JPH0128461B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for measuring a sample by irradiating the sample with an electron beam and detecting the X-rays generated by the sample.

[Prior art] In analytical electron microscopes, etc., a sample stage on which a sample is placed is moved two-dimensionally, and the sample is irradiated with an electron beam, resulting in X-rays generated from the sample.
The rays are guided through a spectroscopic crystal to an X-ray detector to analyze the sample two-dimensionally. by the way,
After polishing the sample surface in order to set the position of the sample surface in the optical axis direction where the electron beam is irradiated to the correct position,
Although the sample is set in the sample chamber, it is difficult to remove even the slightest undulations on the sample surface even by polishing. Due to such undulations, if the position of the optical axis direction of the sample surface, which is the point of generation of X-rays, deviates from the normal position, the detected intensity of the X-rays will be lower than that in Figure 1 compared to when it is at the normal position. As shown, it becomes smaller. In other words, assuming that the z coordinate (coordinate in the optical axis direction) of the surface of the sample is z = z ₀ + δz, which is shifted by δz from the normal coordinate Z ₀ , the actually detected intensity I(z) is For example, using the true detection strength I ₀ , it can be expressed approximately as follows, and the detected X
The intensity of the line will contain errors.

I(z)=I ₀ −A·δz ² However, in the above equation, A is a positive proportionality constant.

[Object of the Invention] The present invention solves these conventional drawbacks, and even when the position of the sample in the optical axis direction is not at the normal position,
The purpose is to provide a device that can perform error-free measurements.

[Structure of the Invention] The present invention irradiates a sample with an electron beam, guides the X-rays generated from the sample through a spectroscopic crystal to an X-ray detector, and detects the irradiation point of the electron beam. In this method, the position of the surface of the sample in the optical axis direction is measured during or before and after the measurement, and the X-ray detection is performed based on a signal representing the position. The feature is that the intensity is corrected.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 2 is for showing an example of an apparatus for carrying out the present invention. In the figure, 1 is an electron gun, and after the electron beam 2 from this electron gun 1 is focused by a focusing lens 3, it is further The light is narrowed down by the objective lens 4 and irradiated onto the sample 5. Sample 5 is sample stage 6
By rotating step motors 7X, 7Y, and 7Z, this sample stage can be moved by arbitrary amounts in the X and Y directions perpendicular to the optical axis, and in the Z direction along the optical axis. I'm starting to be able to do it. 8 is a drive pulse generation circuit, and this drive pulse generation circuit 8 operates the step motors 7X, 7 based on a control signal from an arithmetic and control unit 9.
Generate drive pulses to rotate Y and 7Z. Reference numeral 10 denotes a spectroscopic crystal for selecting only a specific wavelength component of the X-rays 11 generated from the sample 5 when the sample 5 is irradiated with the electron beam 2 and guiding it to the X-ray detector 12 . The output signal of the X-ray detector 12 is amplified by the amplifier 13 and then counted by the counting circuit 14, and this count value signal is supplied to the arithmetic and control unit 9. 15 is an illumination light source that generates illumination light for observing the surface of the sample 5;
The light is transmitted through the semi-transparent mirror 16, the prism 17, the first
The sample 5 is irradiated via the second spherical mirrors 18 and 19. 20 are the first and second spherical mirrors 18 and 19
Together with this lens, it constitutes an optical microscope for observing the surface of the sample 5. Light from the surface of the sample 5 passes through the first and second spherical mirrors 18, 19 and the prism 1.
7 and enters the lens 20. This optical microscope is adjusted so that a sharp image can be obtained only when the sample surface is placed at a proper position in the optical axis direction. Further, 21 is an input device for inputting various commands to the arithmetic and control unit 9. Further, the arithmetic and control unit 9 is connected to a memory 22 for storing the z-coordinate of each point on the sample surface. 2
3 is a display device.

Using the apparatus with such a configuration, first, the input device 21 is used to input the third data that is two-dimensionally distributed on the sample 5.
A command is given to the arithmetic and control unit 9 so that each point indicated by an x mark in the figure is sequentially arranged directly under the optical axis. As a result, based on the control signal from the arithmetic and control device 9, the drive pulse generation circuit 8 outputs the step mode 7.
The pulses supplied to X and 7Y are controlled, and the sample stage 6 is moved so that each of the above points is sequentially placed directly below the optical axis. Therefore, each time the sample stage 6 moves and each point is placed directly under the optical axis, the operator operates the input device 21 while observing the sample surface through the lens 20 to move the sample 5 in the optical axis direction, that is, the Z axis. Move the specimen slightly in the direction so that the sample surface can be observed clearly. Along with this operation, the arithmetic and control unit 9 grasps how much the sample 5 has moved from the regular z-coordinate position _z0 as a result of this movement from the number of pulses supplied to the step motor 7Z, and calculates the light at this point. The axial position (i.e. Z coordinate) is stored in the memory 22.
is stored in the memory address corresponding to the position coordinates (xi, yi). After completing the measurement at the first measurement point,
The operator operates the input device 8 to move the sample stage so that the next measurement point is placed directly below the optical axis, and stores the position of this point in the optical axis direction in the memory 22 as in the case described above. do. In this way,
Measure the z-coordinates of all the points indicated by x marks in Fig. 3, and store this measured value data in this memory 2.
2, start the actual analysis. Now, for example, the coordinates perpendicular to the optical axis are (xa, ya)
This will be explained by taking as an example a case where X-ray analysis is performed at a certain point. First, an instruction is given using the input device 21 so that the point at these coordinates is placed directly below the optical axis. As a result, as in the case described above, the sample stage 6 moves to a position where the electron beam 2 is irradiated at the coordinates (xa, ya). Therefore, X-rays are generated from this point, and this X-ray 11 enters the X-ray detector 12 via the spectroscopic crystal 10 and is detected, and this detection signal is amplified in the amplifier 13 and then sent to the counting circuit 14. , and is supplied to the arithmetic and control unit 9 as a signal with the intensity Ia, for example. The arithmetic and control unit 9 uses data representing the z-coordinate value at each of the discretely taken coordinates (xi, yi) stored in the memory 22 to calculate the coordinates (xa, yi).
ya) using the interpolation method. Assuming that the height determined in this way is za = z ₀ + δza, the arithmetic and control unit 9 performs calculations to determine the true intensity I ₀ at this time from Ia and δza, and calculates the true intensity as the true intensity. Calculate Ia + Aδza ² .
As a result, the display device 25 displays this corrected value.

It should be noted that the above-described embodiment is only one embodiment of the present invention, and many other embodiments may be adopted when implementing the present invention.

For example, in the above-mentioned embodiment, an example was explained in which the detection intensity at one analysis point was measured, but it can be similarly applied to the case where the sample stage 6 is moved two-dimensionally to obtain a two-dimensional image of the sample. In that case, the z-coordinate of each point is determined, and based on the data representing this z-coordinate, as explained in the previous example, calculations are performed to determine the true intensity from the actually obtained detection intensity. It is sufficient to perform this for each of these points.

In addition, in the above embodiment, the z-coordinate of the sample surface was measured by observing the sample surface with an optical microscope while moving the sample surface in the optical axis direction. The height of the sample surface may be measured using a height detector.

Furthermore, in the above-described embodiments, the z-coordinate was measured prior to the actual analysis, but it may be performed during or after the analysis.

Furthermore, in the above embodiment, a quadratic expression regarding z was used as an expression to express the relationship between the true detection intensity and the actual detection intensity to determine the true intensity, but a higher-order expression may be used. May be used.

[Effects] As is clear from the above description, according to the present invention, accurate X-ray intensity can be measured even for a sample whose surface position is deviated from the normal position.

[Brief explanation of drawings]

Figure 1 is a diagram to explain how the detected intensity of X-rays decreases when the z-coordinate of the sample surface deviates from the normal position, and Figure 2 is an example of an apparatus for implementing the present invention. FIG. 3 is a diagram for explaining each point two-dimensionally distributed on the sample surface whose z-coordinate is to be measured. 1: Electron gun, 2: Electron beam, 3: Focusing lens,
4: Objective lens, 5: Sample, 6: Sample stage,
7X, 7Y: Step motor, 8: Drive pulse generation circuit, 9: Arithmetic control unit, 10: Spectroscopic crystal, 1
1: X-ray, 12: X-ray detector, 13: Amplifier, 1
4: Counting circuit, 15: Irradiation light source, 16: Semi-transparent mirror, 17: Prism, 18, 19: Reflector, 2
0: Lens, 21: Input device, 22: Memory,
23: Display device.

Claims (1)

[Claims] 1 A sample is irradiated with an electron beam, and the X-rays generated from the sample by the irradiation of the electron beam are transmitted through a spectroscopic crystal.
In the method of measuring the detected intensity of X-rays at the irradiation point of the electron beam, the position of the surface of the sample in the optical axis direction is measured during or before and after the measurement. , an X-ray measurement method using an electron beam apparatus, characterized in that the X-ray detection intensity is corrected based on a signal representing the position.