JPH05172910A - Automatic electrode voltage adjusting device for controlling secondary electron of electron beam device - Google Patents

Abstract

PURPOSE:To measure potentials at the surface of a sample through simple operation with high measured-value reproducibility under the same measuring condition even when the potentials are measured at a plurality of measurement stations. CONSTITUTION:This device is provided with a signal processing section 9 and control circuit 10 both of which measure the deviation between energy analysis curves of two secondary electrons measured against two potentials, a high and low potentials, at a reference potential part on the surface of a sample from the shapes of the curves and set the voltage values of a secondary electron controlling electrode reflector 3, collector 6a, and buffer grid 4b based on the measured deviation so that the shapes of the energy analysis curves can become constant. The section 9 finds the energy analysis curves from the secondary electrons which are generated from the reference potential part of the sample on a sample stage 5 and caught by means of a detector 6, measures a voltage amplitude error, coefficient of convergence, and gradient difference from the shapes of the curves as deviations, calculates voltage changing data so as to minimize the measured values, with the calculated data being supplied to the control circuit 10. The circuit adjusts the voltage applied across electrodes for controlling secondary electron in accordance with the voltage changing data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has no fear of destruction.
The present invention relates to an electron beam device such as an electron beam tester that measures a voltage of a sample with high spatial resolution and performs a functional test of a large-scale integrated circuit (hereinafter referred to as an LSI) and a failure analysis, and particularly a reflector electrode that controls a trajectory of secondary electrons. The present invention relates to a secondary electron control electrode voltage automatic adjustment device for an electron beam device that automatically adjusts the voltage of a secondary electron control electrode such as a buffer electrode.

[0002]

2. Description of the Related Art As a conventional LSI function test and failure analysis method, for example, a method of determining whether the LSI is good or bad depending on whether output data with respect to input data is normal, or a thin metal needle while observing with a microscope is used. There is a mechanical stylus method for measuring the electric potential and voltage waveform by making contact with and connecting it to an oscilloscope.

In the method based on input / output data, defective portions are limited to some extent by the combination of data. But,
This method is not an effective means because the degree of integration increases and the number of gates and the number of input / output pins increases and the number of defective points increases. On the other hand, in the mechanical stylus method, LS
Risk of destroying I, limit of miniaturization of measurement points, deterioration of measurement accuracy due to contact resistance and capacitance, measurement method is complicated and time-consuming, and measurement of many points is almost impossible, etc. Has the disadvantages of.

In place of the mechanical stylus method, a non-mechanical, high-speed LSI diagnosis is required, and the laser beam induced current method,
Although non-mechanical diagnostic methods such as ultrasonic scanning have been proposed,
One of them is electron beam (EB).
am) There is a device. In this method, the surface of the LSI is irradiated with an electron beam, and the potential information on the surface is acquired by secondary electrons generated from a region of less than 10 nm below the surface of the sample.

The main body of the electron beam apparatus is a scanning electron microscope (SEM).
FIG. 5 shows an overall configuration diagram of the electron beam device.

The primary electrons emitted from the electron gun 1 are converged into a beam by the condenser lens 2 and once focused.
When the primary electrons pass through the reflector 3, they are deflected by X and Y deflection coils (not shown), and then are analyzed by the analysis grid 4a,
The sample is further converged by the objective lens 4 including the buffer grid 4b and the extraction grid 4c, and is irradiated onto a predetermined position of the sample mounted on the sample stage 5.

When the primary electron beam scans the sample vertically and horizontally by the X and Y deflection coils, secondary electrons generated from the surface of the sample in response to the primary electron beam have a collector 6a. 6 (for example, Photomul etc.) captures an electrical signal. This electric signal is supplied to a CRT display through an amplifier (not shown), and a SEM image is obtained where the surface of the sample has a high potential and where the potential is low is bright.

This potential contrast is mainly due to LSI
The secondary electron passing through this electric field is further determined by the shape and potential of the sample, the objective lens 4, the detector 6 and the like. Affected by distribution. Therefore, the relationship of the secondary electron signal corresponding to the potential of the electron beam irradiation point differs depending on the electron beam device.

Generally, the signal change of the secondary electrons does not show a linear relationship with the potential change at the measuring point, but it can be corrected because there is a one-to-one correspondence. Further, the secondary electron signal is affected by the potential change of the adjacent wiring (local electric field effect). Therefore, energy quantification methods are being studied to quantify the potential measurements.

This method utilizes the fact that, as shown in FIG. 6, if the potential at the irradiation point changes, the energy distribution curve of secondary electrons shifts accordingly. As shown in the figure, the sample potential Vs is, for example, from 0 volt to minus V
At 1 volt, the energy distribution curve of secondary electrons becomes V1.
Shift only electron volts (arrow in Figure 6).

Therefore, when the applied voltage V _R of the analysis grid 4a (hereinafter referred to as an analysis voltage) is V _R1 when the potential of the sample is V ₁ , the energy having a certain value or more is 2
Since only following the electrons reach the detector 6 through the analysis grid 4a, with respect to the analysis voltage V _R1 as shown in FIG 2
An energy analysis curve obtained by integrating the energy distribution of secondary electrons is obtained. The same energy analysis curve is obtained with respect to the analysis voltage V _R2, the shift with respect to the analysis voltage V _R of energy analysis curve (Figure 7 arrow) measuring the change in the surface potential of the sample 5.

The shape of the energy analysis curve changes significantly depending on the voltages applied to the secondary electron control electrodes of the reflector 3, the collector 6a and the bufferer grid 4b. For example, when the voltage of the reflector 3 is increased more negatively than a predetermined threshold value, the trajectory of the secondary electrons changes, and the secondary electrons are no longer supplied to the detector 6. Alternatively, when the voltage of the buffer grid 4b is changed, the condition that the secondary electrons are vertically incident on the detector 6 is changed.

In order to accurately measure the potential of the surface of the sample, each applied voltage of the secondary electron control electrode is adjusted so that the energy analysis curves corresponding to the surface potential have the same shape as much as possible. There is a need. Since these voltages are manually adjusted, the reproducibility of the potential measurement value is poor, and when there are a plurality of measurement points, it is difficult to make the measurement conditions before and after the adjustment the same.

[0014]

As described above, in the conventional secondary electron controlling electrode voltage automatic adjusting device of the electron beam apparatus, the voltage of the secondary electron controlling electrode is manually adjusted, and the operation thereof is performed. However, there is a problem in that the reproducibility of the measured value of the surface potential of the sample is poor, and it is difficult to make the same measurement conditions when there are multiple measurement points, and an accurate measured value cannot be obtained. It was

The present invention has been made in view of such circumstances, and its problem is that the surface potential of a sample can be measured by a simple operation, the reproducibility of the measured value is good, and a plurality of measuring points are provided. It is an object of the present invention to provide a secondary electron control electrode voltage automatic adjustment device for an electron beam device that can make the measurement conditions the same in any case.

[0016]

In order to solve the above-mentioned problems, the invention according to claim 1 is a detector 6 for detecting secondary electrons generated when a sample is irradiated with an electron beam, and the detector 6. Secondary electron control electrodes 3 and 6 for guiding the secondary electrons
An electrode voltage automatic adjusting device for secondary electron control of an electron beam device comprising a and 4b, wherein a portion serving as a reference of potential is provided on the surface of the sample, and measurement is performed at two high and low potentials at the portion. A plurality of deviation amounts are measured from the shapes of the two secondary electron energy analysis curves, and the voltage values of the secondary electron control electrodes 3, 6a and 4b are determined based on the deviation amounts. It is configured by including signal processing means 9 and 10 for setting the shape to be a constant shape.

According to a second aspect of the present invention, in the first aspect of the present invention, as the plurality of deviation amounts, first, a difference between voltage values of the two energy analysis curves at a predetermined slice level and a preset value are set. The amount obtained as a difference between these two reference voltage values, secondly, the reciprocal value of the slope of each tangent line at the intersection of the slice level and the two energy analysis curves, and thirdly, The value of the difference between the slopes of the two tangents is used.

According to a third aspect of the present invention, in the first aspect of the present invention, a signal line for a clock signal of an integrated circuit or a pad thereof is used as a portion that serves as a reference for the voltage. According to a fourth aspect of the present invention, in the first aspect of the present invention, a voltage source line of the integrated circuit or its pad and a ground line or its pad are used as the reference portion of the voltage.

[0019]

According to the first aspect of the invention, the primary electrons emitted from the electron gun 1 are converged into a beam shape by the condenser lens 2 and the objective lens 4 and are applied to a portion on the surface of the sample which serves as a reference for the potential. To be done. The secondary electrons generated from the sample in response to the electron beam have their trajectories adjusted by the secondary electron control electrodes 3, 6a, 4b, are captured by the detector 6, and are supplied to the signal processing means 9, 10. .. The signal processing means 9 and 10 measure two energy distribution curves of secondary electrons with respect to two high and low potentials, extract a plurality of deviation amounts from their shapes, and according to the deviation amounts, the energy distribution. The voltage applied to the secondary electron control electrodes 3, 6a, 4b is adjusted so that the curve has a constant shape.

According to a second aspect of the present invention, the signal processing means 9 and 10 are, based on the secondary electron signal supplied from the detector 6, as the plurality of deviation amounts, firstly, at the predetermined slice level. An amount obtained as a difference between the voltage values of the two energy analysis curves and the difference between two preset reference voltage values, and secondly, the intersection of the slice level and the two energy analysis curves. And the value of the difference between the inclinations of the two tangents are calculated.

According to the third aspect of the invention, the high-level and low-level voltage values applied to the signal line of the clock signal of the integrated circuit or the pads thereof are set to the reference voltage values of high and low potentials on the sample surface, respectively.

According to the fourth aspect of the invention, the high level voltage value applied to the voltage source line of the integrated circuit or its pad is applied to the ground line or its pad as the high reference voltage value of the sample surface potential. The low level voltage value is set to the reference voltage value of the low potential of the sample surface potential.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an overall configuration diagram of an electrode voltage automatic adjustment device for secondary electron control of an electron beam device according to an embodiment of the present invention.

Below the electron gun 1 which emits primary electrons, 1
A condenser lens 2 having a two-stage structure for converging secondary electrons in a beam shape is arranged, and a reflector 3 is sequentially arranged below the condenser lens 2.
The objective lens 4 including the analysis grid 4a, the buffer grid 4b, and the extraction grid 4c is arranged. Between the reflector 3 and the objective lens 4, X and Y deflection coils (not shown) are provided.

A sample stage 5 is arranged below the objective lens, and a sample such as an LSI is placed on the sample stage 5. 2 emitted from the sample in response to primary electrons
A detector 6 (for example, Photomul etc.) having a collector 6 a that traps secondary electrons is arranged between the reflector 3 and the objective lens 4. The detector 6 is connected to the signal processing unit 9 via the amplifier 7 and the analog-digital converter ADC8.

On the other hand, the signal processing unit 9 is a cathode ray tube CRT 17
And the control circuit 10, which is connected to the digital-analog converter DA.
Via the C11 and the amplifier 12, to the reflector 3, via the digital-analog converter DAC13 and the amplifier 14, to the collector 6a, and via the digital-analog converter DAC15 and the amplifier 16, to the buffer grid 4b of the objective lens 4, respectively. Connected.

The reflector 3, the collector 6a, and the buffer grid 4b constitute a secondary electron control electrode for adjusting the trajectory of secondary electrons, and the signal processing section 9 is used.
Is composed of a CPU, a RAM, a ROM, and the like, stores a voltage setting processing program for a secondary electron control electrode, which will be described later, and stores the secondary electron energy based on the secondary electron signal supplied from the detector 6. An analysis curve and three deviation amounts described later are calculated from this curve. Further, the signal processing unit 9 calculates data relating to the voltages applied to the three secondary electron control electrodes from these deviation amounts, and the control circuit 1
0 supplies the voltage according to this data to each secondary electron control electrode.

Here, how to obtain the deviation amount will be described with reference to FIGS. First, the sample LS
Select a voltage reference point on the I-mold. In this embodiment, since the wiring width is sufficiently wide and is not affected by the potential of the adjacent wiring, a portion where the voltage has a constant value, for example, a pad to which a clock signal is supplied as shown in FIG. 3 is selected. Then, the energy analysis curves E ₁ and E ₂ at the low level V1 and the high level V2 of the voltage value applied to this pad are obtained by changing the voltage V _R of the analysis grid 4a (see FIG. 2).
), The low level V1 and the high level V2 are set to high and low potential reference values, respectively.

First, the voltage amplitude error A will be described.
As shown in FIG. 2, the preset slice level and the previous
Note Two energy analysis curves E₁, E₂Voltage at each intersection with
Value V _R1, V_R2Difference ΔV_R(Shift amount) and the reference voltage
The difference ΔV between the values V1 and V2 is calculated. The voltage amplitude error A is
ΔV_RIs the difference between ΔV and ΔV. The smaller this value, the better.
Yes.

Secondly, the convergence coefficient B will be described. The convergence coefficient B is the reciprocal value of the slope of the tangent line at each intersection of the slice level and the analysis curve E ₁ or E ₂ . FIG. 2 shows the convergence coefficient B of the energy analysis curve E ₁ when the pad of the clock signal is at the low level. Generally, the intersection is obtained by the binary search method, but it is known that the larger the slope of the energy analysis curve E ₁ or E ₂ , the faster the convergence and the shorter the measurement. Therefore, the smaller the value of the convergence coefficient B, the more preferable.

Thirdly, the gradient difference C is calculated. The gradient difference C is the difference in the gradient of the tangent line at the intersection of the slice level and the energy analysis curves E ₁ and E ₂ when the voltage applied to the pad of the clock signal is low level and high level. If this value is large, the value of the voltage amplitude will not be constant due to the level of the slice level, so the smaller this value is, the more preferable.

Next, the above three deviation amounts A, B and C are 2
It is considered to be a function of the respective voltages Vb, Vc, Vrf of the secondary electron control electrode, that is, the buffer grid 4b, the collector 6a and the reflector 3, and the principle of the method for obtaining the minimum value of these voltages by the Newton-Raphson method is described. Will be briefly described.

For example, if a quantity F is a function of X, then
Letting the initial value of X be X _0, and Taylor expansion of F with respect to X ₀ , and ignoring the third and subsequent terms,

[0034]

[Equation 1] Then, if F (X ₀ + Δx) = 0, then

[0035]

[Equation 2] Becomes Next, using X ₀ + Δx as the initial value X ₁ ,
Find x. Thereafter, this is sequentially repeated to obtain F (X ₀ + Δ
X is obtained such that x) = 0.

In the case of the present embodiment, the amount F corresponds to the deviation amounts A, B, C, and these deviation amounts A, B, C are functions of the voltages Vb, Vc, Vrf. A, B,
To obtain the voltages Vrf, Vc, and Vb that minimize C,
The following formula

[0037]

[Equation 3] The inverse matrix of the matrix M is applied to both sides of the above to obtain minute voltage changes ΔVb, ΔVc, and ΔVrf of the secondary electron control electrode. Here, nine variation amounts of deviation amounts A, B, and C when each element of the matrix M, that is, each electrode voltage is minutely changed are experimentally obtained.

Then, the minute voltage changes ΔVb, ΔV
The optimum voltage value can be obtained by repeating the process of adding c and ΔVrf to Vb, Vc, and Vrf, respectively.

Next, the operation of this embodiment will be described with reference to FIGS. The primary electrons emitted from the electron gun 1 are converged into a beam by the condenser lens 2 and once focused, and then pass through the reflector 3. Then, it is deflected by an X, Y deflection coil (not shown), further converged by the objective lens 4, and irradiated onto a predetermined position of the sample mounted on the sample stage 5.

After that, the electron beam scans the sample vertically and horizontally by the X and Y deflection coils, and secondary electrons generated from the surface of the sample by the electron beam are collected by the collector 6a.
Is detected by the detector 6 (for example, Photomul etc.) having an electric signal. This electric signal is supplied to the signal processing unit 9 via the amplifier 7 and the analog-digital converter ADC8.

The signal processing unit 9 calculates the deviation amount related to the energy analysis curve of the secondary electrons, that is, the voltage amplitude error A, the convergence coefficient B and the gradient difference C based on the signal supplied from the detector 6, Each voltage change data of the secondary electron control electrode is calculated and supplied to the control circuit 10 so that these deviation amounts are minimized. The control circuit 10 supplies the voltage change amount corresponding to the voltage change data to the secondary electron control electrodes, respectively.

That is, the voltage change amount ΔVrf of the reflector 3 corresponding to the voltage change data is converted into an analog signal by the digital-analog converter DAC 11, amplified by the amplifier 12, and added to the voltage value Vrf of the reflector 3 to collect the voltage. voltage change amount ΔVc of 6a is added to the voltage value V _c of the collector 6a via the digital-to-analog converters DAC13 and amplifier 14 as well, and the voltage change amount ΔVb buffer grid 4b is a digital-to-analog converters DAC15 and the amplifier 16 It is applied to the voltage value _Vb of the buffer grid 4b via the.

Then, after automatically correcting the focus and electron beam position, the voltage change data is calculated again from the deviation amount based on the voltage of the secondary electron control electrode corrected as described above. Each voltage of the secondary electron control electrode is changed according to the changed voltage data. Thereafter, the voltage change data is calculated and the voltage of the secondary electron control electrode is changed until the deviation amount becomes a predetermined threshold value. Then, when the deviation amount becomes equal to or less than the predetermined threshold value, the calibration process of the electron beam apparatus is ended.

Next, referring to the flow chart relating to the voltage processing program of the secondary electron control electrode shown in FIG.
The calibration process of the electron beam device will be described in detail. As shown in FIG. 3, after selecting the high level V ₂ and the low level V ₁ of the applied voltage at the pad of the clock signal as the reference of the high and low potentials of the sample surface, the voltage Vb of the buffer grid 4b, the voltage Vc of the collector 6a, and An initial voltage value of the voltage Vrf of the reflector 3 is set (step S1), an energy analysis curve of secondary electrons is calculated, and a deviation amount from the energy analysis curve, that is, a voltage amplitude error A, a convergence coefficient B and a gradient difference C. The value of is calculated (step S2).

Next, it is determined whether these deviation amounts A, B, C are below a predetermined threshold value (step S3). If this answer is negative, that is, No, each element of the matrix M in the above-mentioned formula (3) is measured (step S4), then the inverse matrix of the matrix M is calculated, and each voltage is applied across both sides of the formula (3). The voltage changes ΔVb, ΔVc, and ΔVrf are calculated (step S5).

Then, these voltage changes ΔVb, ΔV
c and ΔVrf are initial voltage values Vb, Vc and Vr, respectively.
After being added to f to update the voltage value (step S6), automatic correction of the focus, electron beam irradiation position, etc. is executed, and the process returns to step S2.

Again, the voltage amplitude error A, the convergence coefficient B, and the gradient difference C are calculated (step S2), and it is determined whether these values are below a predetermined threshold value (step S3). If this answer is No, then steps S4 to S7 described above are performed.
After calculating the three deviation amounts A, B, and C (step S2), it is determined whether these values are equal to or less than a predetermined threshold value (step S3). Then, this loop process is repeated until the determination in step S3 becomes affirmative, that is, Yes.

If the determination in step S3 is Yes, the three deviation amounts A, B, and C are below the threshold value, so the voltage setting of the secondary electron control electrode is completed (step S3).
8) The program ends.

In this way, based on the two reference voltages on the sample, two deviation amounts are set so that the three deviation amounts extracted from the secondary electron energy analysis curve become equal to or less than a predetermined threshold value.
The electron beam apparatus is automatically calibrated by adjusting each voltage of the secondary electron control electrode. Further, the reproducibility of the potential measurement value on the sample surface is good, the reliability is improved, and the measurement conditions can be automatically made the same even when there are a plurality of measurement points, and accurate measurement can be performed.

Further, since the automatic focus adjustment and the automatic beam position adjustment can be performed while the electron beam apparatus is being automatically calibrated, the efficiency of measuring the surface potential of the sample is improved.

In this embodiment, the pad of the clock signal line on the LSI mold is used as the reference voltage measurement point. However, the clock signal line itself may be used, or the power supply line or its pad may be used as shown in FIG. The applied voltage may be a high level reference voltage value, and the voltage applied to the ground line or its pad may be a low level reference voltage value.

Further, if a mechanism for correcting the drift of the beam irradiation point due to the voltage change of the primary electron control electrode is added on the basis of the cross-hair line process file (secondary electron signal data string), thin wiring can be achieved. It is possible to specify the voltage reference point.

[0053]

As described above, according to the first aspect of the present invention, a portion serving as a reference of electric potential is provided on the surface of a sample, and two two electric potentials, high and low, are measured at the portion. A plurality of deviation amounts are measured from the shape of the energy analysis curve of the secondary electrons, and the voltage value of the secondary electron control electrode is adjusted based on the deviation amounts so that the shape of the energy analysis curve becomes a constant shape. Since the signal processing means for setting is provided, the signal processing means can adjust the voltage applied to the secondary electron control electrode so that the shape of the energy distribution curve becomes constant.

Therefore, the electron beam apparatus is automatically calibrated, the reproducibility of the potential measurement value on the sample surface is good and the reliability is improved, and the measurement conditions are automatically the same even when there are a plurality of measurement points. It is possible to make accurate measurements.

According to a second aspect of the present invention, in the first aspect of the invention, as the plurality of deviation amounts, first, a difference between voltage values of the two energy analysis curves at a predetermined slice level, An amount obtained as a difference between two preset reference voltage values, secondly, a reciprocal value of the slope of each tangent line at the intersection of the slice level and the two energy analysis curves, and a third Since the value of the difference between the inclinations of the two tangent lines is used for the above, it is possible to surely make the shape of the energy analysis curve constant in a short time.

According to a third aspect of the present invention, in the first aspect of the present invention, the reference portion of the voltage is
Since the signal line for the clock signal of the integrated circuit or its pad is used, the high-level and low-level voltage values applied to these can be set to the high and low reference voltage values of the sample surface, and the reference voltage value can be set to the adjacent wiring. It can be set to a constant value without being affected by the potential of.

According to a fourth aspect of the present invention, in the first aspect of the invention, a portion serving as a reference of the voltage is
Since the voltage source line of the integrated circuit or its pad and the ground line or its pad are used, the high level voltage value applied to the voltage source line of the integrated circuit or its pad is set to the reference voltage value of the high potential of the sample surface potential, The low-level voltage value applied to the ground line or its pad can be set to the low reference voltage value of the sample surface potential, and the reference voltage value can be kept constant without being affected by the potential of the adjacent wiring. ..

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an electrode voltage automatic adjustment device for secondary electron control of an electron beam device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a deviation amount of an energy analysis curve of secondary electrons.

FIG. 3 is an explanatory diagram showing measurement points of a reference potential on an LSI mold.

FIG. 4 is a flowchart for explaining the operation of the secondary electron control electrode voltage automatic adjustment device of the electron beam device of FIG.

FIG. 5 is an overall configuration diagram of a conventional electron beam apparatus.

FIG. 6 is an explanatory diagram showing an energy distribution curve of secondary electrons.

FIG. 7 is an explanatory diagram showing an energy analysis curve of secondary electrons.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... Condenser lens 3 ... Reflector 4 ... Objective lens 4a ... Analysis grid 4b ... Buffer grid 5 ... Sample stage 6 ... Detector 6a ... Collector 9 ... Signal processing part 10 ... Control circuit

Claims (4)

[Claims] 1. A detector (6) for detecting secondary electrons generated when a sample is irradiated with an electron beam, and a secondary electron control electrode (3) for guiding the secondary electrons to the detector (6). , (6a), (4b), and a device for automatically adjusting an electrode voltage for secondary electron control of an electron beam device, comprising: a site serving as a reference of potential on the surface of a sample; A plurality of deviations are measured from the shapes of the energy analysis curves of two secondary electrons measured with respect to the electric potential,
A signal processing means for setting the voltage values of the secondary electron control electrodes (3), (6a) and (4b) based on these deviation amounts so that the shape of the energy analysis curve becomes a constant shape ( 9) and (10) are provided, The electrode voltage automatic adjustment device for secondary electron control of an electron beam device characterized by the above-mentioned. 2. As the plurality of deviation amounts, firstly, a difference between voltage values of the two energy analysis curves at a predetermined slice level and a difference between two preset reference voltage values are obtained as a difference between them. Using the calculated amount, secondly, the reciprocal value of the slope of each tangent line at the intersection of the slice level and the two energy analysis curves, and thirdly, the value of the difference between the slopes of the two tangent lines. 2. An electrode voltage automatic adjustment device for secondary electron control of an electron beam device according to claim 1. 3. The electrode voltage automatic adjustment for secondary electron control of an electron beam apparatus according to claim 1, wherein a signal line of a clock signal of an integrated circuit or a pad thereof is used as a portion that serves as a reference of the voltage. apparatus. 4. The secondary electron control of the electron beam apparatus according to claim 1, wherein a voltage source line of the integrated circuit or its pad and a ground line or its pad are used as the portion which becomes the reference of the voltage. Electrode voltage automatic adjustment device.