JP2004069407A - X-ray analyzer - Google Patents

Abstract

An object of the present invention is to precisely control a height in a Z-axis direction so that a distance between a sample surface and an X-ray detector or a spectroscope is always constant, and perform accurate analysis in a short time.
In a line analysis and a mapping analysis, a Z-axis coordinate in a height direction of a sample stage is corrected based on a predetermined condition, and a Z-axis coordinate to be driven during the analysis is changed to a polygonal Z-axis. A Z-axis coordinate value is determined sequentially by a correction function, and the Z-axis coordinate value is sequentially controlled based on the polygonal Z-axis correction function. At each analysis position in the analysis direction, a Z-axis correction value of the sample stage satisfying the X-ray detection condition is provided as a polygonal Z-axis correction function, and based on the Z-axis correction function and the analysis position in the current analysis direction, The Z-axis correction value at the analysis position in the next analysis direction is obtained, and the Z-axis of the sample stage is driven to the obtained Z-axis correction value. Further, the stage driving speed in the analysis direction is changed so that the driving speed of the Z-axis becomes a safe constant speed.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray analyzer, and more particularly, to driving a sample stage included in the X-ray analyzer.
[0002]
[Prior art]
In the energy dispersive X-ray fluorescence spectrometer, the distance between the sample surface and the X-ray detector or the spectrometer is set to be constant as a condition for detecting the X-ray fluorescence emitted from the sample by primary X-ray irradiation. Is required. In an electron probe microanalyzer (EPMA) using a wavelength dispersive spectroscope, the conditions for focusing the sample, the spectral crystal, and the detector are as follows. It is required that the X-ray spectrometer be accurately arranged on the circumference of the Rowland circle.
[0003]
Usually, these X-ray detection conditions are performed by adjusting the height of the sample surface.
[0004]
In X-ray analysis using a fluorescent X-ray analyzer, electron probe microanalyzer, etc., one-dimensional or two-dimensional X-ray signal is detected by detecting the X-ray signal each time while changing the analysis position on the sample surface one by one. There are line analysis and mapping analysis to obtain distribution.
[0005]
In the line analysis and the mapping analysis, a sample is moved at a constant speed on the X and Y planes, and X-ray signals are measured at regular intervals during this movement. When performing line analysis or mapping analysis on a sample surface having irregularities, 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 accurate measurement, it is necessary to always control the height direction of the sample stage so that the distance between the sample surface and the X-ray detector or the spectrometer is constant at each analysis position.
[0006]
Conventionally, as a method of controlling the height direction of a sample stage, an actual measurement value or an approximate value of the Z-axis coordinate value of the sample stage when the height of the sample surface satisfies the X-ray detection condition is obtained in advance over the entire analysis area. A method of controlling the Z-axis coordinate of the sample stage based on the obtained Z-axis coordinate value is known.
[0007]
Conventionally, as a driving method for controlling the Z-axis coordinate of the sample stage, the entire analysis area is approximated by one plane, and the Z-axis is moved at a constant speed with respect to the movement at a constant speed in the X and Y-axis directions. There is known a driving method that follows the inclination of a plane.
[0008]
[Problems to be solved by the invention]
The driving method of approximating the entire analysis region in one plane and moving the Z axis at a constant speed based on the inclination of the plane is based on the assumption that the analysis region surface of the sample is approximated as one plane. In order to correct the height of the analysis surface with respect to a complicated uneven surface that is difficult to approximate, it is necessary to subdivide the analysis region and approximate each of the divided regions on a plane.
[0009]
When performing a mapping analysis of a complicated uneven surface by this driving method, (a) a mapping analysis is performed a plurality of times in accordance with the inclination of the approximate plane in each of the divided regions, and a result obtained in each mapping analysis is obtained. It is necessary to perform the final synthesis or (b) control to analyze the entire analysis area by one mapping operation.
[0010]
In the control method based on the division mapping of (a), since the sample stage is repeatedly stopped and restarted for each division, there is a problem that the analysis time is longer than in the case where division is not performed. Further, in the control method based on one-time mapping in (b), every time the analysis position moves to a new divided region, it is necessary to change the driving speed of the Z-axis one by one according to the inclination of the approximate plane of the divided region. Further, since the driving condition of the Z-axis is given not by the coordinates of the movement destination but by the movement speed, a deviation from the target coordinates occurs due to a delay in change timing of the movement speed, an error in speed calculation, or the like. Further, since this shift amount is accumulated each time the drive speed is changed, accurate correction may be difficult.
[0011]
FIG. 4 is a graph for explaining a position error in the Z-axis direction generated by the control (b). FIG. 4A shows a Z-axis coordinate value A 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 sample approximated. The Z axis of the sample stage is moved up and down at a constant speed, such as a speed B shown in FIG. In the control at a constant speed, a control delay time T occurs at the time of switching between the analysis regions, and a deviation from a target value A indicated by a broken line occurs as shown by a solid line C in FIG. FIG. 4D shows the position error D in the Z-axis direction, and the position error D is accumulated with the movement in the X and Y directions.
[0012]
In addition, there is a limit to the driving speed of the Z-axis, and when moving at a constant speed in the directions of the X and Y axes, the Z-axis is corrected to exceed the allowable speed for a portion having extremely unevenness (step). Therefore, the stage may be damaged. Conversely, if the stage driving speed in the analysis direction is reduced to cope with a large change in the Z-axis direction, there is a problem that the analysis time becomes longer.
[0013]
Therefore, the present invention solves the above-mentioned conventional problems, and in the line analysis or mapping analysis of a sample surface having irregularities, the Z-axis is set so that the distance between the sample surface and the X-ray detector or the spectrometer is always constant. An object of the present invention is to precisely control a direction height and to perform a highly accurate analysis in a short time.
[0014]
[Means for Solving the Problems]
The X-ray analyzer of the present invention corrects the Z-axis coordinate in the height direction of the sample stage based on a predetermined condition, and determines the Z-axis coordinate to be driven during the analysis by a polygonal function, The Z-axis coordinate values are sequentially controlled based on the polygonal Z-axis correction function, and the distance between the sample surface and the X-ray detector or X-ray spectrometer is kept constant at each analysis position in the analysis direction. A Z-axis correction value of the sample stage is provided as a polygonal Z-axis correction function, and a Z-axis correction value at an analysis position in the next analysis direction is determined based on the Z-axis correction function and the analysis position in the current analysis direction. The Z axis of the sample stage is driven to the obtained Z axis correction value.
[0015]
At this time, the X-axis and / or Y-axis stage drive speed in the analysis direction is changed so that the Z-axis drive speed becomes a safe constant speed.
[0016]
The X-ray analyzer of the present invention uses a polygonal Z-axis correction function to perform sequential position control in the Z-axis direction, and further to perform speed control by setting the Z-axis drive speed to a constant speed. Is reduced, and the height in the Z-axis direction is accurately controlled.
[0017]
The sample stage of the present invention can drive in each of the X-axis, Y-axis, and Z-axis directions. When the sample is placed on an X-Y plane formed by the X-axis and the Y-axis, The analysis position on the sample surface is moved in the analysis direction in the line analysis or mapping analysis by driving the axis and the Y axis, and the X-ray detection condition is satisfied by driving the Z axis.
[0018]
For the Z-axis correction function, a Z-axis correction value for correcting the sample stage in order to satisfy the X-ray detection condition is determined in advance at each analysis position along the analysis direction with respect to the sample to be measured. Is a polygonal function. Therefore, by obtaining the value of the Z-axis correction function at each analysis position, a Z-axis correction value for correcting the sample stage at that analysis position can be obtained. The X-ray detection condition can be satisfied by controlling the height direction. The Z-axis correction value given by the polygonal function is position data in the height direction for each analysis position, and is a control for instructing the height itself for a predetermined analysis position. Position control is performed, and a position error due to a control delay such as speed control can be reduced.
[0019]
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 in the analysis direction performed using the same Z-axis correction value is determined by the step width of the polygonal line portion of the correction function, and the step width determines the number of pulses supplied to the stepping motor for performing the movement in the analysis direction. It can be obtained by counting.
[0020]
In a predetermined area, the time required for the Z-axis correction can be obtained from the Z-axis correction amount, and the stage drive speed in the analysis direction can be obtained from the time and the step width.
[0021]
Therefore, the position correction in the height direction is performed at a constant speed based on the Z-axis correction value, and at the same time, the X-axis and Y-axis drive speeds are changed according to the obtained stage drive speed. In the driving of the X, Y and Z axes, the number of pulses supplied for driving the X and Y axes is counted for the Z axis, and each time the counted value becomes a number corresponding to the step width of the polygonal line portion. Next, position correction in the height direction is performed using the Z-axis correction value of the polygonal line portion. On the other hand, for the X and Y axes, the drive speed of the X and Y axes is changed, and the step width corresponding to the Z axis correction value is counted by the number of pulses for driving the X and Y axes. By repeating this process, the stage can be driven by the polygonal Z-axis function.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic block diagram of a configuration example in which the X-ray analyzer of the present invention is applied to a fluorescent X-ray analyzer. In the X-ray fluorescence analyzer 1 shown in FIG. 1, primary X-rays generated from the X-ray source 11 are irradiated on a sample S placed on a sample stage 14, and X-rays emitted from the sample S It is analyzed by a line detector (energy dispersive spectrometer) 12.
[0023]
The sample stage 14 can be moved in the X, Y, and Z axis directions by the driver 4 that has received a control pulse from the stage controller 3. The sample S is moved on the X, Y plane with respect to the primary X-ray by driving the X-axis and the Y-axis, and the line analysis or the mapping analysis is performed.
[0024]
The stage controller 3 performs positioning in the X and Y axis directions and adjusts the height in the Z axis direction according to control commands from the control computer 2. For observation of the sample S, an image is taken by an image pickup means 13 such as a CCD camera and displayed on the monitor 5. The line analysis and the mapping analysis are performed by subjecting the measurement signal obtained by the X-ray detector 12 to data processing by each function in the control computer 2. The control computer 2 includes functional units such as a data memory 25 and a data processing unit 26, and performs data processing of a measurement signal and display on the monitor 5.
[0025]
In order to perform the height correction in the Z-axis direction, the control computer 2 inputs a Z-axis correction value representing the Z-axis coordinate value by a polygonal function to obtain a Z-axis correction function, A Z-axis correction value forming unit 22 that calculates the number of pulses corresponding to the Z-axis correction value and the step width from the axis correction function and a driving speed in the analysis direction, a counter 23 that counts the amount of movement in the analysis direction, and a Z-axis correction value and Each functional unit such as an interrupt processing unit 24 that determines the timing of sending the drive speed in the analysis direction to the stage controller 3 is provided.
[0026]
In FIG. 1, each function is indicated by blocks 21 to 26, but each of these functions can be executed by software and does not necessarily have a corresponding component.
[0027]
The Z-axis correction function calculates a Z-axis correction value for correcting the sample stage in order to keep the distance between the analysis position and the X-ray detector constant at each analysis position along the analysis direction of the sample to be measured. And Normally, an X-ray fluorescence analyzer is configured such that an analysis position at a certain distance from an X-ray detector (or X-ray spectroscope) coincides with a focal position of an image observed by an imaging unit such as a CCD camera. I have. The observation image can be obtained by the imaging unit 13, and the focal position of the observation image can be obtained by an autofocus function (not shown). Therefore, the X-ray fluorescence analyzer 1 calculates the Z-axis coordinate value when the sample surface is at a certain distance from the X-ray detector (or X-ray spectrometer) at a plurality of analysis positions in the analysis area. From the focal position. FIG. 1 does not show a configuration for obtaining the Z-axis coordinate value. In addition, the Z-axis coordinate value can be obtained by other measuring means in addition to the above-described calculation from the observation image.
[0028]
The Z-axis correction function means 21 inputs the obtained Z-axis coordinate values, obtains the Z-axis coordinate values satisfying the X-ray detection conditions at each analysis position in the analysis area as the Z-axis correction values, and obtains the obtained Z-axis correction values. Find the distribution of Further, a change in the Z-axis correction value in the analysis direction of the line analysis or the mapping analysis is formed as a polygonal Z-axis correction function. Therefore, the Z-axis correction function differs depending on the analysis area of the line analysis or the mapping analysis or the line to be analyzed. This analysis line is not limited to a straight line, but may be an arbitrary curve.
[0029]
The Z-axis correction value forming unit 22 is a part that calculates a parameter for performing the correction control of the sample stage 14 in the height direction and a driving speed in the analysis direction, and outputs the parameter to the stage controller 3. The Z-axis correction value forming unit 22 outputs the parameter 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.
[0030]
The stage controller 3 supplies a pulse for controlling the stepping motor of the sample stage 14 to the driver 4. The moving distance in the X-axis direction and the moving distance in the Y-axis direction are determined by the number of transmitted pulses, and by counting the number of pulses, the analysis position in the analysis direction of the line analysis or the mapping analysis can be obtained. 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 and the driving speed in the analysis direction, and corrects the height of the sample stage 14 and the driving speed in the analysis direction. Perform control.
[0031]
The counter 23 counts the number n of pulses output from the stage controller 3 in the X-axis and Y-axis directions to determine an analysis position.
[0032]
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, inputs the pulse count n counted by the counter 23, and outputs the pulse number N and the pulse count n. Is compared. When the pulse count n reaches the pulse number N, an interrupt signal is generated, and the height is corrected by the next Z-axis correction value.
[0033]
With reference to the flowchart of FIG. 2 and the graph of FIG. 3, a schematic example of stage driving of the X-ray analyzer of the present invention will be described.
In the flowchart of FIG. 2, the Z-axis correction function means 21 inputs a Z-axis correction value obtained in advance, obtains a Z-axis coordinate value satisfying the X-ray detection condition as a Z-axis correction value, , The change of the Z-axis correction value with respect to the analysis direction of the line analysis or the mapping analysis is obtained as a linear Z-axis correction function. FIG. 3A shows an example of a polygonal Z-axis correction function, which is formed in a polygonal shape having a step width Wm with a Z-axis correction value ΔZm (step S1). The Z-axis correction value forming unit 22 calculates the Z-axis correction value ΔZm (FIG. 3B) based on the Z-axis correction function and the number of pulses Nm corresponding to the step width Wm of the Z-axis correction value ΔZm. The stage drive speed Vm in the analysis direction is determined such that the drive speed of the Z axis becomes a predetermined constant value.
[0034]
For example, when the amount of movement in the Z-axis direction per step is dz, the number of pulses Nm required to correct the Z-axis correction value ΔZm is represented by (ΔZm / dz). When each pulse is output at a predetermined time interval dt, the time required to correct the Z-axis correction value ΔZm can be represented by (Nm × dt) obtained by multiplying the number of pulses Nm by the time interval dt. . The stage drive speed Vm (the drive speed of the X and Y axes) can be expressed as Wm / (Nm × dt), assuming that the step width Wm moves within this time (Nm × dt) (step S2).
[0035]
The Z-axis correction value forming unit 22 changes the Z-axis correction value ΔZm shown in FIG. 3B and the stage drive speed Vm in the analysis direction shown in FIG. 3C according to the following steps S3 to S11. Each time the number Nm is counted, it is sequentially output to the stage controller 3.
[0036]
First, the count value m for counting an area is set to 1 (step S3), and the number of pulses N1 (= (ΔZ1 / dz)) corresponding to the step width W1 of the first area in the polygonal Z-axis correction function. ) Is read, and the Z-axis is corrected in the first region according to steps S5 to S9. Note that the area represented by the polygonal Z-axis correction function is an area represented by a straight line on the X-axis direction, the Y-axis direction, or the X-Y plane, or an arbitrary curve on the X-Y plane. The area may be represented by:
[0037]
After the pulse count n is initialized to 1 in step S5, the Z-axis correction value ΔZ1 set in the first area is output to the stage controller 3 in step S6, and one step of the Z-axis correction value ΔZ1 is selected. The minute height dz is corrected. By performing correction for all the pulses of the number of pulses Nm, all the Z-axis correction values ΔZ1 are corrected.
[0038]
In step S7, the stage drive speed Vm in the analysis direction is output to the stage controller 3 to perform speed control. The stage drive speed Vm in the analysis direction is represented by Vm = (Wm / ((ΔZm / dt) · dt)) = (Wm / ΔZm). Therefore, when the Z-axis correction value ΔZm is large with respect to the step width Wm of the area, the stage driving speed Vm is slow. Conversely, when the Z-axis correction value ΔZm is small with respect to the step width Wm of the area, the stage drive is performed. The speed Vm increases. In a region where there is no Z-axis correction or a region where Z-axis correction is small, the stage drive speed Vm is set to the maximum speed allowed by the sample stage.
[0039]
Thereafter, in steps S8 and S9, the pulses output by the stage controller 3 are sequentially counted until the pulse count n exceeds the pulse number N1.
[0040]
In step S8, when the pulse count n has reached the pulse number N1, it can be detected that the analysis position in the analysis direction has reached the end of the first region. Thereby, the correction in the Z-axis direction in the first region of the Z-axis correction function represented by the polygonal line is completed.
[0041]
Then, after adding 1 to the count value m (step S10), steps S4 to S9 are repeated to perform the Z-axis correction in the next area of the Z-axis correction function represented by the broken line.
[0042]
The process from step S4 to step S10 is repeated until the count value m reaches the region M, thereby performing the Z-axis correction using the polygonal Z-axis correction function.
[0043]
In the above-described steps, an example is shown in which the region is sequentially moved from one end to the other end of the area defined by the polygonal Z-axis correction function. However, the starting point and the ending point of the movement are not limited to the ends, but may be any positions. You can also. Also, the area to be moved is not limited to the entire area, but may be an arbitrarily determined area. The arbitrarily selected area may be moved in an arbitrarily determined order. In addition, the polygonal Z-axis correction function can be not only linear but also planar in the X and Y planes, and can perform line analysis and mapping analysis.
[0044]
In a normal program, when it is recognized that the interrupt processing has been performed, the driving to the currently set target Z-axis coordinate value is started when the Z-axis is not being driven.
[0045]
According to the X-ray analyzer of the present invention, the distance between the analysis position and the X-ray detector (spectrometer) can be controlled to be always kept constant, and the Z-axis driving speed is reduced by the unevenness of the sample surface. Since the driving speed in the analysis direction can be changed so as to always maintain a safe constant speed, deviation due to Z-axis control timing delay can be minimized, and analysis can be performed in a shorter time than before. can do.
[0046]
In the embodiment of the present invention, since the change of the target Z-axis coordinate value is performed in the interrupt processing routine, it is necessary to obtain the current target Z-axis coordinate value by sequentially comparing the current position with the Z-axis coordinate value. Therefore, there is no risk of control delay due to the comparison operation.
[0047]
Further, since the driving speed of the Z-axis is always controlled to a safe constant speed, abruptly changing the Z-axis side speed due to unevenness of the sample surface does not impose a mechanical load on the sample stage.
[0048]
In the description of the above embodiment, the X-ray fluorescence analyzer is described as an example, but the present invention can be similarly applied to an electron probe microanalyzer.
[0049]
【The invention's effect】
As described above, according to the present invention, in line analysis or mapping analysis of a sample surface having irregularities, the sample height is set so that the distance between the sample surface and the X-ray detector or X-ray spectrometer is always kept constant. Can be accurately controlled.
[0050]
In addition, since the driving speed in the analysis direction can be changed so that the Z-axis driving speed always becomes a safe constant speed due to the unevenness of the sample surface, the analysis can be performed in a shorter time than before.
[0051]
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a configuration example in which an X-ray analyzer of the present invention is applied to a fluorescent X-ray analyzer.
FIG. 2 is a flowchart illustrating a schematic example of stage driving of the X-ray analyzer according to the present invention.
FIG. 3 is a graph for explaining a schematic example of stage driving of the X-ray analyzer of the present invention.
FIG. 4 is a graph for explaining a position error in the Z-axis direction generated by conventional control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... X-ray fluorescence analyzer, 2 ... Control computer, 3 ... Stage controller, 4 ... Driver, 5 ... Monitor, 6 ... Monitor, 11 ... X-ray source, 12 ... X-ray detector, 13 ... Imaging means, 14 ... Sample stage, 21: Z-axis correction function, 22: Z-axis correction value forming unit, 23: counter unit, 24: interrupt processing unit, 25: data memory, 26: data processing unit.

Claims (2)

At each analysis position in the analysis direction, a Z-axis correction value of the sample stage for keeping the distance between the analysis position and the X-ray detector or X-ray spectrometer constant is provided as a linear Z-axis correction function, and the Z-axis correction is performed. X-axis correction value at the analysis position in the next analysis direction is obtained based on the function and the analysis position in the current analysis direction, and the Z-axis of the sample stage is driven by the obtained Z-axis correction value. Line analyzer. In each region where the Z-axis correction value of the Z-axis correction function changes linearly, based on the width on the X and Y planes and the Z-axis correction amount in the region, the X-axis and / or Alternatively, the driving speed of the Y axis is set for each region,
2. The X-ray analyzer according to claim 1, wherein the driving speed of the Z-axis is always set to a constant speed in the entire region of the Z-axis correction function.

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