JPH05264483A - Method and device for measuring x-ray intensity for quantitative analysis in epma and the like - Google Patents

Abstract

PURPOSE:To measure X-ray intensity in a short time and accurately by continuously driving a spectral range of an X-ray spectroscope which can detect characteristic X ray of a specified element and then performing X-ray measurement for a certain amount of time within a certain drive interval. CONSTITUTION:An electron beam 2 is converged and applied onto a sample 5 by an objective lens 4 and a wavelength dissipation type X-ray spectroscope 7 detects a generated characteristic X ray. A spectroscope drive control device 12 controls a spectroscope drive motor 9 which drives a spectral crystal 8. On the other hand, an X-ray measurement device 11 controls detection operation of a detector 10. The device 12 is controlled by a computer 14 and at the same time sends a drive speed signal of the spectroscope 7 to the computer 14. Also, X-ray measurement value which is measured by the X-ray measurement device 11 is input to the computer 14. The obtained X-ray measurement value is stored in a storage device 13 and the values are displayed 15 graphically. Then, the obtained intensity distribution data are smoothed to obtain a secondary differential curve, thus obtaining a net characteristic X-ray intensity value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray intensity measuring method and a device therefor for quantitative analysis in EPMA, and more particularly to a method and a device therefor for measuring characteristic X-ray intensity accurately in a short time. Regarding

[0002]

2. Description of the Related Art Conventionally, in quantitative analysis using a wavelength dispersive X-ray spectrometer such as an electron probe microanalyzer (hereinafter referred to as EPMA), a characteristic X-ray of a target element is first measured for an unknown sample. The peak of the detection signal is detected before and after the position of the spectroscope where it can be detected, and then at the peak position and at the background position at a certain distance before and after that position, for the standard sample of known concentration and the unknown sample of unknown concentration. The X-ray measurement was performed for a certain period of time, the net X-ray intensity per unit time was calculated from the results, and the ratio (k-value) thereof was calculated and used as the first approximation of the quantitative analysis.

[0003]

However, depending on the element (particularly, the light element), the net X-ray intensity ratio obtained as described above does not always give an accurate value as the first approximation of the quantitative analysis. However, there is a problem that the peak position may be slightly shifted depending on the compounding state of the substance.

The present invention has been made in view of such a situation, and an object thereof is a method for accurately measuring a characteristic X-ray intensity for a quantitative analysis in EPMA or the like and an apparatus therefor. Is to provide.

[0005]

An X-ray intensity measuring method for quantitative analysis in EPMA or the like of the present invention which achieves the above-mentioned object is a characteristic X-ray intensity of an element designated from discrete X-ray intensity distribution data. In the method of measuring, the obtained intensity distribution data is smoothed, the second derivative curve of the smoothed intensity distribution curve is obtained, and the characteristic peak position of the characteristic X-ray and the spectral position at a certain distance before and after the theoretical peak position. If there is no maximum value of the second derivative value in the background position, the spectral position distant from the theoretical peak position by a certain distance is set as the background position, and the maximum value of the second derivative value is between the theoretical peak position and the spectral position distant by a certain distance. Is present, the minimum value position of the smoothed X-ray distribution curve corresponding to the maximum value is set as the background position, and smoothing is performed at the two calculated background positions. The two points on the intensity distribution curve connected by a straight line, by determining the area surrounded by the straight line and the smoothed intensity distribution curve is a method characterized by obtaining the characteristic X-ray intensity values of the net.

The apparatus of the present invention for carrying out the above method further comprises an X-ray spectroscope, continuously drives the spectroscopic range of the spectroscope capable of detecting the characteristic X-ray of a designated element, and
The spectroscope has a spectroscope drive control means for sending an X-ray measurement start signal at each predetermined constant drive interval of the spectroscope, and an X-ray measurement means for performing X-ray measurement for a predetermined time within the predetermined constant drive interval. Is set so that the X-ray measurement for the constant time is completed within the predetermined constant drive interval.

[0007]

In the method of the present invention and the apparatus for carrying out the method, the measurement time can be shortened by the absence of peak detection, and when there is a peak in the vicinity of the characteristic X-ray spectrum, it is simply a constant distance before and after the peak position. The background value can be more correctly and underestimated than when the position of is regarded as the background. further,
Even if the actual peak position is detected with a slight deviation from the theoretical position, the measured net X-ray intensity value is stable, and the accuracy of quantitative analysis of the element sensitive to the X-ray peak position is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The EPMA of the present invention will now be described with reference to the drawings.
Examples of the X-ray intensity measurement method for quantitative analysis and the apparatus therefor will be described. FIG. 1 is a diagram showing a configuration of an EPMA according to the present invention, in which an electron beam 2 emitted from an electron gun 1 is convergently irradiated onto a sample 5 placed on a stage 6 by a converging lens 3 and an objective lens 4. It The characteristic X-ray generated from the sample 5 is detected by the wavelength dispersive X-ray spectroscope 7. The wavelength dispersive X-ray spectroscope 7 includes a dispersive crystal 8, a spectroscope drive motor 9, and a detector 10. The spectroscope drive motor 9 that drives the dispersive crystal 8 is controlled by a spectroscope drive controller 12. Be seen. Hereinafter, for simplicity of explanation, it is assumed that the drive motor 9 is a pulse motor, and the spectroscope drive control device 12 drives the pulse motor 9 by generating a drive pulse. On the other hand, the detection operation of the detector 10 is controlled by the X-ray measuring device 11, and the X-ray measuring device 11 is controlled by the spectroscope drive control device 12 at every constant number of drive pulses. One pulse signal is input. The spectroscope drive controller 12 is controlled by the computer 14 and sends a drive speed (pulse generation time interval) signal of the spectroscope 7 to the computer 14. Further, the X-ray measurement value measured by the X-ray measurement device 11 is also input to the computer 14. The obtained X-ray measurement values are stored in the storage device 13, and those values can be graphed and displayed on the display output device 15.

When detecting a spectrum by moving the X-ray spectroscope 7 once, the number of data points collected at equal intervals in the moving region is N points, and the detector 10 for each data point is detected.
Is a constant X-ray collection time (dwell time) by T, and n is the number of pulse steps of the motor 9 that moves the spectroscope 7 while collecting data for one point. The timing chart (1 cycle) is as shown in FIG. In order to collect N points of data, the cycle of FIG. 2 is repeated N times. In addition,
In order to complete the data collection at one point during the movement of the spectroscope 7 for one cycle, the driving speed v measured by the number of pulses of the spectroscope 7 needs to be n / T or less. A dummy time t occurs when the spectroscope 7 moves without performing (X-ray measurement). The dummy time t is, as shown in FIG. 2, a time g required for turning on the gate of the detector 10 from the n-step driving end pulse of the previous cycle, a time m for taking the measured X-ray data into the memory from turning off the gate of the detector 10,
Also, the next n from the acquisition of the measured X-ray data into the memory
It is given by the sum of the time u until the step drive end pulse arrives, but any of these times can be shortened. Therefore, the dummy time t is kept small and X
It is possible to make it practically negligible compared to the line measurement time T (the dummy time is set large in FIG. 2 for the sake of clarity).

By doing so, the total data acquisition time can be made shorter than in the conventional case in which the spectroscope stops after moving n steps and measures X-rays. Further, if the dummy time occupied in the entire data acquisition time is reduced, the time during which the X-ray is not measured during the driving of the spectroscope 7 is reduced accordingly, and the probability of escaping the peak of the X-ray peak profile is reduced during this time. Therefore, more accurate spectrum data collection becomes possible. Further, the X-ray acquisition time T is kept constant even when the drive pulses are not evenly spaced, for example, when the movement control is such that the speed gradually increases at the rising, is constant at the intermediate position, and gradually decreases at the stop. Then, accurate detection can be performed regardless of speed changes.

In the above description, the spectroscope driving means is a pulse motor, but the spectroscopic driving means is not limited to this, and may be a microstepping motor that drives in very small steps, or a DC motor that does not depend on a pulse current. However, in the case of a DC motor, it is necessary to perform position detection by means such as an encoder in order to give an X-ray measurement start signal at constant drive intervals.

Next, the peak profile of the X-ray spectrum is collected by using the above X-ray intensity measuring apparatus,
The method for obtaining the characteristic X-ray intensity for quantitative analysis is shown below. First, from the characteristic X-ray wavelength of the designated element,
A spectroscope position where a ray can be detected is obtained, data before and after the spectroscope position are collected, and the obtained X-ray intensities are I ₁ , I ₂ ,
..., I _N. When these intensities are plotted on the graph, it becomes as shown by the mark X in FIG. next,
These data are smoothed by a method such as approximation to a higher-order polynomial by the moving least square method. The obtained curve A is shown in FIG. Next, this curve A is secondarily differentiated. This second-order differentiated curve B is shown in FIG. Next, the back of the position of a fixed front and rear distance L _B− , L _{B +} (L _B− = L _{B +} ) from the theoretical peak position c of the characteristic X-ray calculated from the characteristic X-ray wavelength in consideration of the spectroscopic state, the combination state, etc. The spectroscope position that is considered to be the ground is obtained, and it is determined whether or not there is a positive second-order differential value between the theoretical peak position c and the positions that are considered to be the background before and after it. If it does not exist (+ direction), the position d that is considered to be the above background is regarded as the background position. If it exists (in the negative direction), the position corresponding to the positive maximum position is the position of the minimum value of the original smoothed X-ray intensity distribution curve A, so that point e is set as the true packed ground position. ..
A background straight line F is created by connecting the points on the smoothed X-ray intensity distribution curve A at the background positions d and e thus determined before and after the theoretical peak with a straight line. The area of the region surrounded by the peak profile A and the background straight line F is obtained and used as the net X-ray intensity value. The above is the method of obtaining the X-ray intensity value of an unknown sample. However, in the case of comparison with a standard sample, the background positions d and e obtained above are adopted, and a background straight line is drawn in the same manner. The area surrounded by the peak profile and the background straight line is taken as the net X-ray intensity value of the standard sample.

When the net X-ray intensity value of the characteristic X-ray is obtained in this manner, the measurement time can be shortened by the amount that peak detection is not performed, as compared with the conventional method, and as shown in FIG. When there is a peak in the vicinity of the characteristic X-ray spectrum, the background value can be estimated more correctly and smaller than when the position at a certain distance in front and behind the peak position is simply regarded as the background. further,
Even if the actual peak position is detected with a slight deviation from the theoretical position, the measured net X-ray intensity value is stable, and the accuracy of quantitative analysis of the element sensitive to the X-ray peak position is improved.

Although the X-ray intensity measuring method and apparatus of the present invention have been described based on the embodiments, the present invention is not limited to these embodiments and various modifications can be made.

[0015]

As is apparent from the above description, according to the X-ray intensity measuring method for quantitative analysis in EPMA and the like and the apparatus therefor of the present invention, the measuring time can be shortened by the absence of peak detection. When there is a peak in the vicinity of the characteristic X-ray spectrum, the background value can be estimated more correctly and smaller than when the position at a certain distance in front and behind the peak position is simply regarded as the background. Further, even if the actual peak position is detected with a slight deviation from the theoretical position, the measured net X-ray intensity value is stable, and the accuracy of quantitative analysis of the element sensitive to the X-ray peak position is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of an EPMA according to the present invention.

FIG. 2 is a diagram showing an example of a timing chart for collecting one point of data by the device of the present invention.

FIG. 3 is a diagram for explaining an X-ray intensity measuring method based on the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... Electron beam 3 ... Converging lens 4 ... Objective lens 5 ... Sample 6 ... Stage 7 ... Wavelength dispersive X-ray spectroscope 8 ... Spectroscopic crystal 9 ... Spectrometer drive motor 10 ... Detector 11 ... X-ray measurement Device 12 ... Spectrometer drive control device 13 ... Storage device 14 ... Computer 15 ... Display output device

Claims (2)

[Claims] 1. A method for measuring the characteristic X-ray intensity of an element designated from discrete X-ray intensity distribution data, wherein the obtained intensity distribution data is smoothed, and a second derivative of the smoothed intensity distribution curve is obtained. If there is no maximum value of the second derivative between the theoretical peak position of the characteristic X-ray and the spectral position separated by a certain distance before and after the curve, the spectral position separated by a certain distance from the theoretical peak position is set as the background position. If there is a local maximum of the second derivative between the theoretical peak position and the spectral position separated from the theoretical peak position by a certain distance, the local minimum position of the smoothed X-ray distribution curve corresponding to the local maximum is set to the background position. Then, connect the two points on the smoothed intensity distribution curve at the two obtained background positions with a straight line, and find the area enclosed by this straight line and the smoothed intensity distribution curve. An X-ray intensity measuring method for quantitative analysis in EPMA or the like, characterized in that a net characteristic X-ray intensity value is obtained by 2. An X-ray spectroscope is provided, which continuously drives a spectroscopic range of the spectroscope in which characteristic X-rays of a designated element can be detected, and X is measured at predetermined constant drive intervals of the spectroscope. A spectroscope drive control means for sending a line measurement start signal and an X-ray measurement means for performing X-ray measurement for a fixed time within the predetermined constant drive interval are provided, and the drive speed of the spectroscope is within the predetermined constant drive interval. The apparatus for performing the X-ray intensity measurement method according to claim 1, wherein the X-ray measurement for a certain period of time is set to be completed.