JPH0743393A - Voltage measuring method - Google Patents

Abstract

PURPOSE:To allow highly accurate measurement of voltage by irradiating an electrooptical crystal with a light beam in order to detect the polarized state of the crystal based on the transmitted light and detecting the electric field being imparted to a measuring electrode applied to the crystal, depending on a voltage to be measured generated from an object, based on the polarized state. CONSTITUTION:A reference electrode 12 arranged on an electrooptical crystal 9 is applied with a first predetermined voltage and the voltage is measured in a plurality of phases by means of a detection optical system 29. Subsequently, the electrode 12 is applied with a second predetermined voltage and the voltage is measured in a plurality of phases. A signal processing section 15 digitizes the measurement data before it is fed to a controller 2. The controller 2 calculates the average value of first and second measurements while at the same time dividing the difference between the first and second measurements by the difference between the first and second predetermined voltages thus calculating the detection sensitivity of voltage. The average value is then divided by the voltage detection sensitivity thus standardizing the measurements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage measuring method, and more particularly to a voltage measuring method utilizing an electro-optic effect.

LSI (Large Scale Integrated Circui)
When developing and manufacturing electric and electronic devices such as t),
In order to confirm its operation and evaluate its characteristics, it is essential to accurately measure the signals on the signal lines inside and outside the device. However, device miniaturization in recent years,
With the increase in speed, it has become difficult to obtain the required measurement accuracy with the conventional electrical measurement method.

The electro-optic effect is known as a phenomenon in which the refractive index ellipsoid of a crystal changes according to an electric field.
As a voltage measuring method utilizing this electro-optical effect, there is a method of measuring the voltage of an object to be measured by passing light through an electro-optical crystal that is in contact with or close to a terminal to be measured of a device and detecting the deflection state of the light. is there.

The response of the electro-optical effect is extremely fast,
Since the influence on the measured object such as load capacity is small,
According to this method, it is possible to accurately measure a high speed signal.

Further, in order to improve the measurement bandwidth and time resolution, electro-optical sampling (EO (ELEC
TROOPTICAL) sampling technology is used.

In the EO sampling technique, a laser pulse is used to form an optical pulse having an extremely short time width to perform sampling measurement, which enables measurement with extremely high time resolution.

In recent years, by using this EO sampling technique, voltage waveform measurement utilizing the electro-optical effect of the semiconductor element itself, and bringing a minute electro-optical crystal close to the internal wiring of the LSI, the electrical induced by the wiring voltage is used. The wiring voltage waveform is measured by sampling and detecting the change of the refractive index ellipsoid in the optical crystal with laser light.

[0008]

2. Description of the Related Art In a method of performing measurement without bringing the electro-optic crystal into contact with the symmetrical electrode to be measured, the detection sensitivity of the electro-optic crystal depends on the distance between the electro-optic crystal and the electrode. At this time, the detection sensitivity is generally not corrected.

On the other hand, a measuring electrode is attached to the electro-optic crystal and brought into contact with an input / output terminal of a symmetrical LSI to be measured, and a laser beam is deflected by an optical deflector to irradiate the measuring electrode for scanning. , LS using EO sampling technology
A method of measuring the voltage of an input / output terminal such as I has been previously proposed by the present applicant in Japanese Patent Laid-Open No. 28566/1990.

When the voltage to be measured is directly applied to the electro-optic crystal as described above, a detection signal value obtained by detecting the electro-optic effect of the electro-optic crystal by, for example, a method of measuring a terminal having a voltage waveform of known amplitude. Is measured in advance, it is possible to convert the measured voltage waveform into a unit of voltage.

Further, a transparent reference electrode is attached on the side opposite to the measuring electrode of the electro-optic crystal, and a conversion coefficient in volts is obtained from a detection signal value when a known voltage is applied to the reference electrode in advance, There is a way to use this conversion factor in subsequent measurements.

[0012]

However, according to the voltage measuring method using the conventional electro-optic effect, the electro-optic effect of the electro-optic crystal is generally extremely small, so that a highly accurate detection signal value can be stably obtained. It was difficult to get.

That is, a conversion coefficient for converting a detection signal value into a voltage value in volts is obtained by measuring a known voltage waveform in advance before measurement, and a conventional voltage using this conversion coefficient in the subsequent measurements. The measurement method has a problem that a measurement error occurs when the signal detection sensitivity of the measurement device changes due to changes in the ambient temperature and changes in the adjustment state of the optical system.

Therefore, an object of the present invention is to provide a voltage measuring method capable of performing highly accurate voltage measurement irrespective of fluctuations in the signal detection sensitivity of the measuring device.

[0015]

In order to solve the above problems, the present invention is configured as follows.

That is, according to the first aspect of the invention, the electro-optical crystal is irradiated with a light beam, the polarization state of the electro-optical crystal is detected based on transmitted light or reflected light, and the measured voltage generated by the measured object is measured. In accordance with a voltage measuring method for measuring a voltage to be measured by detecting an electric field applied to a measuring electrode arranged on the electro-optical crystal based on a polarization state, a reference electrode arranged on the electro-optical crystal. A first measurement step of applying a first predetermined voltage to a plurality of phases of the voltage to be measured and a second predetermined voltage to the reference electrode to measure a plurality of phases of the voltage to be measured. A second measurement step of measuring a value in the phase, an average value of the measurement results of the first measurement step and the measurement results of the second measurement step in the plurality of phases, and the first measurement step In the second measurement step A step of calculating the voltage detection sensitivity by dividing the difference between the constant result and the second predetermined voltage by the difference between the first predetermined voltage and the second predetermined voltage, and the measured value by dividing the average value by the voltage detection sensitivity. And a standardization process for standardizing the above.

According to the second aspect of the invention, the electro-optical crystal is irradiated with a light beam, the polarization state of the electro-optical crystal is detected based on the transmitted light or the reflected light, and the measured voltage generated by the measured object is detected. In accordance with a voltage measuring method for measuring a voltage to be measured by detecting an electric field applied to a measuring electrode arranged on the electro-optical crystal based on a polarization state, a reference electrode arranged on the electro-optical crystal. A first measurement step of applying a first predetermined voltage to the reference voltage and measuring values at a reference phase and another phase of the measured voltage, and applying a second predetermined voltage to the reference electrode to measure the measured voltage. Of the second measurement step of measuring the reference phase and the value in the other phase, and the average value of the difference between the measurement result in the other phase and the measurement result in the reference phase in the first and second measurement steps. Along with the criteria for the first measurement step The average value of the difference between the measurement result in the phase and the measurement result in the other phase and the difference between the measurement result in the reference phase and the measurement result in the other phase in the second measurement step is calculated as the second predetermined voltage and the average value. A configuration that includes a calculation step of calculating the voltage detection sensitivity by dividing by a difference with a predetermined voltage of 1 and a standardization step of normalizing the measured value by dividing the calculated average value by the voltage detection sensitivity. And

[0018]

According to the invention having the structure described in claim 1, the average value of the measurement results at the plurality of phases calculated in the calculation step and the voltage detection sensitivity calculated in the calculation step are both the first measurement step and Since it is obtained based on the measurement result in the second measurement step, the irradiation optical system, the detection optical system,
Alternatively, it is similarly affected by the temporal characteristic variation of the processing circuit system. Therefore, the measured value obtained by dividing them in the normalization process acts so that the influence of these characteristic fluctuations is removed.

According to the invention of the second aspect, the average value of the difference between the measurement result in the other phase calculated in the calculation step and the measurement result in the reference phase and the voltage detection calculated in the calculation step. Since both sensitivities are obtained on the basis of the measurement results in the first measurement step and the second measurement step, the influence of the temporal characteristic variation of the irradiation optical system, the detection optical system, or the processing circuit system is the same. is recieving. Therefore, the measured value obtained by dividing them in the normalization process acts as a relative voltage value in another phase based on the voltage value in the reference phase from which the influence of these characteristic fluctuations is removed. To do.

[0020]

1 is a flow chart of a first embodiment of the present invention, FIG. 2 is a block diagram showing a system configuration for carrying out the present invention, and FIG. 3 is a diagram showing a measurement principle of the present invention.
First, the system configuration of FIG. 2 will be described.

In FIG. 2, reference numeral 2 denotes a control device which includes a CPU (central processing unit; central processing unit), controls the operation of the entire system, and 3 denotes an LSI to be measured.

The LSI 3 has a plurality of input / output terminals 4 inserted into a socket 6 arranged on a test board 5,
A predetermined operation is performed by supplying a drive signal and power of a predetermined timing supplied from the I drive device 8 according to the type, test item, and the like.

Further, on the test board 5, the EO crystal contact portion 11 is in contact with a plurality of measuring light reflecting electrodes 10 arranged on the right side surface of the EO (ELECTRO OPTICAL) crystal 9 which is an electro-optical crystal in the figure. The light reflection electrodes 10 are in contact with and electrically connected to the input / output terminals 4 of the LSI 3. Even if they are not in contact with each other, the potential applied to the light reflection electrode 10 from each input / output terminal 4 can be detected according to the measured voltage generated by the LSI 3.

A transparent reference electrode 12 is provided on the left side surface of the EO crystal 9 in the figure. A predetermined voltage is applied to the reference electrode 12 from the voltage applying device 1. And EO
In the crystal 9, the irradiation optical system 25 is driven by the driver 13 based on the timing signal generated by delaying the timing signal from the LSI driving device 8 by the timing generation unit 7 for a predetermined time.
The laser light L generated by being driven by the laser is emitted through the reference electrode 12.

The irradiation optical system 25 and the detection optical system 29 constitute an optical system. The irradiation optical system 25 includes a semiconductor laser 21, a collimator lens 22, a beam splitter 23, and a scanning unit 2 such as a galvano scanner as shown in the figure.
It consists of four.

The detection optical system 29 also separates the reflected light L'of the laser light from the EO crystal 9 via the scanning section 24 and the beam splitter 23 into a horizontal polarization and a vertical polarization, Photodetectors 27 and 28 that output photodetection signals Dh and Dv according to the intensities of the horizontal polarization and the vertical polarization.
It consists of

The EO crystal 9 exhibits a well-known electro-optical effect in which the refractive index ellipsoid changes according to the voltage of the input / output terminal 4 of the LSI 3 applied to the light reflecting electrode 10 and the voltage of the reference electrode 12.

The laser light L is generated from the irradiation optical system 25 on the basis of the timing signal from the timing generator 7 according to the drive timing of the LSI 3 as described above. Therefore, the EO to which the measured terminal of the semiconductor device 3 is connected
When the predetermined light reflection electrode 10 of the crystal 9 is repeatedly irradiated with the laser light L at a pulsed timing corresponding to the period of the signal under measurement, the polarization state of the reflected light L ′ of the laser light L depends on the voltage under measurement. Change. Then, the photodetectors 27 and 28 output the photodetection signals Dh and Dv corresponding to the polarization state to the differential amplifier 14.

The signal processing section 15 is provided with the photodetection signals Dh and D of the photodetectors 27 and 28 sent from the differential amplifier 14.
A / D conversion is performed on the signal of the difference of v, and signal processing such as addition processing is performed to obtain digital data D corresponding to the voltage (or electric field) applied to the EO crystal 9, and the control device 2
Supply to.

The control device 2 measures the signal voltage at each input / output terminal 4 of the LSI 3 based on the digital data D, and measures the characteristics such as the propagation delay time of the LSI 3, for example.

Next, a first embodiment of the voltage measuring method according to the present invention will be described with reference to FIGS.

In FIG. 1, step S11 (hereinafter, step S
Is denoted by S), first the control variable j is initialized to 1
far. With this control variable j, the first measurement step S12 to S13 and the second measurement step S14 to
The number of times S15 is repeated is controlled.

At S12, the DC voltage V shown in FIG.
1 is applied to the reference electrode by the voltage application device.

Next, in step S13, the values of the measured voltage wl (ti) shown in FIG. 3 at a plurality of phases ti (i = 1 to I) are measured, respectively, and wl (t
i, j).

However,

[0036]

[Equation 1]

It is

Subsequently, in S14 to S15, similarly, the DC voltage Vh shown in FIG. 3 is applied to the reference electrode by the voltage applying device (S14), and the measured voltage wh shown in FIG.
The values of (ti) at a plurality of phases ti are measured, and these are set as wh (ti, j).

However,

[0040]

[Equation 2]

It is

In subsequent S16, it is determined whether the control variable j has reached a predetermined number of times of repetition J. Control variable j
Does not reach J (No), 1 in j in S17
Is incremented and then the process returns to S12, where S12
-The measurement of S15 is repeatedly performed.

At this time, the number of repetitions J may be 1.
When it is determined in S16 that the control variable j has reached J (Yes), the normalizing step of S19 is executed subsequent to the calculating step of S18. That is, in S18, To calculate. The value of this w (ti) is the first measurement step (S12, S13) at a plurality of phases ti of the measured voltage.
3 is an average value of the measurement result in step S1 and the measurement result in the second measurement step (S14, S15), and is indicated by a broken line in FIG.

[0044]

[Equation 3]

It is represented by

The value of w (ti) is affected by the temporal characteristic fluctuation of the irradiation optical system, the detection optical system, or the processing circuit system during the measurement in S13 and S15. Also, S
At 19, To calculate. The value of s is the amount of change [wl] in the detection signal value due to the change in the voltage applied from the voltage applying device to the reference electrode.
(ti, j) -wh (ti, j)] is the difference in applied voltage (Vh
-Vl) divided by the product of the number of measured data J × I.

That is, s represents the detection sensitivity when a unit voltage is applied to the reference electrode, and is represented by wl (ti) -wh (ti) shown by the broken line in FIG.

The value of s is affected by the temporal characteristic variation of the irradiation optical system, the detection optical system, or the processing circuit system during the measurement in S13 and S15, simultaneously with the value of w (ti).

Therefore, in S19 following S18, in order to remove the influence of these characteristic variations, w (t
The measurement result normalized by dividing the value of i) by the value of s

[0050]

[Equation 4]

Find

According to the present embodiment, from the above measurement results, the influence of the temporal characteristic fluctuation of the irradiation optical system, the detection optical system, or the processing circuit system during the measurement is removed, and the accurate voltage The measurement can be performed.

Next, a second embodiment of the voltage measuring method according to the present invention will be described with reference to the flowchart of FIG.

In step S41 in FIG. 4, the control variable j is first initialized to 1 and then, in step S42, the DC voltage Vl is applied to the reference electrode by the voltage application device and the control variable k is initialized to 1. With this control variable k, S43 to S44, which are the first measurement process,
And the number of repetitions of S48 to S49 which is the second measurement step is controlled.

In S43, the value of the measured voltage at the reference phase t0 is measured, and the measurement result is wl (t0, j,
k).

Next, in S44, the value of the measured voltage at another phase t1 which is different from the reference phase t0 by a predetermined phase is measured, and the measurement result is set to wl (t1, j, k).

Subsequently, in S45, it is determined whether the control variable k has reached a predetermined number of repetitions K. Control variable k
If K has not reached K (No), 1 is added to k in S46
Is incremented and then the process returns to S43, where S43
And S44 are repeatedly measured.

If it is determined in S45 that the control variable k has reached K (Yes), then in S47, a DC voltage Vk different from the DC voltage Vl is applied to the reference electrode by the voltage applying device and the control variable k is applied. Is initialized again and set to 1.

After initializing k, in S48, the value of the measured voltage at the reference phase t0 is measured, and the measurement result is set as wh (t0, j, k).

Next, in S49, the value of the voltage to be measured at another phase t1 different from the reference phase t0 by a predetermined phase is measured, and the measurement result is set to wh (t1, j, k).

In the subsequent step S50, it is determined whether the control variable k has reached a predetermined number of repetitions K. Control variable k
If K has not reached K (No), 1 in k in S51
Is incremented and then the process returns to S48, where S43
And the measurement of S49 is repeatedly executed.

When it is determined in S50 that the control variable k has reached K (Yes), it is then determined in S52 whether the control variable j has reached the predetermined number of repetitions J. If the control variable j has not reached J (No), S53
In j, 1 is incremented to j, the process returns to S42, and the processes of S42 to S51 are repeatedly executed.

At this time, the number of repetitions J may be 1.
When it is determined in S52 that the control variable j has reached J (Yes), the normalizing step of S55 is executed subsequent to the calculating step of S54. That is, in S54, To calculate. The value of this Δw (t1, t0) is the phase t1.
The value obtained by subtracting the measurement value at the reference phase t0 from the measurement value at is the average value of all the measurements at S42 to S53.

The values of Δw (t1, t0) are S43 and S
44, S48, and S49 are affected by the temporal characteristic variation of the irradiation optical system, the detection optical system, or the processing circuit system during the measurement. Also, in S55, To calculate. The value of s is vl at the reference phase t0.
The average value of the measured value when vh is applied is subtracted from the measured value when vh is applied, and the average value of the measured value when vh is applied is subtracted from the measured value when vl is applied at phase t1 It is divided by the product of the voltage difference (Vh-Vl) and the number of measured data J × K.

The value of s is Δw, which is the influence of the temporal characteristic fluctuation of the irradiation optical system, the detection optical system, or the processing circuit system during the measurement in S43, S44, S48, and S49.
It is received at the same time as the value of (t1, t0).

Therefore, in S55 following S54, in order to remove the influence of these characteristic variations, Δw
Normalized measurement result by dividing the value of (t1, t0) by the value of s

[0067]

[Equation 5]

Find

According to the present embodiment, from the above measurement result, the influence of the temporal characteristic fluctuation of the irradiation optical system, the detection optical system, or the processing circuit system during the measurement is removed, and at the reference phase t0. An accurate relative voltage measurement can be performed with respect to the value.

In each of the above embodiments, the rate of change of the measured amount can be obtained with sufficient accuracy by making the value of the difference in applied voltage (Vh-Vl) sufficiently large. As a result, the deterioration of the voltage resolution due to the standardization of the measurement amount with the voltage detection sensitivity can be ignored, and the detection sensitivity for the reference electrode is obtained in parallel with the measurement, so that the measurement time does not increase.

In each of the above embodiments, an example in which a direct current voltage is applied to the reference electrode for measurement has been described. However, if it is desired to consider the frequency dependence of the electro-optic effect exhibited by the electro-optic crystal, the reference electrode may be used. It is conceivable to change the voltage applied to the reference electrode by applying a voltage waveform such as a rectangular wave and changing the voltage waveform or shifting the phase thereof.

As described above, by changing the voltage value applied to the reference electrode at a certain phase by shifting the phase, the detection sensitivity to the reference electrode can be obtained at a high frequency, and the frequency dependence of the electro-optic coefficient can be obtained. Can be offset. Also, the frequency dependence of the electro-optic coefficient can be canceled by changing the voltage waveform applied to the reference electrode.

Further, in principle, when the actual voltage value in volts of the measured object cannot be obtained by the above method, the measured object whose voltage value is known beforehand is measured by the above method. According to the above, the correction coefficient for obtaining the voltage value in volts from the above standardized measurement value is measured,
In the subsequent measurement, the voltage can be measured by correcting using this correction coefficient and removing each fluctuation factor.

[0074]

As described above, according to the first aspect of the invention, the average value of the measurement results in the plurality of phases calculated in the calculation step and the voltage detection sensitivity calculated in the calculation step are both the first measurement values. Since it is obtained based on the measurement results of the process and the second measurement process, it is similarly affected by the temporal characteristic variation of the irradiation optical system, the detection optical system, or the processing circuit system. Therefore, the measured value obtained by dividing them in the normalization process is taken as the voltage value from which the influence of these characteristic fluctuations has been removed, and the voltage can be accurately measured regardless of the temporal characteristic fluctuations of the equipment. There is.

According to the second aspect of the invention, the average value of the difference between the measurement result in the other phase calculated in the calculation step and the measurement result in the reference phase and the voltage detection sensitivity calculated in the calculation step are: Since both are obtained based on the measurement results in the first measurement step and the second measurement step, they are similarly affected by the temporal characteristic fluctuation of the irradiation optical system, the detection optical system, or the processing circuit system. . Therefore, the measured value obtained by dividing them in the normalization process is the relative voltage value in other phases based on the voltage value in the reference phase from which the influence of these characteristic fluctuations has been removed, It has the feature that the relative voltage can be measured accurately regardless of characteristic fluctuations.

[Brief description of drawings]

FIG. 1 is a flowchart of a first embodiment of the present invention.

FIG. 2 is a block diagram showing a system configuration for implementing the present invention.

FIG. 3 is a diagram showing a measurement principle of the present invention.

FIG. 4 is a flow chart of a second embodiment of the present invention.

[Explanation of symbols]

 2 control device 7 timing generation part 15 signal processing part 25 irradiation optical system 29 detection optical system S11-S19, S41-S55 step

Claims (2)

[Claims] 1. An electro-optic crystal is irradiated with a light beam to detect the polarization state of the electro-optic crystal based on transmitted light or reflected light, and the electro-optic crystal is detected according to a voltage to be measured generated by an object to be measured. In a voltage measuring method for measuring the voltage to be measured by detecting an electric field applied to the arranged measuring electrode based on the polarization state, a first electrode is provided on a reference electrode arranged on the electro-optic crystal. A first measuring step (S12, S13) of measuring the values of the voltage to be measured at a plurality of phases by applying a predetermined voltage to the reference electrode, and applying a second predetermined voltage to the reference electrode. A second measurement step (S14, S15) for measuring values of the measurement voltage in the plurality of phases, and a first measurement step (S12, S1) in the plurality of phases.
3) measurement result and the second measurement step (S14, S1)
The average value with the measurement result in 5) is calculated, and the measurement result in the first measurement step (S12, S13) and the second measurement result are calculated.
A calculation step (S18) of calculating the voltage detection sensitivity by dividing the difference between the measurement result in the measurement step (S14, S15) and the difference between the first predetermined voltage and the second predetermined voltage.
And a standardization step (S19) of normalizing the measured value by dividing the average value by the voltage detection sensitivity. 2. An electro-optical crystal is irradiated with a light beam to detect the polarization state of the electro-optical crystal based on transmitted light or reflected light, and the electro-optical crystal is detected according to the voltage to be measured generated by the object to be measured. In a voltage measuring method for measuring the voltage to be measured by detecting an electric field applied to the arranged measuring electrode based on the polarization state, a first electrode is provided on a reference electrode arranged on the electro-optic crystal. The first measurement step (S42, S43,
S44), and a second measurement step (S47, S48, S49) of applying a second predetermined voltage to the reference electrode to measure the value of the measured voltage at the reference phase and the other phase. , The first and second measurement steps (S42, S43, S44,
In S47, S48, S49,), the average value of the difference between the measurement result in the other phase and the measurement result in the reference phase is calculated, and the first measurement step (S42, S4) is performed.
3, S44,) the difference between the measurement result at the reference phase and the measurement result at the other phase, and the measurement result at the reference phase at the second measurement step (S47, S48, S49) and the other Calculation step of calculating the voltage detection sensitivity by dividing the average value of the difference with the measurement result in the phase of 1 by the difference between the second predetermined voltage and the first predetermined voltage (S54).
And a standardization step (S55) of normalizing the measured value by dividing the calculated average value by the voltage detection sensitivity.