JP2692538B2 - Background correction method in X-ray spectroscopic analysis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a background correction method for content color mapping analysis in X-ray spectroscopy.

[0002]

2. Description of the Related Art In the elemental qualitative and quantitative analysis of a uniform sample, wavelength scanning is performed by an X-ray spectroscope, so that the characteristic X
Background correction is easy because the data of the intensity distribution of the background can be obtained together with the peak profile of the line.However, in the case of area analysis to examine the concentration distribution of the target element on the sample surface, one for each pixel point on the sample surface. Since it is practically impossible to perform wavelength scanning, X-ray intensity data at several fixed wavelengths are obtained. In this case, background correction is conventionally performed by the following method.

One of them is to measure the X-ray intensity at the characteristic X-ray wavelength of the target element at each point on the sample surface and subtract it from the above-mentioned measured intensity with a predetermined fixed value as the background. However, since the background intensity is not constant over the entire sample surface, accurate background correction cannot be performed.

The second is to measure the X-ray intensity of each pixel point on the sample surface for a wavelength deviated from the characteristic X-ray wavelength of the target element, and use this as the background to measure the characteristic X of the corresponding point.
It is subtracted from the measured value of the line strength. Although this method can deal with the background unevenness at each point on the sample surface, the background is a function of wavelength and is not a constant. Elemental characteristics X
Since the background is stronger than the X-ray intensity at the line wavelength position, the background cannot be corrected accurately.

[0005]

SUMMARY OF THE INVENTION The present invention provides a background correction method capable of performing accurate background correction at any point on the sample surface in X-ray spectroscopic analysis performed at a fixed wavelength such as surface analysis of the sample surface. It is the one we are trying to provide.

[0006]

The characteristic X-ray peak profile data of the target element is obtained by performing wavelength scanning, and the background intensity at the wavelength position of the characteristic X-ray is obtained from this data. The ratio of the X-ray intensity at another wavelength λb near the bottom of the peak profile is calculated, and the X-ray intensity at the characteristic X-ray wavelength and the wavelength λb is measured during actual analysis. The ratio was multiplied to obtain the background intensity at the characteristic X-ray wavelength of the target element, which was subtracted from the X-ray intensity at the characteristic X-ray wavelength.

[0007]

1A and 1B are graphs of X-ray intensity when wavelength scanning is performed by an X-ray spectrometer in a certain wavelength range before and after including the characteristic X-ray wavelength λp of the target element at two points on the sample surface. That is, the measured profile of the characteristic X-ray peak of the target element is shown. In these graphs, the one indicated by the dotted line shows the background intensity below the peak profile of the characteristic X-ray. This dotted line is a curve that monotonously connects the two tails of the peak profile, and can be drawn visually or by a method of calculating an empirical formula of the background from measured values at several wavelength points. In FIG. 1, the true characteristic X-ray intensity of the target element is on the perpendicular line standing from the wavelength λp,
It is the portion P above the intersection of the background with the dotted line, and the background intensity at λp is Bp.
The wavelength λb slightly apart from λp is a point near the bottom of the peak of the characteristic X-ray of the target element, and the X-ray intensity Bg here is the background intensity at that wavelength. If the value of Bp / Bg is obtained from A and B in FIG.
By measuring the X-ray intensity at two wavelengths of λp and λb and multiplying the measured value at λb by Bp / Bg, the correct background intensity at the characteristic X-ray wavelength λp of the target element can be obtained.

[0008]

FIG. 2 is a flow chart of a mapping operation of an embodiment in which the present invention is applied to color mapping in which the concentration distribution of a certain element on the sample surface is colorized and displayed. First, wavelength scanning is performed at multiple points on the sample surface, and
Profile data of the characteristic X-ray intensity of the target element as shown in (1) is collected (a). Next, for each point, the ratio Bp / B
g is obtained, and the value of the ratio at each point is averaged to obtain the coefficient α (b). Next, the wavelength of the X-ray spectroscope is set to λp, the sample surface is scanned, X-ray intensity data is collected for each pixel point, and the data is stored in the memory together with the coordinate data of that point (C). Next, the wavelength of the X-ray spectroscope is set to λb, the sample surface is scanned again, and X-ray intensity data and coordinate data are stored in the memory for each pixel point (d). Next, each data obtained in step (d) is multiplied by the coefficient α obtained in step (b), and the value is calculated at the characteristic X-ray wavelength of the target element obtained in step (c). The X-ray intensity is subtracted from the data for each same address (e), and finally the result is converted to color data on a color scale and displayed as a color map on the display surface (f).

In the above-mentioned embodiment, one X-ray spectroscope has a wavelength λ
Although the sample surface is scanned twice with p and λb, when an apparatus in which a plurality of X-ray spectroscopes are arranged on the side of the sample is used, the X-ray intensity at the wavelengths λp and λb can be changed by one scan. You can get the data. The present invention can be applied to both an X-ray spectrometer and a wavelength dispersion type or energy dispersion type.

[0010]

In the X-ray spectrometer, the background is a function of wavelength, and even if the background is measured in the vicinity of the characteristic X-ray wavelength, it does not show the background at the characteristic X-ray wavelength. A correct background at the target characteristic X-ray wavelength can be obtained from the X-ray intensity at one location near the characteristic X-ray wavelength, and accurate analysis can be performed even at a low concentration of the target element.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the operation of the present invention.

FIG. 2 is a flowchart of a work procedure according to an embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-285048 (JP, A) JP 61-82149 (JP, A) JP 59-214743 (JP, A) JP 60- 70342 (JP, A) JP 62-287136 (JP, A) JP 62-285047 (JP, A) JP 62-282252 (JP, A) JP 63-313043 (JP, A) JP 58-113741 (JP, A)

Claims (1)

(57) [Claims] 1. A characteristic X-ray peak profile data of a target element is obtained by performing wavelength scanning, a background intensity at the wavelength position of the characteristic X-ray is obtained from this data, and the value and the tail of the peak profile are obtained. The ratio with the X-ray intensity at another nearby wavelength λb is calculated, the X-ray intensity at the characteristic X-ray wavelength of the target element and the above wavelength λb is measured at the time of actual analysis, and the above ratio is added to the X-ray intensity at the above wavelength λb. A background correction method in X-ray spectroscopic analysis, which is obtained by subtracting from the X-ray intensity at the characteristic X-ray wavelength as the background intensity at the characteristic X-ray wavelength of the target element.