JPH0782828B2 - Micro part analyzer - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus such as an electron beam microanalyzer for analyzing a fine particle or a minute region contained in a sample by exciting the sample with a microbeam and dispersing X-rays generated from the sample. .

B. Conventional technology When using a microbeam to analyze a minute portion of a sample, the microbeam irradiation position is fixed at the point where the sample is to be analyzed, but when the microbeam is used for fixed irradiation, the sample is heated. There is a case where the irradiation position becomes unstable due to thermal expansion due to heat, or charging and bending of the microbeam. Further, the irradiation position may be displaced due to the change over time of the device itself. It takes a considerable amount of time to analyze one minute area of a sample with an electron beam microanalyzer or the like, so if the irradiation point of the microbeam is displaced during that time, accurate analysis cannot be performed. This problem has a greater effect as the analysis area becomes smaller, and is a very important problem in the analysis of a minute area of a micro order or less.

For this reason, the conventional electron beam microanalyzer is used to
When performing line spectroscopic analysis, the analysis mode in which the microbeam is fixed and the scan confirmation mode in which the sample surface is scanned by the microbeam to form a sample image by secondary electrons from the sample are switched to the analysis mode. In the meantime, a method of manually switching to the confirmation mode, confirming the position of the particles being analyzed, and correcting the deviation of the microbeam irradiation point is adopted.

C. DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above-described conventional method for dealing with the movement of the microbeam irradiation point in the micro-region analysis of the sample by the microbeam, the confirmation and the correction of the positional deviation are not always performed during the analysis, Since it is only switched to the confirmation mode from time to time, it is unknown whether or not the irradiation point was stable between confirmations, and the reliability of the analysis results is reduced.

SUMMARY OF THE INVENTION The present invention aims to provide a micro-partial analyzer in which the conventional method can be used only for confirming and correcting the analysis position only occasionally so that the position confirming and correcting can be performed practically always.

D. Means for Solving Problems Micro-regions of a sample are irradiated with excitation rays, various secondary radiations emitted from the sample are analyzed, and appropriate radiations among the secondary radiations are constantly detected for monitoring. Then
When the detection signal changes, a small area including the irradiation point at that time is two-dimensionally scanned by the excitation line, the position where the detection intensity of the monitor radiation shows the original value is detected, and excitation is performed. The irradiation position of the line was corrected to that position.

E. When analyzing a microscopic area of a sample with an electron beam microanalyzer, etc., scan the sample surface to display a secondary electron image, find the particles to be analyzed, and fix the irradiation beam on the particles to fix the X-ray. Perform line spectroscopy analysis. At this time, for example, if the detection output is constantly monitored by using secondary electrons as monitoring radiation, the intensity of the monitor detection signal does not change unless the irradiation point of the electron beam is shifted, but the irradiation beam is the particle to be analyzed. The monitor output changes when it comes off.
The present invention detects this change and automatically starts scanning the small area of the sample surface, so that the operator actually switches to the confirmation mode from time to time, which means that confirmation is actually being performed at all times. Then, since scanning is performed in a small area including the analysis point, it is unlikely that other particles will enter the scanning range, and it is necessary to find a position where the monitor detection output shows the original value, which is the correct analysis. Since it is a point, the irradiation beam may be corrected to that position.

F. Embodiment FIG. 1 shows an apparatus according to an embodiment of the present invention. In this embodiment, a sample is irradiated with a microbeam of an electron beam, and X-rays emitted from the sample are dispersed to perform elemental analysis of fine particles in the sample.

In the figure, 1 is an electron gun, 2 is a condenser lens, 3 is an objective lens, and these portions form an electron beam microbeam B for irradiating the sample 4. Denoted at 5 is a deflection coil for deflecting the micro beam B.
It consists of two sets, one for directional scanning and the other for Y-direction scanning. Reference numeral 6 is an X-ray spectroscope crystal, and 7 is an X-ray detector, which are mechanically linked together with the microbeam irradiation point on the sample surface so as to be located on one Rowland circle. And the wavelength scanning of the detected X-rays is performed by moving the detector 7. A secondary electron detector 8 detects secondary electrons emitted from the microbeam irradiation point of the sample, and the detection output is input to the signal processing display device 10 through the amplifier, and the sample surface is scanned with the microbeam B. In that case, an image of secondary electrons on the sample surface is displayed by the signal processing display device. The video signal by the secondary electron which is the output of the signal processing display device controls the entire device.
It is designed to be taken in by the CPU. The output signal of the X-ray detector 7 is counted by the X-ray signal measuring device 12 via the amplifier 11, converted into the data of the count rate (count value in unit time, that is, X-ray intensity) and read by the CPU. It has become. CPU
Sends an X, Y synchronization signal to the raster generator 13 and causes the raster generator to form scanning signals in the X and Y directions.
The scanning signal is applied to the deflection coil 5 and the signal processing display device 10.
To enter.

An operation and an apparatus operation when analyzing fine particles in a sample with the above apparatus configuration will be described. First, the operator scans the sample surface two-dimensionally with the micro beam B and
An image by the next electron is displayed on the signal processing display device 10, fine particles to be analyzed are selected, and the sample position is adjusted so that the particle image comes to the center of the display surface, and then the X-ray spectroscopic analysis operation is started. Let FIG. 2 is a flowchart of the control operation of the CPU in this X-ray spectroscopic analysis operation.

When the analysis operation is started, first, the detection signal intensity So of the secondary electron detector 8 at that time is stored (a), the wavelength scanning of the X-ray spectrometer is started (b), and the X-ray intensity data is acquired and stored. (C) Then, the secondary electron detection signal S is taken in (d), and in the step (e), it is determined whether or not | S−So | ≦ reference value. If the determination is YES, wavelength scanning is performed. Is detected to have not reached the end (f), wavelength scanning is continued, and when the judgment in step (e) is NO, wavelength scanning is stopped (g) and acquisition of X-ray intensity data is also stopped. (H), scan the microscopic area of the sample surface with the microbeam, capture the secondary electron detection signal S (re), and detect (nu) the irradiation position of the microbeam where | S-So | <reference value. , Correct the irradiation position of the microbeam to that position. Specifically, the irradiation position of the microbeam is detected as the excitation current of the deflection coil 5, and the irradiation position is corrected by fixing the deflection coil excitation current detected in the step (n).
After that, the operation goes to step (f), and the wavelength scanning is restarted.

G. Effect In the present invention, the secondary radiation emitted from the sample irradiation point by the microbeam is detected and its detection intensity is monitored, and the change of the detection intensity detects the movement of the microbeam irradiation point on the sample. Then, if movement is detected,
It scans a small area of the sample surface with a microbeam to detect the correct irradiation position and corrects the beam irradiation point to that position, so the position is corrected immediately when a certain amount of analysis point movement is detected. Since the position is corrected and analyzed while monitoring the position, the operator's burden is not only reduced, but the position of the irradiation beam is stable compared to the conventional example in which confirmation operations are sometimes performed. The reliability and accuracy of analysis results can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention, and FIG. 2 is a flowchart of the operation of the CPU in the same embodiment. 4 ... Sample, 5 ... Deflection coil, 6 ... X-ray dispersive crystal,
7 ... X-ray detector, 8 ... Secondary electron detector, 10 ... Signal processing display device for secondary electron detection signal, 12 ... X-ray signal measuring device, 13 ... Raster generator.

Claims (1)

[Claims] 1. A means for scanning a sample surface with a microbeam, a means for detecting arbitrary secondary radiation for sample analysis emitted from a microbeam irradiation point on the sample surface, and a secondary radiation for other monitors. And a change in the detected intensity of the secondary radiation for monitoring, and when the change in intensity exceeds a reference value, a small area including a microbeam irradiation point on the sample surface is scanned with a microbeam. , For the above monitor 2
A micro-partial analyzer having a control means for detecting a microbeam irradiation position at which the detection intensity of the next radiation shows an original value or a value sufficiently close to the original value and correcting the microbeam irradiation point to that position.