JPH0572299A - Method and apparatus for measuring voltage signal of integrated circuit - Google Patents

Abstract

PURPOSE:To enable measurement of an absolute voltage necessary for comparison of waveforms and the amplitude of the waveforms by achieving higher reproducibility of the measurement. CONSTITUTION:A means is provided which makes a probe 1 approaches a circuit X to be measured until both contacts each other with a finely moving mechanism to determine a clearance between the two and positions the probe 1 by separating the two at a desired distance with the contact point thereof as reference and a means to detect a slight contact between the probe 1 and the circuit X to be measured at a high sensitive achieve a positioning at a high accuracy. First, a voltage signal with a low frequency known is inputted into an input or output of the circuit or a terminal for a power source with the circuit X to be measured not operated and a change in the intensity of light measured by irradiating the probe 1 with a laser light with the probe 1 contacting a wiring connected to the terminal and a change in the intensity of light measured by irradiating the probe 1 with the laser light with the probe 1 being separated at a desired distance from the circuit to be measured at the same measuring point are used to determine an absolute voltage at the measuring point from a change in the intensity of light measured by irradiating the probe 1 with the laser light with the probe 1 being separated only at a desired distance from the circuit to be measured at an arbitrary measuring point of the circuit X to be measured which operates at a high frequency as being used normally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated circuit test / diagnosis apparatus for measuring a voltage signal of an integrated circuit by utilizing an electro-optic effect and laser light.

[0002]

2. Description of the Related Art An electro-optic material whose birefringence is changed by an electric field is placed in an electric field generated by the operation of an integrated circuit,
When laser light is incident on this material, the polarization of the laser light changes due to the change in its birefringence. When the laser light that has undergone this polarization change is passed through a polarization detection optical system that uses a polarizer, the polarization change of the laser light can be converted into a change in the intensity of the laser light. By measuring the intensity change of the laser light (hereinafter referred to as light intensity change), the electric field coupled to the electro-optical material, that is, the voltage signal at the measurement point can be measured.

The above-described voltage signal measuring technique for integrated circuits is called electro-optical sampling. In this electro-optic sampling, the amount of coupling between the electro-optic material and the electric field varies depending on the distance between the probe and the circuit to be measured (hereinafter referred to as the distance), so that the change in the detected light intensity strongly depends on the distance.

However, there is no conventional technique relating to probe positioning for determining this separation distance, and until now, the probe was brought close to or in contact with the circuit to be measured until S / N sufficient to measure the voltage signal was obtained. I was measuring in the state.

[0005]

In the above-mentioned conventional method for measuring the voltage signal of the integrated circuit, the reproducibility of the measurement is poor due to the variation in the separation distance with respect to the repeated positioning of the probe, and the relative voltage waveforms are relatively different from each other. Although the time information such as the time delay and the rise time and fall time of the waveform was obtained, the amplitude and absolute voltage of the waveform, which are especially important for analog circuit measurement, were not measured.

The present invention solves the above-mentioned problems of the prior art, improves the reproducibility of measurement, and makes it possible to measure the absolute voltage and waveform amplitude required for waveform comparison, and a voltage signal measuring method for an integrated circuit. And a measuring device.

[0007]

In order to determine the distance between the probe and the circuit to be measured, the integrated circuit voltage signal measuring apparatus according to the present invention is arranged so that the probe and the circuit to be measured are brought close to each other by a fine movement mechanism, and the contact point is used as a reference. Is equipped with means for positioning the probe at a desired distance from each other, and means for detecting a slight contact between the probe and the circuit to be measured with high sensitivity for positioning with high accuracy. It is characterized in that it is provided with means for mitigating damage given to the measuring circuit.

In the method of measuring a voltage signal of an integrated circuit according to the present invention, first, a known low-frequency voltage signal is input to the input / output or power supply terminal of the circuit without operating the circuit to be measured, and the terminal is input. With the probe in contact with the wiring connected to the laser beam, change the light intensity measured by irradiating the laser beam on the probe and the laser beam on the probe at the same measurement point with the probe separated from the circuit under test by the desired distance. Using the change in the light intensity measured by irradiating with, measure the probe at a desired distance from the circuit under test at any measurement point of the circuit under test operating at high frequency under normal use conditions. It is characterized in that the absolute voltage at the measurement point is obtained from the change in light intensity measured by irradiating the laser beam.

The voltage signal measuring device for an integrated circuit according to the present invention is characterized in that the electro-optical material used for the probe detects an electric field in the vertical direction immediately above the wiring.

[0010]

[Function] The probe and the circuit to be measured are brought close to each other by the fine movement mechanism. Based on the contact point, they are positioned apart from each other by a desired distance. As a result, the distance between the probe and the circuit to be measured can be easily and accurately determined.

Further, by measuring the separation distance dependency of the light intensity change with a low frequency signal by utilizing the above-mentioned mechanism of bringing the probe and the circuit to be measured into contact with each other and separating them from each other, The absolute voltage can be obtained at any measurement point of the circuit under measurement operating at, and at any separation distance.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a general configuration of a voltage signal measuring device for an integrated circuit according to the present invention. The configuration of the voltage signal measuring device of this integrated circuit and the voltage signal measuring method using this device will be described below.

In FIG. 1, 1 is a probe for measuring an electric field in which an electro-optic material is fixed to the tip of a transparent material, 2
Is a probe holder, 3 is a first vertical fine movement mechanism capable of finely moving the probe holder 2 up and down with high precision, 4 is a connecting portion, and 5 is a second vertical fine movement mechanism capable of finely moving the circuit under test X with high precision.
Reference numeral 8 is a laser light source, 9 is a laser light detection device, 10 is a mirror, and 12 is a contact detection unit. The circuit to be measured X is set on the second vertical fine movement mechanism 5 and the probe holder 2 set on the first vertical fine movement mechanism 3 is arranged above the circuit. The laser light source 8 causes the laser light to enter the probe 1, Care is taken so that the reflected laser light is changed in its optical path by the mirror 10 and enters the laser light detecting device 9.

More specifically, the probe 1 is formed by fixing an electro-optic material with a transparent material and processing the tip into a needle shape for measuring an integrated circuit. The electro-optical material used for the probe 1 is for detecting an electric field in the vertical direction immediately above the wiring. For example, a crystal such as GaAs, KD ^* P, ZnTe, CdTe, or an organic optical material generated so as to have sensitivity to the vertical electric field. To use.

Epizo actuators, electromagnetic coils, stepping motors and the like are used for the first and second vertical fine movement mechanisms 3 and 5.

The connecting portion 4 reduces the effective weight of the probe 1 including the probe holder 2 and alleviates damage to the probe 1 and the circuit under test X when the probe comes into contact with the connecting portion 4. For example, a mechanism such as a balance, a spring, a magnet, or pneumatic pressure is used. To use.

The contact detector 12 detects the displacement of the probe 1 or the probe holder 2 caused by the contact between the probe 1 and the circuit under test X. For example, an image processing device, a laser displacement meter, an eddy power source detection sensor, a capacitance detection sensor. To use.

The laser light detecting device 9 converts the laser light, which has undergone polarization change in the probe 1, into a light intensity change by a polarizer and measures the light intensity change.

As the laser light source 8, a laser capable of generating a short pulse such as a YAG laser, a YLF laser, or a semiconductor laser is used, and the laser light source is selected according to the band of the voltage signal to be measured and the wavelength characteristic of the electro-optical material.

In the integrated circuit voltage signal measuring method according to the present invention, the measuring device having the above-mentioned configuration is used to determine the distance between the probe 1 and the circuit X to be measured by setting the first and second fine movement mechanisms 3, 5 therebetween. To bring the probe 1 and the circuit under test X into close contact with each other by a desired distance based on the contact point, and to detect the slight contact between the probe 1 and the circuit to be measured X with high sensitivity. Detect with.

The probe 1 and the circuit under test X can be positioned with high precision by the procedure using the contact point as a reference. ..

Further, the function of the connecting portion 4 can mitigate the damage given to the probe 1 and the circuit under test X at the time of contact of the probe.

Further, in the method of measuring the voltage signal of the integrated circuit according to the present invention, by utilizing the positioning method, first, the circuit under test is not operated and the voltage of the known low frequency is applied to the input / output terminal of the circuit or the power supply terminal. A signal is input, the probe is in contact with the wiring connected to the terminal, and the change in the light intensity measured by irradiating the probe with laser light and the probe at the same measurement point at the desired distance from the circuit under test Using the light intensity change measured by irradiating the probe with laser light in a separated state, the probe is desired from the measured circuit at any measurement point of the measured circuit operating at high frequency under normal use conditions. It is possible to obtain the absolute voltage at the measurement point from the change in the light intensity measured by irradiating the probe with laser light in the state of being separated by the distance of.

A more specific embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a voltage signal measuring device for an integrated circuit according to the first embodiment of the present invention. This device is particularly applicable when using a probe having an extremely small weight. The configuration of the voltage signal measuring device of this integrated circuit and the voltage signal measuring method using this device will be described below.

In FIG. 2, 1 is a probe for measuring an electric field in which an electro-optic material is fixed to the tip of a transparent material, 2
Is a probe holder, 3 is a first vertical fine movement mechanism capable of finely moving the probe holder 2 up and down with high precision, 5 is a second vertical fine movement mechanism capable of finely moving the circuit under test X with high precision, 6 is a camera,
Reference numeral 7 is an image processing device, 8 is a laser light source, 9 is a laser light detection device, 10 is a mirror, and 11 is a dichroic mirror. The measured circuit X is set in the second vertical fine movement mechanism, the probe holder 2 set in the first vertical movement mechanism 3 is arranged above it, and the camera 6 is arranged so that the probe 1 mounted on the probe holder 2 can be photographed. The laser light source 8 is arranged so that the laser light is incident on the probe, and the laser light reflected from the probe 1 changes its optical path by the mirror 10 and enters the laser light detection device 9.

The probe 1 is made by fixing an electro-optical material with a transparent material and has a tip processed into a needle shape for measuring an integrated circuit, and has a collar 14 formed on an upper portion thereof.

As shown in FIG. 3, the probe holder 2 is arranged so that the probe 1 can be easily moved when the tip (lower part) of the probe 1 contacts the circuit under test X and receives a force in the upward direction. It supports the probe 1. In this embodiment, the probe holder 2 is formed with a hole 2A through which the probe 1 can be loosely penetrated so that it is caught by the collar 1A.
Probe 1 is inserted in A.

The structure in which the probe 1 is placed on the probe holder 2 so that it can be easily moved by an upward force has the following advantages (1) to (3).

(1) It is possible to manufacture the probe 1 having a weight of about 0.1 g to 0.3 g. If such an extremely lightweight probe 1 is used, the probe 1 comes into contact with the circuit X to be measured. However, there is almost no damage to both.

(2) Since the probe 1 is easily displaced by a slight contact, the contact can be detected with high sensitivity.

(3) If the contact point can be detected with high sensitivity, the displacement of the probe 1 at the time of contact can be neglected because it is extremely small, and the reproducibility of measurement can be maintained for repeated probe positioning.

The camera 6 and the image processing device 7 are used to detect a contact point. That is, the contact point is obtained by observing the probe 1 with a camera and detecting a slight deviation of the observed image of the probe before and after the contact with the image processing device 7 via the dichroic mirror 11.

Next, the method of measuring the voltage signal of the integrated circuit of the present invention using the device of the first embodiment will be described with reference to FIGS. 4, 5, 6, 7 and 8.

This voltage signal measuring method utilizes the following properties of electro-optical sampling using an electro-optical material having sensitivity to a vertical electric field directly above the wiring.

(1) The change in the light intensity measured with the probe 1 in contact with the wiring is constant regardless of the shape of the wiring width, which corresponds to the measurement of the absolute voltage.

(2) The change in light intensity strongly depends on the distance between the probe 1 and the circuit under measurement X, and simply decreases as the distance increases.

(3) If the distance between the probe 1 and the circuit under test X is constant, the change in light intensity and the voltage under test are in a proportional relationship.

First, for the following reason, the change in light intensity is measured on the wiring connected to the signal input / output terminal of the circuit under test or the power supply terminal using the low frequency signal in the situation of S1 in FIG.

(1) When a low-frequency signal is applied to an input / output or power supply terminal, the amplitude does not change on the wiring connected to that terminal, so measurement may be performed at any point on the wiring. ..

(2) From the low-frequency signal used here to the high-frequency signal when the circuit is operating, since the electro-optical material having flat frequency characteristics is used, the measurement result of the low-frequency signal is converted into the high-frequency measurement result. Applicable.

(3) Since there is no heat generation for low frequency signals, there is no problem even if the probe 1 is brought into contact with the wiring. Further, if it is a low frequency signal, there is no problem of disturbance due to contact.

(4) A known voltage signal can be directly applied from the outside only at the measurement points on the wiring connected to the input / output and power supply terminals.

In the low frequency signal measurement, first, the probe 1 is brought into contact with the wiring connected to the signal input / output terminal of the circuit under test X or the power supply terminal in the following procedure.

First, the probe 1 is arranged above the wiring to be measured, the first vertical fine movement mechanism 3 is fixed, and only the circuit under test X is gradually raised by the second vertical fine movement mechanism 5.
Then, as shown in FIG. 3, the probe 1 and the circuit under test X come into contact with each other at a certain position, and the probe 1 is displaced. This slight displacement is detected by the image processing device 7 via the camera 6, and the second vertical fine movement mechanism 5 is stopped at this point.

Next, the circuit under test X is not operated, and a known low frequency signal (voltage V ₀ ) is applied to the contacted wiring from the terminal. Then, the probe 1 is irradiated with the laser light to obtain the light intensity change ΔI ₀ (state A in FIG. 5) of the laser light. Probe 1
Since an electro-optic material having sensitivity only to the vertical electric field directly above the wiring is used for, the data obtained here corresponds to the absolute voltage of the wiring.

Further, since the measurement data of the contact state does not depend on the pattern such as the wiring width, there is no terminal in the integrated circuit circuit or another pattern for contact, or there is no place to contact and measure in the circuit. The pattern Y on another chip may be measured in the situation of S3 in FIG.

Next, from the above state where the probe 1 and the circuit to be measured X are in contact with each other at the same measuring point, the circuit to be measured X is lowered by the second vertical fine movement mechanism 5, and the probe 1 is set with the contact point as a reference.
And the circuit under test X are separated by desired distances h ₁ and h _2, and the probe 1 is irradiated with the racer light to obtain the light intensity changes ΔI ₁ and ΔI _{2 of the} laser light (state B and state C in FIG. 5). ..

As shown in FIG. 6, the change in the light intensity depends on the separation distance h.
Can be approximated by a simple function, for example, a quadratic function, since increases with increasing. Therefore, in the actual measurement of the integrated circuit, if the separation distance h is changed and data is collected at some points and fitting is performed with a quadratic function as shown in FIG. 7, it is possible to know the change in the light intensity with respect to an arbitrary separation distance h. it can.

Further, as can be seen from FIG. 6, generally h
Since the change in the vicinity of = 0 becomes extremely rapid, it is difficult to estimate the value of h = 0 from the value of h ≠ 0, and even if it is estimated, the accuracy becomes poor. On the contrary, if the value at h = 0 is known, h
Since the number of data when ≠ 0 is not required so much, the measurement of h = 0 is indispensable to improve the accuracy of fitting.

Next, in the situation of S2 in FIG. 4, the circuit portion X _c of the circuit under test X operating at a high frequency in a normal use state.
The change in light intensity is measured at any of the measurement points. Here, if the light intensity change is measured while the probe 1 is in contact with the circuit operating at high frequency, there is an influence of heat generated from the circuit on the probe 1 and an influence of a disturbance (load) on the capacitive circuit. The probe 1 must be separated by a certain distance.

Therefore, first, the most appropriate separation distance hm is determined by the measurer from the contradictory conditions of sensitivity, disturbance, and thermal effect. Next, the light intensity change ΔI ₃ corresponding to the reference voltage V ₀ when the distance is hm is obtained from the distance dependency of the light intensity in FIG. 7.

Here, since the change in light intensity is proportional to the voltage to be measured if the distance is constant, the voltage V and the change in light intensity ΔI.
The relationship is obtained as a straight line shown in FIG. Finally, the absolute voltage of the circuit operating at high frequency is obtained based on FIG.

In the measurement, the probe 1 is arranged above the measurement point (contact point), the first vertical fine movement mechanism 3 is fixed, and only the circuit under test X is gradually raised by the second vertical fine movement mechanism 5. Then, as shown in FIG. 3, the probe 1 and the circuit under test X come into contact with each other at a certain position, and the probe 1 changes.

When the image processing device 7 detects the start of this displacement from the slight change in the observed image from the camera 6, the second vertical fine movement mechanism 5 is stopped at this point.

From this contact state, the circuit to be measured X is lowered by the second vertical fine movement mechanism 5 to separate the probe 1 and the circuit to be measured 4 from the contact point by a desired separation distance hm,
The probe 1 is irradiated with laser light and the change in the light intensity of the laser light ΔIm (state D in FIG. 5) is measured.

As a result, the voltage V corresponding to ΔIm can be obtained from the relationship between the voltage V and the light intensity change ΔI shown in FIG.
This is the absolute voltage at the measurement point of the circuit under test operating at high frequency.

In the above description, the separation distance is set using only the second vertical fine movement mechanism 5, but the following (1) to (3) are used.
You may do like this.

(1) First, the second vertical fine movement mechanism 5 is fixed, the probe 1 is gradually lowered by the first vertical fine movement mechanism 3, and the displacement of the probe 1 causes the probe 1 and the circuit under test X to be measured.
The first up-and-down fine movement mechanism 3 is stopped at the time when the contact with is detected. Next, the probe 1 is raised by the first vertical fine movement mechanism 3 to a desired distance, the distance between the probe 1 and the circuit under test X is determined, and the probe is positioned.

(2) First, the first vertical fine movement mechanism 3 is fixed, the circuit under test X is gradually raised by the second vertical fine movement mechanism 5, and the displacement of the probe 1 causes the probe 1 to contact the circuit under measurement X. The second up-and-down fine movement mechanism 5 is stopped at the time point when is detected. Next, the probe 1 is raised by the first vertical fine movement mechanism 3 to a desired distance, the distance between the probe 1 and the circuit under test X is determined, and the probe is positioned.

(3) First, the second vertical fine movement mechanism 5 is fixed, the probe 1 is gradually lowered by the first vertical fine movement mechanism 3, and the displacement of the probe 1 causes the probe 1 and the circuit under test X to be measured.
The first up-and-down fine movement mechanism 3 is stopped at the time when the contact with is detected. Next, the circuit to be measured X is lowered by the second vertical fine movement mechanism 5 to a desired distance, the distance between the probe 1 and the circuit to be measured X is determined, and probe positioning is performed.

FIG. 9 shows an integrated circuit voltage signal measuring device according to a second embodiment of the present invention. This device is designed to hold the probe by a mechanism that effectively reduces the weight of the probe and is particularly useful for positioning not only a light probe but also a heavy probe weighing several grams or more. Hereinafter, the configuration of the voltage signal measuring device of this integrated circuit,
A voltage signal measuring method using this device will be described.

In FIG. 9, 1 is a probe for measuring an electric field in which an electro-optic material is fixed to the tip of a transparent material, 2 '.
Is a probe holder, 3'is a first vertical fine movement mechanism capable of finely moving the balance mechanism 13 up and down with high precision, 5 is a second vertical fine movement mechanism 5 capable of finely moving the circuit under test X with high precision, 8 is a laser light source, and 9 is A laser beam detector, 10 is a mirror, 13 is a balance mechanism having F as a fulcrum, 14 is a balancer, and 15 is a displacement gauge for highly sensitively detecting a position change at point E of the balance mechanism 13. As the displacement meter 15, for example, a commercially available optical displacement meter utilizing reflection of laser light can be used.

The circuit X to be measured is set on the second vertical fine movement mechanism 5, and the probe holder 2'set on the balance mechanism 13 is arranged above it.

The probe holder 2'of the present embodiment is different from the above-mentioned first embodiment in that the probe 1 is fixed and held. Instead, the probe holder 2'is connected to the balance mechanism 13 on the side opposite to the balancer 14 with the fulcrum F interposed therebetween. The balancer 14 is connected to the balance mechanism 13 so that its position can be moved. The balance mechanism 13 includes a stopper 16 that limits the tilt toward the probe 1 side.

In this way, the balance mechanism 13 and the balancer 14 are
By holding the probe 1 using
There are advantages of (3).

(1) Since an arbitrary probe effective weight can be obtained by adjusting the position of the balancer 14, not only the lightweight probe of about 0.1 to 0.3 grams described in the first embodiment but also several grams. Even in the case of the heavy probe described above, the effective probe weight can be reduced until damage to the probe 1 and the circuit under measurement X due to contact can be ignored.

(2) Since the probe effective weight is reduced, the balance mechanism 13 can handle even a slight contact.
The probe 1 is rotationally displaced with high sensitivity around the fulcrum F of.

(3) Furthermore, if the length L ₁ from the fulcrum F to the observation point E is made longer than the length L ₂ from the fulcrum F to the tip of the probe 1, a minute amount of the probe 1 due to contact is obtained. Since the displacement can be increased to a large displacement of the observation point E, high sensitivity of contact point detection can be realized.

Next, the method of measuring the voltage signal of the integrated circuit of the present invention using the device of the second embodiment will be described with reference to FIGS. 4, 5, 6, 7 and 8.

First, in the situation of S1 in FIG. 4, the change in light intensity is measured using a low frequency signal on the wiring connected to the signal input / output terminal of the circuit under test or the power supply terminal.

In the low frequency signal measurement, first, the probe 1 is brought into contact with the wiring connected to the signal input / output terminal of the circuit under test X or the power supply terminal in the following procedure.

The probe 1 is arranged above the wiring to be measured, the first vertical fine movement mechanism 3'is fixed, and only the measured circuit 4X is gradually raised by the second vertical fine movement mechanism 5.
Then, as shown in FIG. 10, the probe 1 and the circuit under measurement X come into contact with each other at a certain position, and the balance mechanism 13 shifts from the horizontal state to the inclined state. That is, the probe 1 is displaced by the contact, and the displacement becomes the displacement of the observation point E by the balance mechanism 13. The displacement of the observation point E is detected by the highly sensitive displacement meter 15, and the second vertical fine movement mechanism 5 is stopped at that time. At this time, the circuit under test X does not operate and a known low frequency signal (voltage V ₀ ) is applied to the contacted wiring from the terminal. Then, the probe 1 is irradiated with laser light to change the light intensity of the laser light Δ
I ₀ (state A in FIG. 5) is measured.

Next, as in the first embodiment, from the above-mentioned state in which the probe 1 and the circuit under test X are in contact with each other at the same measuring point, the circuit under test X is lowered by the second vertical fine movement mechanism 5 and the contact point is reached. the separated probe 1 relative to the circuit under test X desired distance h1, h2, light intensity change [delta] I ₁ of the laser beam is irradiated with a laser beam to the probe 1, delta ₂ (state B and C in FIG. 5) To measure.

From the above measurement results, the separation distance dependency of the change in light intensity is obtained, and fitting is performed with a quadratic function as shown in FIG.

Next, in the state of S2 in FIG. 4, the circuit portion X of the circuit under test X operating at a high frequency in a normal use state.
Measure the light intensity change at any measurement point in _c .

Similar to the first embodiment, an appropriate separation distance hm is determined, and the light intensity change ΔI ₃ corresponding to the reference voltage V ₀ when the separation distance is hm is determined from the dependence of the light intensity on the separation distance in FIG.
Then, the relationship between the voltage V and the light intensity change ΔI shown in FIG. 8 is obtained.

In the measurement, the probe is arranged above the measurement point (contact point), the first vertical fine movement mechanism 3'is fixed, and only the circuit under test X is gradually raised by the second vertical fine movement mechanism 5. Then, as shown in FIG. 10, the probe 1 and the circuit under measurement X come into contact with each other at a certain position, and the balance mechanism 13 shifts from the horizontal state to the inclined state. That is, the probe 1 is displaced by the contact, and the displacement becomes the displacement of the observation point E by the balance mechanism 13.

The displacement start of the observation point E is detected by the highly sensitive displacement gauge 15, and the second vertical fine movement mechanism 5 is stopped at that time.

From this contact state, the circuit to be measured X is lowered by the second vertical fine movement mechanism 5, and the probe 1 and the circuit to be measured X are separated by the separation distance hm based on the contact point, and the laser beam is emitted to the probe 1. Irradiation changes the laser light intensity ΔI
m (state D in FIG. 5) is measured.

As a result, the voltage V corresponding to ΔIm can be obtained from the relationship between the voltage V and the light intensity change ΔI shown in FIG.

In the above description, the separation distance is determined using only the second vertical fine movement mechanism 5, but the following (1) to (3) are used.
You may do like this.

(1) First, the second vertical fine movement mechanism 5 is fixed, the probe 1 is gradually lowered by the first vertical fine movement mechanism 3 ', and the probe 1 and the circuit under test X are brought into contact with each other due to the displacement of the probe 1. At the time of detection, the first vertical fine movement mechanism 3'is stopped. Next, the probe 1 is raised by the first vertical fine movement mechanism 3'to a desired distance, the distance between the probe 1 and the circuit under test X is determined, and the probe is positioned.

(2) First, the first vertical fine movement mechanism 3'is fixed, and the circuit under test X is gradually raised by the second vertical fine movement mechanism 5, and the displacement of the probe 1 causes the probe 1 and the circuit under measurement X to move. When the contact is detected, the second vertical fine movement mechanism 5 is stopped. Next, the probe 1 is raised by the first vertical fine movement mechanism 3'to a desired distance, the distance between the probe 1 and the circuit under test X is determined, and the probe is positioned.

(3) First, the second vertical fine movement mechanism 5 is fixed, the probe 1 is gradually lowered by the first vertical fine movement mechanism 3 ', and the displacement of the probe 1 causes the probe 1 to come into contact with the circuit under test X. At the time of detection, the first vertical fine movement mechanism 3'is stopped. Next, the circuit to be measured X is lowered by the second vertical fine movement mechanism 5 to a desired distance, the distance between the probe 1 and the circuit to be measured X is determined, and probe positioning is performed.

FIG. 11, FIG. 12, FIG. 13, and FIG. 14 show another embodiment relating to the first fine vertical movement mechanism, the connecting portion, and the contact detecting portion of the voltage signal measuring device of the present invention.

In the configuration of FIG. 11, the first vertical fine movement mechanism is realized by the piezo actuator 23 arranged on the frame 21 supporting the probe holder 2. The connecting portion is realized by the repulsive force of the magnet 24 arranged between the probe holder 2 and the frame 21. Further, the contact detection unit is composed of the probe holder 2 and the frame 2.
It is realized by detecting the change of the eddy current of the eddy current displacement sensor 22 arranged between the two.

In the configuration of FIG. 12, the first vertical fine movement mechanism is realized by the piezo actuator 23 arranged on the frame 21 supporting the probe holder 2. Further, the contact portion is realized by the lift force of the air from the pneumatic mechanism 34 incident on the probe holder 2. Further, the contact detection unit is realized by detecting a change in the capacitance of the capacitance displacement sensor 32 arranged between the probe holder 2 and the frame 21.

In the configuration of FIG. 13, the first vertical fine movement mechanism is realized by the electromagnetic coil 33 arranged on the frame 21 supporting the probe holder 2. The connecting portion is realized by the leaf spring 44 supporting the probe holder 2. Further, the contact detection unit is an electric contact sensor 42 arranged between the probe holder 2 and the frame 21.
It is realized by detecting the presence or absence of electrical continuity.

In the configuration of FIG. 14, the first vertical fine movement mechanism is realized by the piezo actuator 23 arranged on the frame 21 supporting the probe holder 2. The connecting portion is realized by a spring 54 arranged between the probe holder 2 and the frame 21.
Further, the contact detection unit is realized by detecting a change in the eddy current of an eddy current displacement sensor 22 arranged between the probe holder 2 and the frame 21.

Although not mentioned in the above embodiment, since it is necessary to set an arbitrary measurement point on the circuit under test X, in addition to the first and second fine vertical movement mechanisms 3 and 5, the front, rear, left and right The moving mechanism is used to move the probe 1 or the circuit under test X back and forth and left and right to set measurement points.

Further, the lowering operation of the first vertical fine movement mechanism 3 or the raising operation of the second vertical fine movement mechanism 5 for contact, and the subsequent detection of the contact point by the image processing device 7 or the displacement meter 15 and the vertical movement at the time of detection. The fine movement mechanism 3 or 5 is stopped, the first vertical fine movement mechanism 3 is moved up to a desired interval after contact detection, or the second vertical fine movement mechanism 5 is lowered, and the voltage signal is measured after the probe is positioned. An appropriate device may be provided with a control function necessary for automatically performing.

The absolute voltage measurement in the present invention does not mean to determine a universal voltage reference, but means to perform voltage calibration.

[0095]

According to the present invention, the circuit is not disturbed,
Absolute voltage can be measured with good reproducibility at any measurement point of the integrated circuit without the influence of heat generated from the circuit on the probe. As a result, the amplitude information required by the analog circuit is obtained, and it becomes possible to compare the waveforms within the same circuit under test or the amplitudes between other circuits under test.

[Brief description of drawings]

FIG. 1 is a diagram showing a general configuration of a voltage signal measuring device of the present invention.

FIG. 2 is a diagram showing the configuration of the voltage signal measuring device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a state when the probe and the circuit under measurement are in contact with each other in the voltage signal measuring device according to the first embodiment.

FIG. 4 is a diagram showing a situation of a probe arrangement position in the voltage signal measuring method of the present invention.

FIG. 5 is a diagram showing a transition of a measurement state in the voltage signal measuring method of the present invention.

FIG. 6 is a diagram showing a relationship between a change in light intensity and a separation distance in electro-optic sampling.

FIG. 7 shows the relationship between the change in light intensity and the distance when a low frequency signal is input, which is obtained by the voltage signal measuring method of the present invention.

FIG. 8 is a diagram showing a relationship between a change in light intensity when a high-frequency signal is input and an absolute voltage at a measurement point of a circuit under measurement, which is obtained by the voltage signal measuring method of the present invention.

FIG. 9 is a diagram showing the configuration of a voltage signal measuring device according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a state when the probe and the circuit under measurement are in contact with each other in the voltage signal measuring device according to the second embodiment.

FIG. 11 is a diagram showing another configuration example of the main part of the voltage signal measuring device of the present invention.

FIG. 12 is a diagram showing another configuration example of the main part of the voltage signal measuring device of the present invention.

FIG. 13 is a diagram showing another configuration example of the main part of the voltage signal measuring device of the present invention.

FIG. 14 is a diagram showing another configuration example of the main part of the voltage signal measuring device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 probe 2 probe holder 3 first vertical fine movement mechanism 4 connection part 5 second vertical fine movement mechanism 6 camera 7 image processing device 8 laser light source 9 laser light detection device 10 mirror 11 dichroic mirror 12 contact detection unit 13 balance mechanism 14 balancer 15 Displacement Meter 16 Stopper 21 Frame 22 Eddy Current Displacement Sensor 23 Piezo Actuator 24 Magnet 32 Capacitance Displacement Sensor 33 Electromagnetic Coil 34 Pneumatic Mechanism 42 Electrical Contact Sensor 44 Leaf Spring 54 Spring X Measured Circuit

Claims (5)

[Claims] 1. A probe in which an electro-optic material whose birefringence index changes by an electric field is fixed by a transparent material is brought close to a circuit to be measured, the probe is irradiated with laser light, and an electric field generated by the operation of the circuit to be measured is used. A method of measuring a voltage signal of a circuit under measurement by changing the polarization of the laser light, converting the laser light subjected to the polarization change into a light intensity change by a polarizer, and measuring the intensity change. ) A low-frequency signal of known voltage is applied to the terminal at the measurement point on the wiring that is connected to the terminal of the circuit under test and a voltage signal can be directly supplied, and the laser light is irradiated to the probe to measure the change in light intensity. (B) The relationship between the change in light intensity measured in (a) above and the distance between the probe used in the measurement and the circuit under measurement is determined for a known voltage of the low frequency signal, and (c) above (b) ) Relationship found in On the basis of the above, the proportional relationship between the change in light intensity and the absolute voltage is obtained for a desired distance, and (d) a laser beam is placed at a desired distance using a high frequency signal at a desired measurement point in the circuit under test. Is irradiated to the probe to measure the change in the light intensity, and (e) the absolute voltage at the desired measurement point is obtained based on the proportional relationship obtained in (c) and the change in light intensity measured in (d) above. A method for measuring a voltage signal of an integrated circuit, comprising: 2. A probe having an electro-optical material whose refractive index changes by an electric field, a means for moving the probe and a circuit under measurement relatively, a laser light source for irradiating the probe with laser light, and the probe. A means for measuring a change in light intensity from a laser beam that has undergone a polarization change due to an electric field of a circuit under measurement reflected from the device; and a means for detecting a contact point between the probe and the circuit under measurement. Voltage measuring device for integrated circuit. 3. The voltage signal measuring device for an integrated circuit according to claim 2, further comprising means for mitigating damage to the probe and the circuit under test when the probe comes into contact with the circuit under test. 4. An electro-optic crystal whose refractive index changes according to the electric field strength applied to the crystal is placed in an electric field, and the electric field strength is measured from the change in the polarization state of the laser light transmitted through the crystal. When a probe, which is an electro-optic crystal processed for electric field measurement of an integrated circuit, is brought close to the measured integrated circuit to measure an electric signal waveform, (1) the probe and the measured integrated circuit are brought close to each other; ) Detecting the contact point between the probe and the integrated circuit under test, and (3) separating the probe and the integrated circuit under test by a desired amount based on the contact point, and measuring the electric field of the integrated circuit. Method for positioning probe. 5. A method of placing an electro-optic crystal in which the refractive index of the crystal changes according to the electric field strength applied to the crystal in an electric field and measuring the electric field strength from the change in the polarization state of the laser light transmitted through the crystal is used. In a probe positioning device for measuring an electric signal waveform by bringing a probe, which is an electro-optic crystal processed for electric field measurement of an integrated circuit, close to the measured integrated circuit, (1) the probe and the measured integrated circuit (2) The probe and the measured integrated circuit are separated from each other by a desired amount based on the point where the contact detection means detects the contact between the probe and the measured integrated circuit. A probe positioning device for measuring an electric field of an integrated circuit, comprising: