JPS6352424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for correcting variations in sample surface position due to sample movement in an X-ray microanalyzer (XMA).

[Prior art]

In XMA, area analysis is used as one of the methods to measure the element distribution on the sample surface. This surface analysis method uses a computer to control the XMA, moves the sample irradiated with the electron beam two-dimensionally, and converts the X-rays emitted from the surface of the sample by the electron beam into a wavelength-dispersive type. It is detected by an X-ray spectrometer and displayed as a brightness modulated image on a CRT screen, for example. In analysis using this wavelength-dispersive X-ray spectrometer, it is necessary to maintain a constant positional relationship between the electron beam irradiation point (i.e., X-ray generation point) on the sample surface and the spectrometer.
The sample surface is set on a sample stage so that the surface of the sample polished into a flat surface is perpendicular to the Z-axis, and the sample surface is moved within a plane perpendicular to the Z-axis. Therefore, the sample stage is equipped with an X-axis drive mechanism and a Y-axis drive mechanism that move the sample in the X-axis direction perpendicular to the Z-axis and the Y-axis direction perpendicular to the Z-axis and the X-axis. Furthermore, a Z-axis moving mechanism for moving the sample in the Z-axis direction is provided, and the height of this Z-axis drive mechanism is adjusted so that the optimal position is set when the sample is set on the sample stage. This height adjustment can be done by, for example, monitoring the X-ray detection output from an X-ray spectrometer while irradiating the sample with an electron beam, and then moving the sample up and down using the Z-axis drive mechanism to find the position where the maximum output value is obtained. This is done by setting the sample height to . After completing such height adjustment, the aforementioned X-axis drive mechanism and Y-axis drive mechanism are controlled by scanning signals to perform two-dimensional scanning on the sample surface with the electron beam. However, if the moving direction of the sample stage is not strictly perpendicular to the Z-axis, or if the sample is not set correctly on the sample stage, the sample irradiated by the electron beam may be affected by the movement of the sample stage. The coordinate of the surface position in the Z-axis direction changes, and the generation point of the X-rays incident on the spectrometer is no longer kept constant. In order to eliminate such fluctuations in the X-ray generation point, conventionally, the optimal Z-axis coordinates are determined by height adjustment as described above for each point on the sample surface to be analyzed by X-rays, and then the X and Y axes are driven. The Z-axis coordinates are stored in correspondence with the X and Y coordinates of the mechanism, and the stored Z-axis coordinates are read out for each measurement location.
A method of controlling a shaft drive mechanism has been proposed. Although this type of control method makes it possible to correct the sample position, it requires a large amount of storage capacity, and since each point is read and controlled, the movement speed is slow, making it difficult to collect data for the entire measurement area. The disadvantage is that it takes a huge amount of time.

[Purpose of the invention]

It is an object of the present invention to eliminate the above-mentioned drawbacks, speed up the collection of X-ray data, and provide a simple correction method for eliminating the influence of variations in the sample surface position during sample movement.

[Structure of the invention]

In the present invention, the sample is repeatedly moved back and forth in the X-axis direction by a fixed amount, and each time the sample is
In a method of measuring the X-ray intensity distribution in a two-dimensional area of the sample surface by moving it a certain amount in the Y-axis direction perpendicular to the axial direction, it is optimal for the X-ray spectrometer to measure the X-ray intensity distribution at multiple locations on the sample surface in advance. The present invention is characterized in that the coordinates of the Z-axis are measured in advance, and the sample is continuously moved in the Z-axis direction during the movement period in each of the X-axis directions at a constant rate of change determined from the measured values.

[Principle of the invention]

In the present invention, minute irregularities on the sample surface are
This is based on the premise that the sample surface is polished to a value sufficiently smaller than the tolerance in the Z-axis direction for surface analysis, and that the sample surface is formed into a substantially perfect plane. If we consider the sample surface to be a nearly perfect plane, we can adjust the Z height at several points within the measurement range in advance.
By determining the optimum value of the axis position, the degree of inclination of the sample plane from the plane perpendicular to the Z-axis can be determined by calculation. Therefore, if the Z-axis moving mechanism is driven at a constant speed to cancel the position change in the Z-axis direction due to the tilting during the movement and scanning of the sample, the displacement of the sample in the Z-axis direction can be easily corrected. It becomes possible to do so.

〔Example〕

The method of the present invention will be explained below using the drawings.
FIG. 1 is a schematic diagram of an XMA that implements the method of the present invention. 1 is an electron beam, and the electron beam 1 is focused onto the surface of a sample 3 by an objective lens 2 .
The sample 3 is placed on a sample stage 4, and an X-axis drive mechanism 5, a Y-axis drive mechanism 6, and a Z-axis drive mechanism 7 are attached to the sample stage 4. Independent drive units 8, 9, and 10 are connected to each of the X, Y, and Z axis drive mechanisms, and are configured to be driven independently by drive command signals from the control device 11. There is. 12 controls the sample stage 4 through the control device 11 in X, Y and Z.
This is a manual operating device for manually moving the axis. 1
3 is a spectroscopic crystal for condensing X-rays 14 emitted when the sample 3 is irradiated with the electron beam 1;
It is detected by the X-ray detector 15. Also, X-ray detector 1
The intensity of the X-rays detected by 5 is converted into an electric signal (pulse), then measured by an X-ray measurement circuit 16, and sent to the screen of a cathode ray tube (CRT) 17 as a brightness modulation signal via a control device 11. will be displayed.
18 is a storage device for storing X-ray data. 19 is an optical microscope as a means for observing the entire surface of the sample 3, and this optical microscope includes an illumination lamp 20, a half mirror 21, a mirror 22,
It is composed of a concave mirror 23, a convex mirror 24, and an eyepiece lens barrel 25, and is arranged near the objective lens 2 without blocking the electron beam path.

In the apparatus configured as described above, a method for moving a sample when performing surface analysis using the apparatus will be described. First, the surface of the sample 3 is polished as much as possible so that the surface irregularities are sufficiently smaller than the error in the Z-axis direction (for example, ±20 μm maximum) allowed for surface analysis, and then fixed on the sample stage 4. Here, the second
As shown in the figure, for example, it is assumed that an X-ray area analysis is performed on a rectangular region S within the surface of the sample 3. First, the four corner neighborhoods A, B,
Find the optimal Z-axis coordinates for points C and D using the Z-axis moving mechanism. In addition to the height adjustment method described above, the following method of using an optical microscope (OM) can be used to find the optimal value of the Z-axis coordinate.
That is, the Z-axis moving mechanism 7 is set to the optimum state with respect to one point on the sample, for example, point A, by the above-mentioned height adjustment using a manual operation device, and the Z-axis coordinate (Za) at that time is stored in the storage device 18. to be memorized. Then, in this state, the sample surface is observed using the OM, and the OM is focused. Next, point B on the sample is moved to the electron beam irradiation position by the X and Y axis movement mechanism,
While the focusing means of the OM remains fixed, the Z-axis moving mechanism is changed to focus the OM image, and the Z-axis coordinate (Zb) at this time is stored. This is OM
The optimum Z-axis coordinates (Zc) and (Zd) for points C and D are obtained and stored by repeating similar operations.

Scanning for surface analysis is performed by moving the sample stage 4 stepwise from point A to point B, that is, in the X-axis direction, using point A on the surface of the sample 3 as a base point, and during this movement period, the The radiation intensity is detected by the X-ray detector 15 and stored in the storage device 18 via the control device 11. When the measurement for one row on the X-axis is completed, the X-ray detector 1 is moved one step in the Y-axis direction, and the step-like scanning in the X-axis direction as described above is repeated to move the X-ray detector 1 at each coordinate position.
5 is stored in the storage device 18. Then, by repeating the same operation, finally the area S
The measurement of the X-ray intensity distribution within is completed.

Now, the driving speed by the X-axis moving mechanism 6 is Vx, the driving speed by the Z-axis moving mechanism 7 required for height correction between points A and B is V'z, the length between points A and B is Lx, and the point
If the length between AC is Ly, the following relational expression holds true.

V'z=Zb-Za/Lx Also, the driving speed Vz by the Z-axis moving mechanism 7 required for height correction along the X-axis at an arbitrary Y-coordinate position (y)
is expressed by the following relational expression.

Vz={(Zb−Za)+(Zd−Zb−Zc+Za)y
/Ly}/LxVx Therefore, if the Z-axis moving mechanism 7 is driven at a speed Vz that satisfies the above formula every time a stepwise scan in the X-axis direction is performed, the height can be corrected over the entire measurement area S. It can be performed. The control device 11 in the XMA of FIG. 1 is given in advance a program for calculating the speed Vz that satisfies the above equation, and is configured to calculate the speed Vz for each repeated scan.

〔effect〕

As described above, according to the present invention, when performing two-dimensional surface analysis of a sample with an It is possible to provide a method for moving a sample in an X-ray microanalyzer or the like that can easily keep the time required for data collection constant without significantly increasing the time required for data collection.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an apparatus to which the method of the present invention is applied, and FIG. 2 is a diagram for explaining the method of the present invention. 1: Electron beam, 2: Objective lens, 3: Sample, 4:
Sample stage, 5: X-axis drive mechanism, 6: Y-axis drive mechanism, 7: Z-axis drive mechanism, 8: X-axis drive section, 9:
Y-axis drive section, 10: Z-axis drive section, 11: Control device, 12: Manual operation device, 13: Spectroscopic crystal, 14:
X-ray, 15: X-ray detector, 16: X-ray measurement circuit,
17: CRT, 18: Storage device, 19: Optical microscope, 20: Lamp, 21: Half mirror, 22:
Mirror, 23: Concave mirror, 24: Convex mirror, 25: Eyepiece lens barrel.

Claims (1)

[Claims] 1 Place the sample in the X-axis direction perpendicular to the optical axis (Z-axis) and the
In a method in which the sample is moved in the Y-axis direction perpendicular to the axial direction, the sample is irradiated with an electron beam, and the X-rays from the sample surface irradiated with the electron beam are measured using a wavelength-dispersive X-ray spectrometer. The optimal Z-axis position of the sample with respect to the X-ray spectrometer is measured at multiple locations on the sample surface, and during the period of movement of the sample in the X-axis direction, the position is determined at a constant speed determined from the measured values. A method for moving a sample in an X-ray microanalyzer, characterized in that the sample is moved in the Z-axis direction.