase addition section 33 It may be directly input to (the negative phase amplifier 35).

  In the present embodiment and the modification, the anti-phase addition unit 33 (adder 37) is provided in the previous stage of the current-voltage converter 31, but the present invention is not limited to this. For example, the anti-phase addition unit 33 (adder 37) may be provided at the subsequent stage of the current-voltage converter 31. However, it is preferable that the anti-phase addition unit 33 (adder 37) is provided in the previous stage of the current-voltage converter 31 in order to more reliably suppress the generation of noise.

  The present invention can be used in a semiconductor sample inspection apparatus using the OBIRCH method.

  DESCRIPTION OF SYMBOLS 1 ... Laser generating source, 3 ... Laser scanning part, 5 ... Microscope, 7 ... Sample stand, 7b-7d ... Ground terminal, 9 ... Constant voltage source, 11 ... Electrical property measuring part, 13 ... System control part, 25 ... Signal Line 31, current-voltage converter, 33, reverse phase adder, 35, reverse phase amplifier, 37, adder, 41, external power supply, 51, constant current source, 53, voltage amplifier, G 1, sample ground, G 2 ... detection circuit ground, G3 ... external power supply device ground, IE1, IE2 ... inspection device, S ... semiconductor sample.

Claims (4)

A semiconductor sample connected to an external power supply device is scanned and irradiated with a laser beam, a change in electrical characteristics of the semiconductor sample due to the irradiation of the laser beam is measured, and a defect portion of the semiconductor sample is inspected based on the change in electrical characteristics An inspection apparatus for semiconductor samples,
A power source for applying a constant voltage or supplying a constant current to the semiconductor sample;
Electrical property measuring means for measuring electrical properties of a semiconductor sample;
The potential difference between the ground of the semiconductor sample connected to the external power supply device and the ground of the power source is reversed to one of the signal input to the electrical property measuring means and the signal output from the electrical property measuring means. And an anti-phase addition means for adding in phase. The power source is a constant voltage source for applying a constant voltage;
The electrical characteristic measuring means has a current-voltage converter that converts an input current signal into a voltage signal,
The semiconductor sample inspection apparatus according to claim 1, wherein the negative-phase addition unit is provided in a stage preceding the current-voltage converter. The power source is a constant current source for supplying a constant current;
The electrical characteristic measuring means has a voltage amplifier that amplifies and outputs an input voltage signal,
The semiconductor sample inspection apparatus according to claim 1, wherein the negative phase addition means is provided in a stage preceding the voltage amplifier.   The negative phase addition means, a negative phase amplifier that reverses the potential difference between the ground of the semiconductor sample connected to an external power supply device and the ground of the power source, and an adder that adds outputs from the negative phase amplifier; The semiconductor sample inspection apparatus according to claim 1, wherein the semiconductor sample inspection apparatus includes:

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