JPH0356878A - Electron beam device - Google Patents

Abstract

PURPOSE:To correct a frequency characteristic and to enhance the reliability of the measuring result by finding a corrected data of the frequency characteristic of the pulse generator output voltage for the generation of electron beam about plural frequencies. CONSTITUTION:The signal elements of output signals 66, 68 from the pulse generators 62, 64 are controlled by a pulse voltage control circuit 58 and simultaneously by a phase control circuit 78 its phase is controlled, and supplied to defectors 52, 54. In such a manner the electron beam 86 is scanned, and a measuring point 88 of a sample 70 is irradiated with the beam. On the other side, to a frequency counter 96, a sample operation clocking signal 76 is supplied from a sample driving circuit 72 and by this frequency counter 96, at the measuring time, the operation frequency of an operation signal 74 of the sample 70 is detected, and the frequency data 98 is supplied to a computer 56. By the computer 56, the corrected data of the frequency characteristic corresponding to this operation frequency is found from a memory 94, and based on this corrected data the frequency characteristic of the output voltage of the generators 62, 64 is corrected.

Description

[Detailed Description of the Invention] [Summary] Regarding an electron beam device, the objective is an electron beam device that can improve the reliability of measurement results regardless of changes in the operating frequency of a sample, and includes a deflector and an electron beam generator. An electron beam device that includes a pulse generator and irradiates a measurement point on a sample with an electron beam pulse synchronized with an operation signal of the sample in a controlled manner to measure a secondary electron signal obtained from the measurement point of the sample. means for obtaining correction data of the frequency characteristics of the output voltage of the electron beam generating pulse generator for a plurality of frequencies; a memory for storing the correction data; and a detector for detecting the operating frequency of the operating signal of the sample;
The apparatus is configured to include means for obtaining correction data of frequency characteristics corresponding to the operating frequency from the detector from the memory and correcting the frequency characteristics of the output voltage of the pulse generator for electron beam generation.

[Industrial application field]

The present invention relates to an electron beam device.

An electron beam device irradiates a measurement point on a sample with an electron beam pulse synchronized with an operation signal of the sample with phase control, and measures a secondary electron signal obtained from the measurement point on the sample. According to the electron beam device, it is possible to measure sample signals operating at high speed. This electron beam device uses a pulse generator for generating an electron beam, and the frequency characteristics of the output voltage of the pulse generator are constant. In such a case, if the operating frequency of the sample operating signal changes, the frequency and timing of generation of electron beam pulses will change depending on the operating frequency, reducing the reliability of the measurement results. Therefore, it is desired to improve the reliability of the measurement results by correcting the frequency characteristics of the output voltage of the pulse generator compared to the operating frequency of test t1.

[Conventional technology]

FIG. 4 shows the configuration of the electron beam pulse generator.

In FIG. 4, reference numerals 10 and 12 indicate pulse generators for generating electron beams.
, 12 are supplied with a trigger signal l4 from a phase control circuit (not shown in FIG. 4). The output signals 16, 18 from the pulse generators 10, 12 are supplied to electrostatic deflectors lO, 22, respectively, which deflectors 20, 22
As a result, the electron beam 24 is scanned by a diaphragm 26 . Then, the electron beam 24 is transmitted through the aperture hole 28 of the diaphragm 26.
The pulsed electron beam 24a reaches the measurement point 32 of the sample 3o only when it passes through the sample 3o.
0 measurement point 32 will be irradiated.

Incidentally, FIG. 5 shows the phase-voltage characteristics of the pulse generator output, and from FIG. 5 it can be seen that the electron beam pulse 24a
The timing of occurrence is understood.

[Problem to be solved by the invention]

In an electron beam apparatus, the voltage amplitude, voltage offset, etc. of the pulses generated by the pulse generator vary depending on the frequency. Therefore, when the operating frequency of the operating signal of the sample 30 changes, the following problem occurs. That is, sample 3
Due to the change in the operating frequency of the 0, the frequency of the bird changes, the generation intensity and timing of the electron beam pulse 24 change, and there are cases where the electron beam 24 does not pass through the aperture hole 28, which reduces the reliability of the measurement results. decreases.

In order to solve the above problem, it has been proposed to optimize the electron beam generation means (consisting of a pulse generator, deflector, etc.) while sampling the secondary electron signal. , there are reliability problems.

An object of the present invention is to provide an electron beam device that can improve the reliability of measurement results regardless of changes in the operating frequency of a sample.

[Means to solve the problem]

The present invention includes a deflector (52, 54) and a pulse generator (62, 64) for generating an electron beam, and includes a sample (70).
) is irradiated with an electron beam pulse (86) identical to the operation signal (74) of the sample (70) with phase control. )
In the electron beam device for measuring secondary electron signals obtained from the electron beam generator, the electron beam generation pulse generator (6
means (56, 90) for obtaining correction data for the frequency characteristics of the output voltage (2, 64) for a plurality of frequencies; a memory (94) for storing the correction data; Detector (96) that detects the operating frequency
and means for correcting the frequency characteristics of the output voltage of the electron beam generation pulsen energizer (62, 64) by obtaining correction data of the frequency characteristics corresponding to the operating frequency from the detector (96) from the memory (94). (65).

[Effect]

In the present invention, correction data of the frequency characteristics of the output voltage of the electron beam generation pulse energizer (62, 64) is obtained for a plurality of frequencies, and this correction data is stored in the memory (94). During measurement, the operating frequency of the operating signal (74) of the sample (70) is detected, and the correction data of the frequency characteristics corresponding to the detected operating frequency is stored in the memory (9).
4), and thereby correct the frequency characteristics of the output voltage of the electron beam generation pulse generator (62, 64).

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a circuit of an electron beam device according to an embodiment of the invention.

In FIG. 1, reference numeral 50 indicates an electron beam (E B) column, and the electron beam column 50 includes deflectors 52 and 54 therein. Further, numeral 56 indicates a calculator,
The calculator 56 sends a control signal 6 to the pulse voltage control circuit 58.
0 to a pulse generator 62 for generating an electron beam.
, 64 transmit the desired output signals 66, 68 to the deflector 52,
54. Note that the output signals 66, 68
For example, as shown in FIG. 2, the controlled elements include voltage amplitude, voltage offset, and pulse width.
There is one.

Reference numeral 70 indicates a sample, and an operation signal 74 is supplied to the sample 70 from a sample drive circuit 72.

A sample operation clock signal 76 is supplied from the sample drive circuit 74 to a phase control circuit 78, and a control signal 79 from the computer 56 and a clock signal 82 from an oscillator 80 are also supplied to the phase control circuit 78. Then, the phase control circuit 78 outputs a signal 84 based on the sample operation clock signal 76 and the clock signal 82, and the trigger signal 84 is synchronized with the designated signal and is shifted from the clock source by the designated phase. are pulse generators 62 and 64
supplied to The phase of the output signals 66 and 68 from the pulse generators 6 2 and 6 4 is controlled by this signal 84 .

As described above, the signal elements of the output signals 66 and 68 from the pulse generators 62 and 64 are controlled by the pulse voltage control circuit 58, and their phases are controlled by the phase control circuit 78. supplied to As a result, in the electron beam column 50, the electron beam 86 is scanned and irradiated onto the measurement location 88 of the sample 70.

A measuring device 90 such as a sampling oscilloscope is connected to the deflectors 52 and 54. This measuring device 90 measures the frequency characteristics of the output voltages of the pulse generators 62 and 64 for a plurality of frequencies, and supplies the measured data 92 to the computer 56. Calculator 56 calculates correction data for the frequency characteristics of the output voltages of pulse generators 62 and 64 for a plurality of frequencies based on measurement data 92, and stores the correction data in storage memory 94.

On the other hand, the frequency counter 96 is supplied with the sample operation clock signal 76 from the sample drive circuit 72, and the frequency counter 96 receives the operation signal 76 of the sample 70 during measurement.
detects the operating frequency of and supplies the operating frequency data 98 to the computer 56.

The calculator 56 obtains correction data of frequency characteristics corresponding to this operating frequency from the memory 94, corrects the control signal 60 to the pulse voltage control circuit 58 based on the correction data, and thereby the pulse generator 62, The frequency characteristics of the output voltage of 64 are corrected.

As described above, since the frequency characteristics of the output voltages of the pulse generators 62 and 64 are corrected based on the operating frequency of the sample 70, the generation intensity and timing of the electron beam pulses do not change, and as a result, the measurement The reliability of results can be improved.

Next, FIG. 3 shows a procedure for registering correction data.

In FIG. 3, starting with start 100, step {
In step 02, the oscillator is activated and a trigger input is made to the phase control circuit, and in step 104, the initial data of the EB (': quadruple beam) pulse is set.

The initial data are Al1ll110 (amplitude), 0 (offset), and Wid-0 (pulse If+-0 width).

It is set to 1-0 in step 106, and
8, if i>n (rh: set value), step 110
, the frequency f=f is set, and step 112, 1
Proceed to 14 and 116. In step 112, the voltage offset O adjustment change its amount is set to ΔO, and in step 114, the voltage offset O adjustment change amount is set to ΔA, and step mp
mppu11
6, the pulse width W adjustment change is set to ΔW1did. Then, in step 118, ΔOits ≦ε
. [[+” Ampl ampl' and ΔW1d≦
If εvid≦ε (ε0 mountain "ampl' wid setting value), return to step 112 and repeat this loop until convergence. Here, step 112, ↓14, 116
Three adjustment changes Δ0 1ΔA 1 and,
ΔWid is related to each other and may not be able to be operated independently. Therefore, change the value little by little until convergence, that is, ΔWid.
O ≦ε, ΔA ≦εlit all+
The operation is repeated until mpl aiplゝ and ΔW≦ε.

+d vid At step 118, once the loop converges, i.e. Δ
O ≦ε, ΔA ≦ε, and 11+ o
ff+mpl 21QP, ΔW ≦ε
If so, the process advances to step 120 and α is used as the correction data at the frequency f. 11, direct 1If lf+-O ampl (f”(f.
) = Δo-o, α 1 mpl mpl-1) wid (f” =
ΔWid=ΔA−A, α 1 ”id−G is stored in memory.

Thereafter, the process proceeds to step 112, where i=i+1, and then the process proceeds to step 108, and if i>n, the same procedure as above is repeated.

If i>rl in step 108, the process proceeds to step 124, and the correction data registration procedure ends.

As described above, each frequency f. Correction data will be stored for (i=0-n).

The frequency characteristics of the output voltage of the pulse generator are
Since it changes continuously, it is sufficient to perform the above correction data registration procedure for each frequency at an appropriate interval. In other words, even if the correction data corresponding to the sample operation clock signal measured by the frequency counter (numeral 96 in FIG. 1) is not stored in the memory, desired correction data can be obtained by complementary calculation from the registered correction data. can.

〔Effect of the invention〕

As explained above, according to the present invention, even if the operating frequency of the sample changes, the frequency characteristics of the output voltage of the pulse generator for electron beam generation are corrected, so the reliability of measurement results can be improved. can.

In addition, in the present invention, the correction operation is mainly based on calculation and does not require a measurement operation for correction.
It can be done quickly and stably.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an electron beam device according to an embodiment of the present invention, Fig. 2 is a waveform diagram showing elements of controlled pulses, Fig. 3 is a flowchart of the correction data registration procedure, and Fig. 4 is an electronic FIG. 5, which is an explanatory diagram of the configuration of the beam pulse device, is a phase-voltage characteristic diagram of the pulse generator output. 50... EB (electron beam) column 52, 54... Deflector 56... Computer 58... Pulse voltage control circuit 62, 64... Pulse generator for electron beam generation 70... Sample 2 ... Sample drive circuit 8 ... Phase control circuit 0 ... Oscillator 6 ... EB (electron beam) O ... Measuring device such as sampling oscilloscope 4 ... Correction data storage memory 6 ... Frequency Counters OO to 124...Waveform diagram showing elements of pulses controlled by step voltage. 2nd figure. 24: Explanatory diagram of structure of t-son beam electron beam pulse device. 4th figure. Output voltage. Phase of pulse generator output. 5th figure. Voltage characteristic diagram

Claims (1)

[Claims] It includes a deflector (52, 54) and a pulse generator (62, 64) for generating an electron beam, and transmits an operation signal of the sample (70) to a measurement point (88) of the sample (70). (7
4) In an electron beam device that measures a secondary electron signal obtained from a measurement point (88) of the sample (70) by irradiating it with an electron beam pulse (86) synchronized with the phase control,
means (56, 90) for obtaining correction data of the frequency characteristics of the output voltage of the electron beam generating pulse generator (62, 64) for a plurality of frequencies; a memory (94) for storing the correction data; and a sample (70).
) detects the operating frequency of the operating signal (74) of the detector (
96), and means (56) for obtaining frequency characteristic correction data from the memory (94) and correcting the frequency characteristic of the output voltage of the electron beam generation pulse generator (62, 64). Electron beam device.