KR100346409B1 - Stage driving method of electron probe micro analyzer - Google Patents

Abstract

The present invention is to control the height of the Z-axis with high accuracy to always meet the condensing conditions of the X-ray spectrometer in the line analysis or mapping analysis of the uneven surface, the sample stage based on a predetermined condition in the line analysis or mapping analysis The Z-axis coordinates in the height direction of C are corrected, the Z-axis coordinates driven during the analysis are defined as a step function, and the Z-axis coordinate values are sequentially controlled based on the Z-axis correction function of the step shape. The Z-axis correction value of the sample stage that satisfies the condensing conditions of the X-ray spectrometer at each analysis position of the step is provided as a step-shaped Z-axis correction function. Obtain the Z-axis correction value at the analysis position in the direction and drive the Z-axis of the sample stage to the obtained Z-axis correction value.

Description

Stage driving method of electron probe micro analyzer

The present invention relates to a control method of an electronic probe microanalyzer, and more particularly, to a drive control method in the height direction of a sample stage.

In the Electron Probe Microanalyzer (EPMA) using a wavelength-dispersive spectrometer, the X-ray spectrometer of a sample, a spectral crystal, and a detector is a condensing condition for detecting characteristic X-rays emitted from a sample by electron beam irradiation. It is required to arrange the columnar with high accuracy. Usually, condensing conditions of this X-ray spectrometer are performed by aligning the height of a sample surface.

In surface analysis using an electronic probe microanalyzer, etc., one-dimensional or two-dimensional distribution of an X-ray signal is obtained by detecting an X-ray signal at each time while changing the analysis position one by one in addition to the point analysis that analyzes a point of a sample surface. There is a line analysis or mapping analysis.

In line analysis or mapping analysis, the sample is moved at a constant speed on the X and Y planes, and the X-ray signal is measured at regular intervals between the movements. In the case of performing line analysis or mapping analysis on the uneven surface of the sample, the height of the sample surface at the analysis position changes as the sample moves on the X and Y planes. Therefore, in order to perform highly accurate measurement, it is always necessary to control the height direction of a sample stage so that the height of a sample surface at each analysis position may satisfy the condensing conditions of an X-ray spectrometer.

In addition, as a method of controlling the height direction of the conventional sample stage, the actual value or approximation of the Z-axis coordinate value of the sample stage when the height of the sample surface satisfies the X-ray condensing condition is obtained in advance over the entire analysis area. The method of controlling the Z-axis coordinate of a sample stage is known based on the obtained Z-axis coordinate value.

Conventionally, as a driving method for controlling the Z-axis coordinates of a sample stage, the entire analysis area is approximated to one plane, and the Z-axis is moved at a constant speed with respect to a constant speed movement in the X and Y-axis directions so as to meet the inclination of the plane. Driving methods are known.

The driving method of approximating the whole analysis area to one plane and moving the Z axis at a constant speed based on the inclination of the plane assumes that the analysis area plane of the sample is approximated as one plane. In order to correct the height of the analysis surface with respect to the difficult complicated uneven surface, it is necessary to respond by subdividing the analysis region and planar approximation of each divided region.

In the case of performing a mapping analysis of a complex uneven surface by this driving method, (a) a plurality of divided mapping analyzes are performed in accordance with the inclination of the approximate plane in each divided area, and finally the results obtained from each mapping analysis are synthesized (or b) It is necessary to perform control to analyze the entire analysis area in one mapping operation.

In the control method by the division mapping (a), the sample stage is stopped and restarted repeatedly for each division, so that the analysis time becomes longer compared with the case where no division is performed. In addition, in the control method by one mapping in (b), it is necessary to change the driving speed of the Z axis one by one in accordance with the inclination of the approximate plane of the divided region each time the analysis position moves to a new divided region. In addition, the driving condition of the Z axis is given by the moving speed, not by the coordinates of the moving place. Therefore, a deviation occurs from the target coordinates due to the timing delay of the movement speed change, the error of the speed calculation, or the like. In addition, since the amount of this shift is accumulated each time the change of the drive speed is repeated, there is a risk that accurate correction becomes difficult.

5 is a graph for explaining a position error in the Z-axis direction generated by the control of (b). FIG. 5A shows a Z-axis correction value D, which is a control value in the Z-axis direction of the sample stage with respect to the movement in the X and Y directions with respect to the plane of the plane approximation. The Z axis of the sample stage is moved up and down at a constant speed in each divided plane as shown in the speed F shown in Fig. 5B. As the control by the constant speed, the control delay time T is generated in the switching of the respective analysis regions, and as shown by the solid line G in FIG. Offset occurs. Fig. 5 (d) shows the position error H in the Z axis direction, and the position error H is accumulated in accordance with the movement in the X and Y directions.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to control the height of the Z-axis with high precision so that the light condensing conditions of the X-ray spectrometer are always satisfied in the ray analysis or the mapping analysis of the uneven surface of the sample.

1 is a schematic block diagram of a configuration example to which a stage driving method of an electronic probe microanalyzer of the present invention is applied;

2 is a flowchart for explaining a schematic example of the stage driving method of the present invention;

3 is a graph for explaining a schematic example of the stage driving method of the present invention;

4 is a graph for comparing the error by the stage driving method of the present invention with the error by the conventional stage driving method;

5 is a graph for explaining a position error in the Z-axis direction generated by the conventional control.

<Description of the symbols for the main parts of the drawings>

1: electronic probe micro analyzer 2: computer

3: stage controller 4: driver

5: imaging means 6: monitor

11 filament 12 electron beam

13 condenser lens 14 objective lens

15 spectroscopic element 16 detection unit

17: Sample stage 21: Z axis correction function

22: Z-axis correction value forming unit 23: counter unit

24: interrupt processor 25: data memory

26: data processing unit

The stage driving method of the electronic probe microanalyzer of the present invention is to correct the Z-axis coordinate value in the height direction of the sample stage based on a predetermined condition in line analysis or mapping analysis. The Z-axis coordinate values are sequentially controlled based on the step-shaped Z-axis correction function determined by the function. In the stage driving method of the electronic probe microanalyzer, the condensing conditions of the X-ray spectrometer are determined at each analysis position in the analysis direction. A first step of including a Z-axis correction value (Zm) of the sample stage to be satisfied as a step-shaped Z-axis correction function and a next analysis direction based on the analysis position (m) of the Z-axis correction function and the current analysis direction; A second step of obtaining a Z-axis correction value (Zm) at the analysis position (m) of the sample, and the sample by the number of pulses (Nm) corresponding to the corresponding Z-axis correction value (Zm) And a fourth step of driving the z-axis of the stage and a fourth step of repeating the second and third steps by the total number of steps (M). Condensing of the X-ray spectrometer at each analysis position in the analysis direction The Z-axis correction value of the sample stage that satisfies the condition is provided as a step-shaped Z-axis correction function, and the Z-axis correction value at the analysis position in the next analysis direction is based on the Z-axis correction function and the analysis position in the current analysis direction. Drive the Z-axis of the sample stage with the calculated Z-axis correction value.

By using the step-shaped Z-axis correction function, the position control is sequentially performed in the Z-axis direction, thereby reducing the accumulated position error that occurs when the speed control is performed. To control.

The sample stage of the present invention can drive in each direction of the X, Y and Z axes, and when the sample is placed on the X and Y planes formed in the X and Y axes, the X and Y axes are driven. The analysis position on the sample surface is moved in the analysis direction in the line analysis or mapping analysis, and the light condensing condition of the X-ray spectrometer is satisfied by driving the Z axis.

The Z-axis correction function obtains the Z-axis correction value for correcting the sample stage in advance in order to satisfy the condensing conditions of the X-ray spectrometer at each analysis position according to the analysis direction for the sample to be measured. Is a function of. Therefore, by calculating the value of the Z-axis correction function at each analysis position, the Z-axis correction value for correcting the sample stage at the analysis position can be obtained. The Z-axis correction value is used to control the height direction of the sample stage. By doing so, the light condensing conditions of the X-ray spectrometer can be satisfied. Since the Z-axis correction value given as a step function is position data in the height direction for each analysis position, and is a control for instructing the height for a predetermined analysis position, the control in the Z-axis direction is sequentially controlled by position Position error due to control delay such as control can be reduced.

When the sample stage is driven by a stepping motor, a position pulse corresponding to the magnitude of the Z-axis correction value is supplied to the stepping motor to perform position correction in the height direction. The width of the analysis direction performed using the same Z-axis correction value is determined by the step width of the stepped portion of the correction function, and this step width counts the number of pulses supplied to the stepping motor in order to cause the movement in the analysis direction. It can be obtained by

Therefore, after correcting the position in the height direction with the Z-axis correction value, the number of pulses supplied to drive the X-axis and the Y-axis is counted, and the count value becomes a number corresponding to the step width of the stepped portion. Each time, the position correction in the height direction is performed with the Z axis correction value of the stepped portion, and the step width corresponding to the Z axis correction value is counted by the number of pulses driving the X and Y axes. By repeating this process, stage driving by a stepped Z-axis function can be performed.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings.

1 is a schematic block diagram of a configuration example to which the stage driving method of the electronic probe micro analyzer of the present invention is applied. In the electron probe microanalyzer 1 shown in FIG. 1, the electron beam 12 generated from the filament 11 is disposed on the sample stage 17 through the condenser lens 13 and the objective lens 14. S) is investigated. The X-rays emitted from the sample S are analyzed with an X-ray spectrometer including a spectroscopic element 15 for spectroscopic wavelength analysis and a detector 16 for detecting spectroscopic characteristic X-rays.

The sample stage 17 can move in the X, Y, and Z axis directions by the driver 4 receiving the control pulse from the stage controller 3. By driving the X and Y axes, the sample S is moved with respect to the electron beam 12 on the X and Y planes to perform line analysis or mapping analysis.

The stage controller 3 performs positioning in the X and Y axis directions and height adjustment in the Z axis directions by a control command from the computer 2. In observation of the sample S, the image reflected by the reflector 18 is picked up by an imaging device 5 such as a CCD camera and displayed on the monitor 6. Preliminary analysis and mapping analysis are performed by data processing the measurement signal obtained by the detector 16 with each function in the computer 2. The computer 2 is provided with functional means, such as the data memory 25 and the data processing part 26, and performs the data processing of the measurement signal and the display to the monitor 6. As shown in FIG.

Z-axis correction function means 21 for calculating the Z-axis correction function by inputting the Z-axis correction value representing the Z-axis coordinate value as a step function, in order for the computer 2 to perform the height correction in the Z-axis direction. From the axis correction function, the Z axis correction value forming unit 22 for forming the Z axis correction value and the pulse number corresponding to the step width, the counter unit 23 for counting the amount of movement in the analysis direction, and the Z axis correction value are obtained. 3) each function means such as an interrupt processing unit 24 for determining a timing to be sent to 3).

In addition, although each function is shown by block 21-26 in FIG. 1, each function of these can be implement | achieved by software and it does not necessarily need to provide the corresponding component part.

The Z-axis correction function is a step shape function of the Z-axis correction value for correcting the sample stage to satisfy the condensing conditions of the X-ray spectrometer at each analysis position according to the analysis direction of the sample to be measured. Usually, the electron probe microanalyzer is comprised so that the position used as a condensing condition of an X-ray spectrometer and the focal position on observation by an optical microscope may correspond. The observation image by an optical microscope can be acquired by the imaging device 5, and the focal position of the observation image can be calculated | required by the autofocus function which is not shown in figure. Therefore, the Z-axis coordinate value when the sample surface satisfies the condensing conditions of the X-ray spectrometer at a plurality of analysis positions in the analysis region by means of an unillustrated means of the electron probe microanalyzer 1 is the focal point of the observation with an optical microscope. Can be obtained from the location. In addition, a Z-axis coordinate value can be calculated | required from the observation image by an optical microscope, and can be obtained by other measuring means.

The Z-axis correction function means 21 inputs the obtained Z-axis coordinate values to obtain Z-axis coordinate values satisfying condensing conditions at each analysis position in the analysis area as Z-axis correction values, and calculates the distribution of the obtained Z-axis correction values. Obtain In addition, the change of the Z axis correction value with respect to the analysis direction of the line analysis or the mapping analysis is formed as a step Z-axis correction function.

Therefore, the Z-axis correction function becomes a different function depending on the analysis region of the line analysis or the mapping analysis or the line to be analyzed. In addition, the change width of Z-axis coordinate value can be set arbitrarily.

The Z-axis correction value forming unit 22 forms a parameter for causing correction control in the height direction of the sample stage 17 and outputs the parameter to the stage controller 3. The Z-axis correction value forming unit 22 outputs the parameter of the Z-axis correction value to the stage controller 3, and outputs the number of pulses corresponding to the step width of the Z-axis correction value to the interrupt processing unit 24.

The stage controller 3 supplies a pulse for controlling the stepping motor of the sample stage 17 to the driver 4. The movement in the X-axis direction and the movement distance in the Y-axis direction are determined by the number of pulses to be sent, and the analysis position in the analysis direction of line analysis or mapping analysis can be obtained by counting the number of pulses. In addition, the stage controller 3 drives the driver 4 based on the Z-axis correction value sent from the Z-axis correction value forming unit 22 to correct the height of the sample stage 17.

The counter 23 counts the pulse coefficients n in the X-axis and Y-axis directions output by the stage controller 3 to obtain an analysis position.

The interrupt processing unit 24 receives the pulse number N corresponding to the step width of the Z axis correction value from the Z axis correction value forming unit 22 and receives the pulse coefficient n counted by the counter 23 to receive the pulse number. (N) and the pulse coefficient n are compared. When the pulse coefficient n reaches the pulse number N, an interrupt signal is generated to perform height correction by the next Z-axis correction value.

In addition, the transmission unit between the computer 2 and the stage controller 3 can be performed using a communication cable or the like.

A schematic example of the stage driving method of the present invention will be described using the flowchart of FIG. 2 and the graph of FIG.

In the flowchart of Fig. 2, the Z-axis correction function means 21 inputs a Z-axis correction value obtained in advance to obtain a Z-axis coordinate value that satisfies the condensing condition as a Z-axis correction value, and the distribution of this Z-axis correction value. The change in the Z-axis correction value for the analysis direction of the line analysis or the mapping analysis is obtained from the step-shaped Z-axis correction function. Fig. 3A shows an example of a staircase Z-axis correction function, and is formed in a staircase shape that is the step width Wm from the Z-axis correction value Zm (step S1). The Z-axis correction value forming unit 22 adjusts the Z-axis correction value Zm (B in Fig. 3B) and the step width Wm of the Z-axis correction value Zm based on the Z-axis correction function. The corresponding pulse number Nm (FIG. 3C) is obtained (step S2).

The Z-axis correction value forming unit 22 sets the Z-axis correction value Zm shown in FIG. 3B and the number of pulses Nm shown in FIG. 3C in accordance with the following steps S3 to S10. Each time it counts, it outputs to the stage controller 3 in order.

First, the count value m for counting the steps of the stairs is set to 1 (step S3), and the number of pulses N1 corresponding to the step width W1 of the steps of the first steps is read, and the steps S5 to S8 are read. The Z axis is corrected by the first step. After the pulse coefficient n is initialized to 1 in step S5, the Z-axis correction value Z1 of the first step is output to the stage controller 3 in step S6, and the height correction by the Z-axis correction value Z1 is performed. After that, the pulses output by the stage controller 3 are sequentially counted in steps S7 and S8 until the pulse coefficient n exceeds the pulse number N1.

In step S7, when the pulse coefficient n reaches the pulse number N1, it can be detected that the analysis position in the analysis direction has reached the first step end. Then, after adding 1 to the count value m (step S9), step S8 is repeated in step S4 and Z-axis correction by the next step is performed.

In step S4, the process of step S9 is repeated until the count value m reaches the step number M, and thereby Z-axis correction by the step-shaped Z-axis correction function is performed.

In the normal program, when it is recognized that interrupt processing has been performed, driving to the target Z axis coordinate value currently set when the Z axis is not being driven is started.

4 is a graph for comparing the error by the stage driving method of the present invention and the error by the conventional stage driving method.

In FIG. 4A, the step Z-axis correction function A approximates the Z-axis coordinate value represented by D to the step shape. Therefore, as shown in FIG.4 (b), the error E by approximation generate | occur | produces. This error E does not accumulate because it is reset for each step. In addition, the magnitude | size of the error E in each step can be reduced by increasing the number of approximate steps, and can be made small compared with the error H by the conventional stage drive method shown in FIG. have.

According to the stage driving method of the present invention, since the Z axis coordinate value to be driven with respect to the current analysis position is given in advance, it is not necessary to calculate the driving speed every time as in the conventional driving method in actual driving of the Z axis, and the calculation time No control delay occurs by Moreover, even when a delay occurs in the timing of Z-axis control, since the parameter used for control is always provided as the Z-axis coordinate value of the next moving place, the deviation from the target position due to the repetition of the control is not expanded. This makes it possible to operate under the same correction conditions even if the moving speed of the analysis position is changed at the time of analysis, so there is no need to change the correction conditions in accordance with the moving speed of the sample stage at the time of analysis.

In the embodiment of the present invention, since the target Z axis coordinate value is changed by an interrupt processing routine, it is necessary to obtain the current target Z axis coordinate value by comparing the current position with the Z axis coordinate value sequentially. There is no risk of control delay by comparison operation.

In addition, since the Z-axis drive control is not newly performed in the state controlled by the Z-axis coordinate value within one step of the stairs, there is no sudden change of speed or stop immediately during Z-axis driving, which puts mechanical burden on the sample stage. There is no work.

As described above, according to the present invention, the height in the Z-axis direction can be controlled with high precision so as to always satisfy the condensing conditions of the X-ray spectrometer in the line analysis or the mapping analysis of the uneven surface of the sample.

Claims (1)

In the stage driving method of the electronic probe micro analyzer, A first step of providing a Z-axis correction value (Zm) of the sample stage satisfying condensing conditions of the X-ray spectrometer at each analysis position in the analysis direction as a step-shaped Z-axis correction function; A second step of obtaining a Z-axis correction value Zm at the analysis position m in the next analysis direction based on the Z-axis correction function and the analysis position m in the current analysis direction; A third step of driving the Z-axis of the sample stage by the number of pulses (Nm) corresponding to the obtained Z-axis correction value (Zm); And a fourth step of repeating the second and third steps by the total number of steps (M).