JPS6248186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a backscattered electron detection means incorporated in a scanning electron microscope, an X-ray microanalyzer, etc., and a display device thereof.

When analyzing a sample using a scanning electron microscope, X-ray microanalyzer, etc., a relatively wide area on the sample surface is scanned with an electron beam, and low-magnification scanning secondary electron images, scanning backscattered electron images, etc. are observed. Points to be analyzed are determined by observing the microscopic image of the sample using an optical microscope. However, in such a method, in the process of determining the points to be analyzed,
There was a drawback that there were large differences based on the operator's experience, and trial and error had to be repeated.

The purpose of the present invention is to solve the above-mentioned drawbacks.The operator specifies conditions such as the rough composition and unevenness of the sample area to be analyzed, and only the area that meets the conditions is extracted. This feature is characterized in that it is displayed as follows. Generally, when a scanning electron microscope, an X-ray microanalyzer, or the like is used to analyze a sample, the following criteria may be used to select the target for analysis.

1. When the approximate composition of a certain phase in a sample is known and one wants to focus only on that phase and precisely measure the composition of that phase.

2. When attempting to measure only a specific region that differs from the general composition of the entire sample.

3. When the sample has unevenness and the unevenness should be avoided.

4. If the sample has irregularities and you are interested in these irregularities.

Accordingly, the present invention provides a sample analysis device for a scanning electron microscope, etc., which is capable of distinguishing and displaying areas that meet the conditions from other areas by an operator instructing the general composition and unevenness of the sample. is intended to provide.

Therefore, the present invention provides a means for converging an electron beam generated from an electron gun and irradiating it onto a sample surface, a means for scanning an electron beam irradiation position on the sample, and an electron beam for measuring the electron beam current irradiated onto the sample. A line current measuring means, a plurality of backscattered electron detection means for detecting backscattered electrons generated from the sample, means for obtaining a signal based on the composition of the sample and a signal based on the unevenness of the sample from the output of the backscattered electron detection means, and the composition means for obtaining a signal representing the average atomic number of the sample from a signal based on the signal and the output of the electron beam current measuring means, an output signal of the means for obtaining the signal representing the average atomic number, and a reference signal set to a desired value; and comparing the output of the means for obtaining a signal based on the unevenness of the sample with a reference signal and outputting a signal based on the results, and the output of the comparing means corresponds to the output of the scanning means. The present invention is characterized in that it is provided with a display means for displaying the same.

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a schematic diagram illustrating one embodiment of an apparatus according to the present invention. In the figure, reference numeral 1 indicates a vacuum lens barrel of a scanning electron microscope, and inside the lens barrel there is a condenser for irradiating a sample 5 held in a sample holder 4 with an electron beam 6 from an electron gun 2 in a narrowly focused state. Lens 3 etc. are stored. Furthermore, the electron beam 6 scans the sample surface two-dimensionally by a deflection system 7 to which an output signal from the scanning signal 8 is supplied, and a display means 9 such as a cathode ray tube or a typewriter synchronized with the scanning displays the sample. Information obtained by detecting the signal generated from 5 is displayed. Reference numerals 10a and 10b indicate backscattered electron beam detectors using a PN junction semiconductor, which are provided above the sample 5 at symmetrical positions with respect to the sample irradiation electron beam 6. The outputs of these detectors 10a and 10b are processed by a signal separator 11 having an addition/subtraction amplification function into a signal 12 based on the unevenness of the sample (hereinafter simply referred to as an unevenness signal) and a signal based on the composition of the sample (hereinafter simply referred to as a composition signal). It is separated into 13. One of the separated signals, the unevenness signal, is sent to the comparison circuit 15 via the discrimination circuit 14, and the other composition signal 13 is sent to the comparison circuit 15.
is sent to the signal conversion circuit 16. Reference numeral 17 denotes a Faraday cage held by the sample holder 4, and is configured to measure the electron current when the electron beam 6 is irradiated onto the Faraday cage 17 by operating the sample moving mechanisms 18a and 18b. The output of this Faraday cage is amplified by an amplifier 19 and then sent to the signal conversion circuit 16. The signal conversion circuit 16 calculates a backscattering coefficient by dividing the introduced sample irradiation current value and the composition signal 13. Further, the signal conversion circuit 16 stores in advance a function between the backscattering coefficient and the atomic number of the sample, and therefore, by determining the above-mentioned backscattering coefficient, the average atomic number of the sample is determined, and that value is The corresponding signal 20 is the comparator circuit 1
Sent to 5. The comparison circuit 15 compares the condition 21 specified by the operator with the discriminated unevenness signal 22 and the signal 20 corresponding to the average atomic number, and sends the signal to be analyzed to the display device 9. A central control circuit 23 is for automatically controlling the scanning circuit 8, comparison circuit 15, signal conversion circuit 16, sample moving mechanism 18b, etc. according to a preset program.

FIG. 2 is a schematic diagram showing a specific example of the comparison circuit 15 shown in FIG. The unevenness signal 22 discriminated by the discrimination circuit 14 indicates '0' when the sample is flat, and indicates '1' when the sample is concave or convex.
If the inverting circuits 24 and 25 receive a 0, they output a 1. The matching circuit 26 compares the output of the storage circuit 27 that stores the atomic number input by the operator with the signal 20 corresponding to the average atomic number of the sample obtained by the signal conversion circuit 16, and If they match, '1' is output, and if they do not match, '0' is output. The operator moves the changeover switch 28 to the a side when selecting a portion of the sample with no unevenness as an analysis target, and to the b side when selecting an uneven portion as an analysis target. The operator also moves the changeover switch 29 to the c side to select an area of the sample that matches the atomic number stored in the memory circuit 27 as an analysis target, and to the d side to select an area excluding the above area. The AND circuit 30 is for calculating the AND of the output of the changeover switch 28 and the output of the changeover switch 29 and outputting the result.

The operation of such a device will be explained in detail. First, the operator inputs the following items A to C as conditions 21 into the comparison circuit 15 and stores them.

A Atomic number of the sample of interest B Select the region of the atomic number of the sample of interest, or select the region excluding the region of the atomic number of the sample of interest. For example, to select the region of atomic number of interest, the selector switch 29 in FIG. 2 is turned to the c side.

C. Should you select a flat part of the sample or an uneven part of the sample? For example, if a flat portion is to be selected, the selector switch 28 in FIG. 2 is turned to a.

After setting these conditions, when the central control circuit 23 is activated, the Faraday cage 17 attached to the sample holder 4 is activated by a signal from the central control circuit.
The sample movement mechanism is controlled so that the electron beam irradiates the Faraday cage output at this time.
After being amplified in step 9, the signal is applied to a signal conversion circuit 16 and stored. Next, when the control for irradiating the target sample area with the electron beam by driving the sample moving mechanism while keeping the irradiation current constant under the electron beam sample irradiation conditions is completed, the central control circuit 23 The scanning signal power supply 8 is activated by the signal, and scanning of the sample by the electron beam 6 is started. Now the electron beam 6 is shown in Figure 3a.
If we scan in the direction of the arrow over the sample 5, which is composed of A phase and B phase with different elemental compositions and has irregularities as shown in , the backscattered electron beam detector 1 on the left side
A signal as shown by b in the figure is obtained from 0a, and a signal as shown by c in the figure is obtained from the backscattered electron beam detector 10b on the right side, and sent to the signal separator 11. By subtracting and adding these signals, a signal 12 based only on unevenness is obtained as shown by d in the figure.
As shown by e in the same figure, signal 1 based only on the composition
Separate into 3. The separated unevenness signal 12 is sent to the discrimination circuit 14, where it is discriminated as "1" or '0' depending on the presence or absence of unevenness, as shown by f in the figure, and then introduced into the comparison circuit 15. One composition signal is led to the signal conversion circuit 16, and a signal 20 corresponding to the average atomic number of the measurement sample is generated from the composition signal and the stored current value of the sample irradiation electron beam to the comparison circuit 16.
is sent to the matching circuit 26 at. At this time, the second
When the atomic number corresponding to the A phase is specified in the storage circuit 27 shown in the figure and the changeover switches 28 and 29 are set to the a side and the c side, respectively, the unevenness signal from the discrimination circuit 14 shown in FIG. 22 is inverted by an inverting circuit 24 and supplied to an AND circuit 30. Also, in the coincidence circuit 26, when the signal 20 corresponding to the average atomic number of the A phase is sent, it becomes '1'.
When a signal corresponding to the average atomic number of the B phase is sent, '0' is sent to the AND circuit 30.
Therefore, in the AND circuit, when a ``1'' is similarly inputted among the concavo-convex signal 22 and the signal 20 corresponding to the average atomic number, a ``1'' is sent to the display device 9, as shown in FIG. Only the flat part in the A-phase region is displayed. The area of the sample displayed in this manner clearly represents the target of analysis intended by the measurer at a glance, and is very effective as a means of searching for the target of analysis.

It should be noted that the present invention is not limited to the embodiments shown in FIGS. 1 and 2, and can be modified in various ways. For example, although the calculations in the signal conversion circuit are performed in an analog manner, they may be performed digitally after each input signal is A-D converted. Further, although the comparison circuit in FIG. 2 is constructed using only electronic circuits in this embodiment, it can also be constructed using a program using a digital computer.

As is clear from the above description, according to the present invention, an area that meets the conditions can be distinguished from other parts and displayed simply by an operator instructing the general composition and unevenness of the sample. A sample analysis device for a scanning electron microscope or the like is provided, and by viewing this display, it is possible to quickly set the electron beam irradiation position to a desired position on the sample when analyzing the sample.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention, FIG. 2 is a schematic diagram showing one embodiment of the comparison circuit in FIG. 1, and FIG. 3 is a diagram for explaining the operation of the present invention.
FIG. 4 is a schematic diagram showing an example of a display by the apparatus of FIG. 4... Sample holder, 5... Sample, 8... Scanning signal power supply, 9... Display means, 10a, 10b...
Backscattered electron detector, 11... Signal separator, 14...
Discrimination circuit, 15... Comparison circuit, 16... Signal conversion circuit, 17... Faraday cage, 18a, 18
b...Sample moving mechanism, 19...Amplifier, 23...
Central control circuit, 24 and 25... Inversion circuit, 26
... Matching circuit, 27 ... Memory circuit, 28 and 29
. . . Changeover switch, 30 . . . AND circuit.

Claims (1)

[Claims] 1. Means for converging the electron beam generated from an electron gun and irradiating it onto the sample surface, means for scanning the electron beam irradiation position on the sample, and electron beam current measuring means for measuring the electron beam current irradiated onto the sample. a plurality of backscattered electron detection means for detecting backscattered electrons generated from the sample; means for obtaining a signal based on the composition of the sample and a signal based on the unevenness of the sample from the output of the backscattered electron detection means; a signal based on the composition; means for obtaining a signal representing the average atomic number of the sample from the output of the electron beam current measuring means; comparing the output signal of the means for obtaining a signal representing the average atomic number with a reference signal set to a desired value; and Comparing means for comparing the output of the means for obtaining a signal based on the unevenness of the sample with a reference signal and outputting a signal based on the results, and displaying the output of the comparing means in correspondence with the output of the scanning means. A sample analysis device for a scanning electron microscope, etc., characterized by being provided with a display means.