JPH0735827A - Electrooptical measuring apparatus - Google Patents

Abstract

PURPOSE:To enable highly accurate positioning control by irradiating a probe supported on a cantilever with light to detect and control the position, of the probe from the reflected light thereof. CONSTITUTION:A part to be measured of a subject 20 set on a piezo-electric element 8 is set near a probe 1 by the operation from a probe position operating section 6. Subsequently, the probe 1 is brought into contact with the subject 20 to scan. light irradiated from a light source 52 is reflected on the probe 1 to be incident into a photodetector 112. The irradiation position of the reflected light incident into the photo detector 112 changes according to changes in the position of the probe 1. The changes in the position are measured with a probe position detecting circuit 2 to detect the position of the probe 1. Since a cantilever 10 the same as that used in a scan type interatomic force microscope is used as holding part of the probe 1, less mass reduces a force working on the subject 20 and thus, there is little possibility of damaging the subject 20 physically.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention finds use in the research and manufacture of semiconductors. In particular, it relates to a technique for measuring an operating state of a high speed integrated electronic circuit.

[0002]

2. Description of the Related Art In recent years, the frequency of signals handled in the field of electronics has reached 250 GHz, and the means for observing these high-speed electrical waveforms cannot keep up with the technological progress at the present time. .
In addition, the miniaturization of elements is progressing, and not only the temporal resolution but also the spatial resolution of electrical measuring devices cannot keep up with the current technological progress.

In order to observe a high speed phenomenon such as a high speed operation state of a minute element, a sampling oscilloscope has conventionally been a typical one. Further, in recent years, EO sampling method utilizing the electro-optic effect of electro-optic crystal has been studied (EO sampling Takeshi Kamiya Ryo Takahashi.
Electro-Optical Sampling Using Semiconductor Laser as Light Source Applied Physics Vol. 61, No. 1, p30, 1992, T. Nagatsuma, "M
measurement of High-Speed Devices and Integrated Ci
rcuits Using Electro-Optic Sampling Technique "IEIC
E Trans. Electron., Vol.E-76C, no.1, January 1993.).

A conventional example will be described with reference to FIG. FIG. 8 is a block diagram of a conventional device. The site to be measured of the object to be measured 20 placed on the test table 30 is set near the probe 1 by operating the test table operating unit 32. Subsequently, the probe 1 is once brought into contact with the object 20 to be measured, and then the height adjustment section 3 formed of a piezo element or the like adjusts the height direction to determine the optimum measurement position. The light source 5 irradiates the probe 1 with light. If an electric potential exists at the measured portion of the object to be measured 20, the refractive index of the electro-optical crystal changes due to the electro-optical effect, and the polarization direction of the light emitted from the light source 5 is compared with that when the electric potential does not exist. Change. This amount of displacement is detected by an optical system including the wave plate 9, the polarizer 7, and the light receiving element 11. This displacement amount is input to the potential measuring device 12, and the potential of the measurement site is measured.

[0005]

In such a conventional apparatus, a probe is brought into contact with an object to be measured, such as an integrated circuit, whose thickness is not partially uniform, every time the measuring portion is changed, and positioning is performed. It is necessary to repeat the operation, it takes a long time to measure, the mass of the holding part of the probe is large,
There is a problem that the circuit of the device under test is likely to be physically damaged. As described above, in the conventional device, only the pursuit of the sampling speed is regarded as important and the position control is not considered so much.

The present invention has been made against such a background, and an object of the present invention is to provide an electro-optical measuring device capable of performing positioning control with high accuracy.

[0007]

According to the present invention, there is provided a probe, at least a part of which is formed of an electro-optic crystal and is brought close to an object to be measured, a first light source for irradiating the electro-optic crystal with light, and a first light source for irradiating the electro-optic crystal with light. Displacement amount detecting means for detecting the optical displacement amount of the electro-optical crystal from the reflected light of the light source that has passed through the electro-optical crystal, and means for measuring the potential of the measured object from the detection result of the displacement amount detecting means. It is an electro-optical measuring device provided with.

Here, a feature of the present invention is that the probe is supported by a cantilever, and a second light source for irradiating the probe with light and a reflected light of the probe of the second light source Position detecting means for detecting the position of the probe and means for controlling the position of the probe with respect to the object to be measured by using the detection result of the position detecting means as an input.

Further, position detecting means for detecting the position of the probe from the reflected light of the probe of the first light source, and the position of the probe with respect to the object to be measured are input by using the detection result of the position detecting means. It may be configured to include a means for performing.

The cantilever may be provided with a waveguide through which the light applied to the electro-optic crystal and / or the reflected light passes.

The probe may be provided with an electrode, and circuit means for connecting the electrode to a reference potential may be provided.

The probe includes a probe in contact with the object to be measured and an electro-optic crystal in proximity to the object to be measured, and a second light source for irradiating the upper surface of the probe with light.
Position detection means for detecting the position of the probe from the reflected light of the probe of the second light source, and means for controlling the position of the probe with respect to the object to be measured with the detection result of the position detection means as an input. It can also be configured.

[0013]

In the field of lasers, it has become relatively easy to obtain optical pulses in the sub-picosecond range, so this laser pulse is used for sampling electrical signals. As a result, it is possible to directly measure the potential at the point to be measured at a higher speed than conventional electronic measurement and without extracting the signal to the outside. It can be said that this method replaces the electrical pulse for sampling in the sampling oscilloscope with the optical pulse.

Regarding the position control of the probe, the fine positional displacement of the probe can be expressed as the displacement of the irradiation position of the reflected light of the light irradiated on the probe. The light receiving element detects the displacement of the irradiation position of the reflected light to detect the position of the probe. The probe displaces its position according to the unevenness of the surface of the object to be measured.

For an object to be measured having an unevenness such as an integrated circuit, the position of the probe with respect to the object to be measured can be highly accurately compared by comparing the condition of the unevenness known in advance with the condition of the unevenness scanned by the probe. Can be controlled with.

The light source for detecting the displacement amount and the light source for measuring the electro-optical effect of the electro-optical crystal can be the same light source. Further, the light receiving elements can be the same.

As a result, an electro-optical measuring device capable of highly accurate positioning control can be realized with a simple structure.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a first embodiment device of the present invention.

According to the present invention, at least a part of the probe 1 is made of an electro-optic crystal and is brought close to the object to be measured 20, and a first light source 51 for irradiating the electro-optic crystal with light.
And a light receiving element 111 as a displacement amount detecting means for detecting an optical displacement amount of the electro-optical crystal from the reflected light of the first light source 51 passing through the electro-optical crystal, and a displacement amount detection result of the light receiving element 111. Is an electro-optical measuring device including a potential measuring device 12 as a means for measuring the potential of the DUT 20.

Here, the feature of the present invention is that the probe 1 is supported by the cantilever 10, and the second light source 52 for irradiating the probe 1 with light and the second light source 5 are provided.
2 as the position detecting means for detecting the position of the probe 1 from the reflected light of the probe 1, and the object to be measured 20 of the probe 1 with the detection result of the probe position detecting circuit 2 as an input. The probe position control circuit 4 and the probe position operation unit 6 are provided as means for controlling the position with respect to.

Next, the operation of the first embodiment of the present invention will be described. The measurement target portion of the measurement target 20 installed on the piezo element 8 is operated by the probe position operation unit 6 and the probe 1 is operated.
Is set near. Subsequently, the probe 1 is brought into contact with the object to be measured 20 to perform scanning. The light emitted from the light source 52 is reflected by the probe 1 and enters the light receiving element 112. The irradiation position of the reflected light incident on the light receiving element 112 is displaced according to the positional displacement of the probe 1. The displacement amount is measured by the probe position detection circuit 2 to detect the position of the probe 1. In the first embodiment of the present invention, since the cantilever 10 similar to that used in the scanning atomic force microscope (AFM) is used as the holding portion of the probe 1, its mass is small and the force used for the object to be measured is also extremely small. Therefore, there is almost no possibility of physically damaging the DUT 20 as described in the conventional example.

The probe 1 performs scanning while detecting the unevenness of the surface of the object 20 to be measured, and the probe position control circuit 4
Performs positioning of the probe 1 while comparing with the map of the uneven state that has been input in advance. When the measurement position is determined, the light source 51 irradiates the probe 1 with light. If an electric potential exists at the measured portion of the object to be measured 20, the refractive index of the electro-optical crystal changes due to the electro-optical effect, and the polarization direction of the light emitted from the light source 51 is compared with that when the electric potential does not exist. Change. This displacement amount is detected by an optical system including the wave plate 9, the polarizer 7, and the light receiving element 111. This displacement amount is input to the potential measuring device 12, and the potential of the measurement site is measured. The light source 51 emits pulsed light. The light emission cycle of this pulsed light is the sampling cycle of optical sampling.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram of the apparatus of the second embodiment of the present invention. The second embodiment of the present invention is configured to detect the position of the probe 1 and measure the electro-optical effect with one light source 5 as compared with the device of the first embodiment of the present invention. The light receiving elements 111 and 112 are two-divided light receiving elements, the light receiving element 111 includes light receiving portions a and b, and the light receiving element 112 includes light receiving portions c and d. Assuming that the light receiving level of the light receiving section a is A, the light receiving level of the light receiving section b is B, the light receiving level of the light receiving section c is C, and the light receiving level of the light receiving section d is D, [A + D]-[B + C] is the position. It is used for detection, and [A + B]-[C + D] is used for potential detection of the DUT 20. The light source 5 emits pulsed light. Position detection also uses pulsed light and has no practical problem.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of the apparatus of the third embodiment of the present invention. The third embodiment of the present invention has a configuration using one light source 5 and one light receiving element 11 as compared with the device of the first embodiment of the present invention. The light receiving element 11 is a two-divided light receiving element and is composed of light receiving portions a and b. [A−B] is used for position detection and [A + B] is used for potential detection of the DUT 20.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram of the device of the fourth embodiment of the present invention. The fourth embodiment of the present invention has a structure in which the cantilever 10 is provided with an optical waveguide. The light emitted from the light source 5 may be directly incident on the waveguide of the cantilever 10 or may be incident via an optical fiber. That is, the light source 5
It is an advantage of providing the waveguide in the cantilever 10 that the installation position can be arbitrarily selected. The measurement principle is the same as that of the third embodiment of the present invention in which one light receiver 11 is provided.

Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram of the fifth embodiment of the present invention. The fifth embodiment of the present invention has a structure in which the cantilever 10 is provided with an optical waveguide as in the fourth embodiment of the present invention. The position is detected by the light receiving element 111, and the potential is detected by the light receiving element 112. The measurement principle is the same as that of the second embodiment of the present invention, but in the fifth embodiment of the present invention, the potential is detected by the light returning from the waveguide.

Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a block diagram of a sixth embodiment device of the present invention. The sixth embodiment of the present invention is the electro-optic crystal 62 and the probe 60.
The feature is that the probe 1 is composed of two parts. The probe 60 detects unevenness of the measured object 20. The position of the probe 60 is detected by the light source 52 and the light receiving element 1.
12 performed. The electro-optic crystal 62 is brought close to the measurement site of the measurement object 20 by the probe 60. The electro-optic crystal 62 produces an electro-optic effect according to the potential of the measurement site. The light from the light source 51 is reflected in the electro-optic crystal 62 a plurality of times and reaches the light receiving element 111 via the polarizer 7. That is, it is possible to measure a fine displacement that cannot be measured by one reflection by a plurality of reflections. Therefore, it is an advantage of the sixth embodiment of the present invention that it is possible to perform highly sensitive potential measurement.

Next, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 7 is a block diagram of the seventh embodiment device of the present invention. In the seventh embodiment of the present invention, as shown in FIG.
A ground electrode 70 is provided on the probe 1. Ground electrode 70
As shown in FIG. 7 (b), it has a shape in which a hole is formed at the center and does not hinder the irradiation of light. As a result, the DUT 20
The absolute value of the measured potential of can be measured. In the first to seventh embodiments of the present invention, all light reflecting portions are processed into a mirror surface or a half mirror.

[0029]

As described above, according to the present invention, an electro-optical measuring device capable of highly accurate positioning control can be realized with a simple structure.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a second embodiment device of the present invention.

FIG. 3 is a configuration diagram of an apparatus according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a fourth embodiment device of the present invention.

FIG. 5 is a configuration diagram of a fifth embodiment device of the present invention.

FIG. 6 is a configuration diagram of a sixth embodiment device of the present invention.

FIG. 7 is a configuration diagram of a seventh embodiment device of the present invention.

FIG. 8 is a configuration diagram of a conventional device.

[Explanation of symbols]

 1 probe 2 probe position detection circuit 3 height adjustment unit 4 probe position control circuit 5, 51, 52 light source 6 probe position operation unit 7, 71, 72 polarizer 8 piezo element 9 wave plate 10 cantilever 11, 111, 112 light receiving element 12 potential measuring device 20 object to be measured 30 test table 32 test table position operation unit 60 probe 62 electro-optic crystal 70 ground electrode a, b, c, d light receiving unit

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masao Kasahara 2-11-13 Nakamachi, Musashino-shi, Tokyo Inside Terratec Co., Ltd.

Claims (5)

[Claims] 1. A probe (1), at least a part of which is formed of an electro-optic crystal and is brought close to an object to be measured, a first light source (51) for irradiating the electro-optic crystal with light, and the first light source. The displacement amount detecting means (111) for detecting the optical displacement amount of the electro-optical crystal from the reflected light that has passed through the electro-optical crystal, and the potential of the measured object is measured from the detection result of the displacement amount detecting means. An electro-optical measuring device comprising means (12), the probe being supported by a cantilever (10), a second light source (52) for irradiating the probe with light, and a probe for the second light source. Position detecting means (112, 2) for detecting the position of the probe from the reflected light, and means (4) for controlling the position of the probe with respect to the object to be measured using the detection result of the position detecting means as an input. 8)
An electro-optical measuring device comprising: 2. A probe (1) at least a part of which is formed of an electro-optic crystal and which is brought close to an object to be measured, a first light source (51) for irradiating the electro-optic crystal with light, and a first light source of the first light source. The displacement amount detecting means (111) for detecting the optical displacement amount of the electro-optical crystal from the reflected light that has passed through the electro-optical crystal, and the potential of the measured object is measured from the detection result of the displacement amount detecting means. An electro-optical measuring device comprising means (12), wherein the probe is supported by a cantilever (10), and position detecting means (112, for detecting the position of the probe from reflected light of the probe of the first light source). 2) and means (4, 8) for controlling the position of the probe with respect to the object to be measured by using the detection result of the position detecting means as an input.
An electro-optical measuring device comprising: 3. The electro-optical measuring device according to claim 1, wherein the cantilever is provided with a waveguide through which the light irradiating the electro-optical crystal and / or the reflected light passes. 4. The probe according to claim 1, further comprising an electrode, and circuit means for connecting the electrode to a reference potential.
The electro-optical measurement device according to any one of claims. 5. A probe (1) at least a part of which is formed of an electro-optical crystal and is brought close to an object to be measured, a first light source (51) for irradiating the electro-optical crystal with light, and a first light source of the first light source (51). The displacement amount detecting means (111) for detecting the optical displacement amount of the electro-optical crystal from the reflected light that has passed through the electro-optical crystal, and the potential of the measured object is measured from the detection result of the displacement amount detecting means. An electro-optical measuring device comprising means (12), wherein the probe is supported by a cantilever (10) and is in contact with an object to be measured (60) and an electro-optical crystal (62) adjacent to the object to be measured. And a second light source (52) for irradiating the upper surface of the probe with light.
Position detecting means (112, 2) for detecting the position of the probe from the reflected light of the probe of the second light source, and the position of the probe with respect to the object to be measured with the detection result of the position detecting means as an input. Means for controlling (4, 8)
An electro-optical measuring device comprising: