JPH0735785A - Signal waveform measuring instrument - Google Patents

Abstract

PURPOSE:To provide a signal waveform measuring instrument which can improve measurement sensitivity for the signal waveform measuring instrument which can measure the electrical signal waveform of an electronic element especially utilizing electrooptical effect. CONSTITUTION:In a signal waveform measuring instrument which includes an electronic element 10, an electrooptical crystal body 14 whose refractive index changes when a voltage generated at the electronic element 10 is applied, and a sensor head part 20 which applies laser beams to the electrooptical crystal body 14 and then receives laser beams reflected from the electrooptical crystal body 14, and then detects the change in polarization state of reflection laser beams from the electrooptical crystal body 14 to measure the signal waveform of the electronic element 10, a phase shifter 48 is laid out on the optical path between the sensor head part 20 and the electrooptical crystal body 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal waveform measuring apparatus, and more particularly to a signal waveform measuring apparatus capable of measuring an electric signal waveform of an electronic element by utilizing an electro-optical effect.

In manufacturing and utilizing a semiconductor device such as an LSI, it is necessary to accurately measure signal waveforms inside and outside the device.
It is indispensable. However, with the recent increase in the speed of elements, it has become difficult to perform accurate measurement by an electric measurement method using a conventional LSI tester or the like.
Therefore, an optical signal waveform measuring method using the electro-optical effect of the semiconductor element substrate crystal has been proposed, and it has been confirmed that this method can measure a high-speed signal. (For example, JAValdmanis and G. Mourou “Subpicos
econd electronics sampling: principles and applica
tion ”IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL.QB-2
2, pp.69-78 etc.).

[0003]

2. Description of the Related Art FIG. 4 shows a block circuit of a conventional signal waveform measuring apparatus. In FIG. 4, the LS as an electronic element
A voltage is generated by the LSI drive circuit 12 at the terminal of I10. An electro-optical crystal body 14 is arranged adjacent to the LSI 10, and the LSI 10 of the electro-optical crystal body 14 is arranged.
A plurality of electrodes 16 are provided on the side, and each electrode 16
Has a function of reflecting laser light and
It has a function of applying the voltage generated at the terminal 10 to the electro-optic crystal body 14. LSI in the electro-optic crystal body 14
A transparent electrode plate 18 is provided on the side opposite to 10, and the transparent electrode plate 18 is connected to the ground potential. In the above configuration, when a voltage is generated at the terminal of the LSI 10 and this voltage is applied to the electro-optical crystal body 14 via the electrode 16, the voltage is transmitted through the electro-optical crystal body 14 according to the terminal voltage of the LSI 10. The polarization state of the laser light changes.

A sensor head portion 20 is provided for irradiating the electro-optical crystal body 14 with laser light and receiving reflected laser light from the electro-optical crystal body 14. In the sensor head portion 20, the laser light from the light source 22 passes through the beam splitter 24, is reflected by the mirror 26 and the scanning mirror 28a of the optical scanning mechanism 28, passes through the lens 30, and is transmitted through the transparent electrode plate 18 and the electro-optical device. It is transmitted through the crystal 14 and reflected by the electrode 16.

As described above, since the refractive index of the electro-optic crystal body 14 changes according to the terminal voltage of the LSI 10, the polarization state of the laser light passing through the electro-optic crystal body 14 changes. To do. The reflected laser light whose polarization state has changed passes through the transparent electrode 18 and the lens 30,
The light is reflected by the optical scanning mirror 28 a and the mirror 26, reflected by the reflecting surface 24 a of the beam splitter 24 in the sensor head unit 20, and directed toward the polarization beam splitter 32. The reflected laser light is separated into P and S polarized components by the polarized beam splitter 32, received by the photodetectors 34 and 36, respectively, and converted into electric signals.

The electric signals from the photodetectors 34 and 36 are supplied to a differential amplifier 38 to obtain the differential signal, and the differential signal is A / D converted by an A / D converter 40, It is supplied to the signal processing unit 42. In the signal processing unit 42, the A / D
The terminal voltage and signal waveform of the LSI 10 are measured based on the converted differential signal. Since the LSI 10 has many input / output terminals, when measuring the voltage of each terminal, the optical scanning mirror 28a is rotated as shown by the arrow so that the laser beam corresponds to the desired terminal. 14 electrodes 16
To be incident on.

The LSI drive mechanism 12 and the signal processing unit 4
2, a timing generator 44 that controls the light source 22 and emits a laser pulse synchronized with the LSI drive signal is controlled by the control unit 46.

[0008]

By the way, since a plurality of optical elements are used in the signal waveform measuring apparatus, the polarization state of the laser light changes by passing through these optical elements. Further, when the LSI terminal to be measured is selected by the optical scanning mechanism, since the incident angle of the light to the optical scanning mirror is not vertical, the reflectance differs for the P and S polarized components,
The polarization state changes.

As described above, when the polarization state of the laser light changes due to the optical element and the optical scanning mechanism, the voltage measurement sensitivity due to the electro-optical effect of the electro-optical crystal body is lowered. Further, conventionally, the sensor head is rotated to adjust the angle between the sensor head and the induced crystal axis of the electro-optic crystal so that the measurement sensitivity is maximized. However, since it is not possible to eliminate the change in the polarization state of the laser light quantity due to the optical element and the optical scanning mechanism, improvement in measurement sensitivity cannot be expected. That is, as shown in the graph of FIG. 5, the actual value of the measurement sensitivity was lower than the theoretical value (when there is no change in the polarization state due to the optical element or the optical scanning mechanism).

Therefore, an object of the present invention is to provide a signal waveform measuring device capable of improving the measurement sensitivity.

[0011]

In the present invention, an electronic element 10, an electro-optical crystal body 14 whose refractive index changes when a voltage generated in the electronic element 10 is applied, and an electro-optical crystal body 14 are provided. A sensor head section 20 for irradiating the laser beam and receiving the laser beam reflected by the electro-optical crystal body 14; and detecting a change in the polarization state of the reflected laser beam from the electro-optical crystal body 14. As a result, in the signal waveform measuring device for measuring the signal waveform of the electronic element 10, the phase shifter 48 is arranged on the optical path between the sensor head portion 20 and the electro-optic crystal body 14. And

[0012]

In the present invention, the phase shifter 48 is arranged on the optical path between the sensor head portion 20 and the electro-optic crystal body 14, and the phase shifter 48 causes an optical element and a laser by an optical scanning mechanism. Prevents changes in the polarization state of light.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block circuit of a signal waveform measuring apparatus according to an embodiment of the present invention. Note that, in FIG. 1, the same reference numerals as those of the conventional device of FIG.

In FIG. 1, the sensor head portion 20 and the mirror 2 are shown.
A phase shifter 48 is provided on the optical path between the
Hereinafter, the operation of the phase shifter 48 will be described. When the laser light is emitted from the light source 22, it is circularly polarized by the quarter-wave plate, and the beam splitter 24, the mirror 26, and the optical scanning mechanism 2
8. The electro-optic crystal body 14 is irradiated through the lens 30. If the polarization state of the laser light does not change when passing through the optical element or the optical scanning mechanism, the polarization state of the laser light is kept circularly polarized. Therefore, only the change of the polarization state due to the electro-optic effect of the electro-optic crystal body 14 can be detected, and the maximum measurement sensitivity can be obtained. However, in practice, the laser light incident on the electro-optical crystal body 14 is changed to elliptically polarized light, so that as shown in FIG. Even if the angle is adjusted, the measurement sensitivity cannot be improved.

Therefore, the phase shifter 48 having an appropriate amount of phase shift
Is inserted in the optical path between the sensor head portion 20 and the electro-optic crystal body 14. By inserting the phase shifter 48,
The polarization state of the laser light incident on the electro-optic crystal body 14 approaches circular polarization, and the measurement sensitivity is improved. That is, as shown in the graph of FIG. 2, the measurement sensitivity is improved by providing the phase shifter as compared with the case without the phase shifter.

The phase shifter 48 is a fixed phase shift amount (for example, a quarter wavelength plate), and the phase shifter 48 can be rotated by a rotating mechanism (not shown) as shown by an arrow. And
As shown in the graph of FIG. 3, when the phase shifter 48 is rotated, the measurement sensitivity changes. Therefore, the phase shifter 48 is rotated to the optimum azimuth angle so that the measurement sensitivity is maximized. Set.

Next, the structure for setting the phase shifter 48 to the optimum azimuth will be described. The measurement result obtained by the signal processing unit 42 is supplied to the measurement sensitivity detection circuit 50, the measurement sensitivity is obtained in the detection circuit 50, and the measurement sensitivity is supplied to the azimuth angle setting circuit 52 via the control unit 46. It
The azimuth angle setting circuit 52 finds each optimum azimuth of the phase shifter 48 that maximizes the measurement result, and rotates the phase shifter 48 to set the optimum azimuth angle, whereby the maximum measurement sensitivity is obtained. .

According to the above-described embodiment of the present invention, since the phase shifter is provided, it is possible to prevent the polarization state of the laser beam from changing due to the optical element and the optical scanning mechanism and to prevent the measurement sensitivity from lowering. As a result, the measurement sensitivity of the signal waveform measuring device can be improved.

In the above embodiment, the quarter wave plate is used as the phase shifter, but the phase shifter having another phase shift amount can also be used. Further, in the embodiment, the phase shifter with the fixed amount of phase shift is used, but the phase shifter with the variable amount of phase shift can also be implemented. Further, in the embodiment, the phase shifter is rotated to obtain the maximum sensitivity, but the phase shifter may be tilted to obtain the maximum sensitivity.

[0020]

As described above, according to the present invention, since the phase shifter is arranged on the optical path between the sensor head portion and the electro-optic crystal body, the laser beam by the optical element and the optical scanning mechanism is arranged. It is possible to improve the measurement sensitivity by preventing the change of the polarization state of.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a signal waveform measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing a change in measurement sensitivity due to a change in an angle between a sensor head portion and an induced crystal axis of an electro-optic crystal body in a measuring apparatus according to an embodiment of the present invention.

FIG. 3 is a graph showing a change in measurement sensitivity due to a change in azimuth angle of the phase shifter.

FIG. 4 is a block circuit diagram of a conventional signal waveform measuring device.

FIG. 5 is a graph showing a change in measurement sensitivity due to a change in an angle between a sensor head portion and an induced crystal axis of an electro-optic crystal body in a conventional measuring device.

[Explanation of symbols]

 10 ... LSI 14 ... Electro-optic crystal 20 ... Sensor head 48 ... Phase shifter

Claims (4)

[Claims] 1. An electronic device (10) and the electronic device (1)
0), the refractive index of which changes when an applied voltage is applied to the electro-optical crystal body (14), and the electro-optical crystal body (14).
A sensor head part (20) for irradiating a laser beam onto the laser beam and receiving the laser beam reflected by the electro-optic crystal body (14).
And a signal waveform measuring device for measuring a signal waveform of an electronic element (10) by detecting a change in a polarization state of reflected laser light from the electro-optic crystal body (14). Section (20) and electro-optic crystal (14)
A signal waveform measuring device characterized in that a phase shifter (48) is arranged on the optical path between and. 2. The signal waveform measuring apparatus according to claim 1, wherein the phase shifter (48) has a fixed amount of phase shift. 3. The signal waveform measuring device according to claim 2, wherein the phase shifter (48) is a quarter wavelength plate or a half wavelength plate. 4. The signal waveform measuring device according to claim 1, further comprising a rotating mechanism that rotates the phase shifter (48), wherein the rotating mechanism has a maximum measurement sensitivity. The signal waveform measuring device characterized in that the phase shifter (48) is rotated so as to set the optimum azimuth angle.