JPH08273580A - Electronic probe micro analyzer with automatic focusing mechanism - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the increase of measurement time and unnecessary divergence of the stage so that measurement can be performed. [Constitution] Automatically moving a sample to a focus position by controlling a sample stage drive mechanism by a detection means for making light incident on a sample surface and detecting the reflected light, and a position control signal and a tracking control signal by the detection means. In an electronic probe microanalyzer with an automatic focusing mechanism, which comprises a focusing means and a measuring means for detecting a characteristic X-ray generated when the sample is irradiated with an electron beam at a focus position, the automatic focusing means comprises: The tracking control signal turns on / off the control of the sample stage drive mechanism according to the level of the reflected light from the sample.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electronic probe microanalyzer having an automatic focusing mechanism.

[0002]

2. Description of the Related Art In an electron probe microanalyzer (EPMA) equipped with a wavelength dispersive X-ray spectrometer (WDS), an analysis point, a center of a dispersive crystal, and a detector slit are located on one circle called a Roland circle. Need to be For this reason, in order to move the sample (analysis point) up and down and place it on the Rowland circle, a method of aligning with an optical microscope is adopted. Further, in recent years, for the purpose of aligning a sample using this optical microscope, an automatic focusing mechanism is incorporated to measure the direction and amount of deviation from the in-focus position of the sample surface, and based on this information, the vertical position of the sample (Z There is a method in which the position) is automatically adjusted, and the sample surface (analysis point) is always kept aligned (following operation) with the focus position of the X-ray optical system according to the change in the height of the sample. As a result, the measurement signal is continuously sampled while driving the sample in the horizontal direction (X, Y directions) to obtain a linear (line analysis) or two-dimensional (area analysis) signal distribution on the sample. be able to.

[0003]

Generally, since the automatic focusing mechanism controls the Z position by using the reflected light from the sample, when the sample is driven in the horizontal direction, the reflectance on the sample is reduced. If the value changes rapidly and the value drops sharply, the automatic focusing mechanism may not be able to recognize the focus position or the direction and amount of the shift at that point. If you try to continue the focusing operation in this state, it takes a very long time to focus, and the overall measurement time becomes unnaturally long, or in some cases the automatic focusing operation diverges, causing It may be dangerous to reach the limit of movement. Therefore, it is difficult to deal with a sample whose reflectance changes greatly on the sample. The present invention has been made in view of such circumstances, and an object of the present invention is to provide an electronic probe microanalyzer with an automatic focusing mechanism that can prevent an increase in measurement time and unnecessary divergence of a stage.

[0004]

According to the present invention, a sample stage driving mechanism is controlled by a detecting means for making light incident on a sample surface and detecting the reflected light, a position control signal by the detecting means, and a follow-up control signal. Electron probe micro with an automatic focusing mechanism including automatic focusing means for moving the sample to the in-focus position and measuring means for detecting characteristic X-rays generated when the sample is irradiated with the electron beam at the in-focus position. In the analyzer, the automatic focusing means turns ON / OFF the control of the sample stage drive mechanism according to the level of the reflected light from the sample by the follow-up control signal.

[0005]

The present invention is an EPMA having an automatic focusing mechanism.
In the case of continuously sampling the measurement signal while driving the sample, the sample position tracking operation and the Z position of the stage are controlled according to the reflectance of the sample to increase the measurement time and unnecessary divergence of the stage operation. Can be prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a configuration example of the present invention. In the figure, 1 is an electron beam, 2 is a sample, 3 is a characteristic X-ray, and 4 is a WD.
S, 5 is a dispersive crystal, 6 is a detector, 7 is a WDS measurement system, 8
Is an optical microscope illumination, 9a is incident light, 9b is reflected light, 10
Is an optical microscope, 11 is a sensor, 12 is an autofocus device, 1
3 is a stage drive mechanism, 14 is a stage, 15 is a controller, and 16 is a measurement controller. In the figure, when the sample 2 is irradiated with the electron beam 1, the characteristic X-ray 3 is generated, and the WDS
It is incident on 4. In the WDS 4, the characteristic X-rays 3 are separated by the dispersive crystal 5, detected by the detector 6, and counted by the WDS measuring system 7 (composed of an amplifier, a timer, a counter, etc.).

On the other hand, the automatic focusing device 12 makes the incident light 9a incident on the sample 2 by the optical microscope illumination 8 and guides the reflected light 9b reflected to the sensor 11 through the optical microscope 10. A position control signal and a tracking control signal are output from the sensor 11,
The autofocus position 12 drives the stage 14 via the stage drive mechanism 13. The position control signal is a control signal for designating in which direction and how much the sample stage is moved, based on the direction and amount of deviation from the in-focus position of the sample. Further, the follow-up control signal is a control signal that turns on the follow-up when the threshold value is above a certain threshold and turns off the follow-up control signal when it is below a certain threshold according to the intensity of the reflected light from the sample.

The sensor 11 which outputs a position control signal and a tracking control signal, for example, splits the reflected light from the sample surface into two optical paths and makes it enter the line sensor, and when the sample is at the in-focus position, The image forming position of the optical system in one optical path and the image forming position of the optical system in the other optical path are set to the same distance on the opposite side of the line sensor from each other, and the height of the sample surface changes. Since the intensity of light incident on the line sensor in both optical paths changes so that if one increases, the other decreases, the difference signal is used as a position control signal, and the amount of light received in both optical paths is changed by the change in reflected light intensity. Since it changes equally, the signal can be used as a tracking control signal. Further, as the sensor 11, the laser beam is obliquely incident on the sample surface, the height of the sample surface is converted into an angle change of the reflected beam, and the angle change is detected by a line sensor to be used as a position control signal. A part of the light may be received by a photomultiplier and converted into an electric signal according to the intensity of reflected light to be used as a tracking control signal.

The analysis point stage drive mechanism 13 is also driven by a manual operation from the controller 15 when an analysis point is input. The optical axis of the electron beam 1 coincides with the optical axis of the optical microscope 10, and the focus of the WDS 4 is also the optical microscope 10.
Is adjusted to match the focus of the. The measurement control device 16 drives and controls the automatic focusing device 12, receives a signal indicating whether or not focusing is performed from the automatic focusing device 12, and starts counting of the WDS measuring system 7 when focusing is performed. Further, the drive control of the stage drive mechanism 13 is performed.

Next, the operation of the present invention will be described with reference to FIG. 2 by taking the case of surface analysis as an example. FIG. 2 is a diagram for explaining the timing of tracking control by the automatic focusing device.
At the time of actual measurement, while the stage driving mechanism 13 drives the stage 14 in a certain direction, the automatic focusing device 12 constantly forms the Roland circle formed by the analysis point on the sample 2, the center of the dispersive crystal 5, and the center of the slit of the detector 6. Control is performed so as to be positioned above, and at the same time, continuous sampling is performed by the WDS measurement system 7. For example, as shown in FIG. 2A, if there are two dark areas indicated by diagonal lines on the sample surface and the measurement scan line passes through these areas, the tracking based on the reflected light intensity is performed. The control sensor signal changes as shown in FIG. Depending on whether the sensor signal for tracking control is larger or smaller than the threshold value, FIG.
As shown in (c), the automatic focusing device turns on / off the tracking function. By such control, the reflectance of the sample surface becomes small, and even if the sensor cannot read the position correctly, the automatic focusing device does not move the Z position. When the reflectance of the sample is recovered and the signal to the sensor exceeds the threshold value, the tracking operation is started again. As a result, it is possible to prevent an increase in measurement time and unnecessary divergence of stage operation, and to perform measurement quickly and safely.

In the above description, the threshold value of the tracking control sensor signal is a fixed value, but it may be varied according to the sample to be measured and the purpose. In the above example, when the reflectance on the sample becomes low, the tracking operation is simply turned off,
Although the Z position of the stage is not moved, when the reflectance of the sample becomes lower than a certain threshold value, the operation start position is set to return to a certain point (for example, the center of the driving range in the Z direction). You may choose arbitrarily.

[0012]

As described above, according to the present invention, in the EPMA incorporating the automatic focusing mechanism, the reflectance of the sample is increased when sampling is performed while driving the stage, such as line analysis and surface analysis. By controlling the follow-up operation and the Z position of the stage according to the above, the reflectance of the sample surface is drastically changed and the deviation of the in-focus position cannot be accurately grasped, without increasing the measurement time unnecessarily, and It is possible to safely measure.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of the present invention.

FIG. 2 is a diagram illustrating the timing of follow-up control.

[Explanation of symbols]

1 ... Electron beam, 2 ... Sample, 3 ... Characteristic X-ray, 4 ... WDS, 5
... dispersive crystal, 6 ... detector, 7 ... WDS measurement system, 8 ... optical microscope illumination, 9a ... incident light, 9b ... reflected light, 10 ... optical microscope, 11 ... sensor, 12 ... autofocus device, 13 ... stage drive Mechanism, 14 ... Stage, 15 ... Controller, 16 ... Measurement control device.

Claims (1)

[Claims] 1. A sample stage drive mechanism is controlled by a detection means for making light incident on a sample surface and detecting reflected light thereof, a position control signal by the detection means, and a follow-up control signal to move the sample to a focus position. In the electronic probe microanalyzer with an automatic focusing mechanism, the automatic focusing means is provided with an automatic focusing means for controlling and a measuring means for detecting a characteristic X-ray generated when the sample is irradiated with an electron beam at a focusing position. Is an electronic probe microanalyzer with an automatic focusing mechanism, which controls ON / OFF of the sample stage drive mechanism according to the level of reflected light from the sample by a tracking control signal.