JPH04364455A - Surface analyzing method - Google Patents

Abstract

PURPOSE:To make it possible to perform the quantitative analysis of the surface of the pole of a sample in high accuracy by measuring the characteristic X-ray intensity of each element with the acceleration voltage of an electron beam, storing the characteristic X-ray intensity of the standard sample of each element, extending the correlation curve of the acceleration voltage of each element and the X-ray intensity ratio to the side of the low acceleration voltage, and obtaining the X-ray intensity ratio. CONSTITUTION:A spectroscope A is formed of a spectroscopic crystal 4 and a detector 5. Both devices have the constant relationship, and the wavelength is scanned. The spectroscopic crystal 4 divides the X rays emitted from the sample, and the X rays are detected with the detector 5. The speed of the electron beam from an electron gun 1 is controlled with an acceleration power supply part 7. The wavelength scanning is controlled with a spectroscope control part 8. An acceleration voltage and the spectroscopic wavelength are added to the detected signal of the detector 5. The results are stored in a memory part 11, and the data are processed. The X-ray intensity at the minimum exciting voltage of the sample element is obtained, and the quantitative analysis of the surface of the pole is performed. The concentration distribution of each element can be measured highly accurately by obtaining the X-ray intensity at the minimum exciting voltage of each element.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantitatively analyzing the extreme surface of a sample using an electron beam microanalyzer or the like.

0002

[Prior Art] In order to perform quantitative analysis on the extreme surface, it is necessary to irradiate the sample with an electron beam at the lowest possible accelerating voltage, but there are differences in the energy required to excite the X-rays depending on the element. Conventionally, all of the elements to be measured were irradiated with an electron beam of energy capable of exciting X-rays. Therefore, there was a problem in that the resolution accuracy in the depth direction deteriorated. In addition, if you try to measure all elements by exciting them with the minimum excitation energy of each element, the measurement time will be too long because the standard sample of each element must be measured at the same acceleration voltage as the sample measurement. There was a problem.

0003

SUMMARY OF THE INVENTION An object of the present invention is to enable highly accurate quantitative analysis of the extreme surface of a sample using an electron beam microanalyzer.

0004

[Means for solving the problem] In extreme surface analysis using an electron beam microanalyzer, etc., the acceleration voltage of the electron beam is set at several points at appropriate intervals, and the characteristic X-ray intensity of each element is measured at each set acceleration voltage. At the same time, the characteristic X-ray intensity of the standard sample of each element at each acceleration voltage is measured and memorized in advance, and the X-ray intensity ratio I of each element i is calculated for each acceleration voltage.
i is calculated, and a correlation curve between the accelerating voltage and the X-ray intensity ratio calculated above is determined for each element, and the X-ray intensity ratio at the minimum excitation voltage of each element is shifted to the lower accelerating voltage side. After extrapolation and extension, ZAF correction calculations were performed based on these values to determine the concentration of each element at the extreme surface.

[0005]

[Operation] When the electron acceleration voltage is gradually increased from a point below the lowest excitation voltage of a certain element in a uniform concentration sample, the characteristic X-ray intensity of that element suddenly rises at the lowest excitation voltage. , will gradually increase thereafter and change as shown by the solid line P in FIG. In reality, due to variations in the accelerating voltage and the effects of excitation efficiency, the rising point has a sloping shape as shown by the dotted line in Fig. 4, but the characteristic X-ray intensity at this rising point S is based on the characteristic X-ray intensity curve. is extrapolated from the high excitation voltage side, and the lowest excitation voltage on the horizontal axis is 0.
It can be determined as the point of intersection with the perpendicular line erected at . When electrons are incident on the sample surface, the electrons enter the sample while losing energy, and during this time the sample emits X-rays. When the accelerating voltage of electrons is the lowest excitation voltage of a certain element, the electrons incident on the sample surface have energy less than the lowest excitation voltage of the element at a point a little further from the sample surface. The characteristic X-ray intensity of the above elements emitted from the sample shows information only on the very surface of the sample. Next, consider a sample with a uniform concentration of the target element, and a non-uniform sample where the surface concentration is the same as this uniform sample, but the concentration changes in the depth direction. As the excitation voltage is increased, the characteristic X-ray intensity of the target element changes as shown by Q or R in Figure 4 depending on the concentration distribution in the depth direction. If we extend the intersection point with the perpendicular line at the lowest excitation voltage, all of them will be point S because the surface concentration is the same. In other words, even if the concentration distribution of the target element in the sample in the depth direction is not uniform, the characteristic X-ray intensity when extrapolated from the high electron acceleration voltage to the low electron acceleration voltage to the lowest excitation voltage is shows the value on the surface of Therefore, it can be said that the value at the extrapolated minimum excitation voltage of the X-ray intensity ratio indicates the value at the outermost surface.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a configuration diagram of an embodiment of the present invention. S
1 is a sample, and 1 is an electron gun, which is composed of a cathode 1A that emits electrons, a grid 1B that narrows the electrons, and an anode 1C that accelerates the electrons. 2 is a lens 1 that converges the electron beam, 3 is a lens 2 that scans and converges the electron beam, and the spectrometer A is composed of a spectroscopic crystal 4 and a detector 5, and the spectrometer drive unit maintains a constant relationship between the two. 6 to perform wavelength scanning. The spectroscopic crystal 4 spectrally spectra the X-rays emitted from the sample. The detector 5 detects the X-rays separated by the spectroscopic crystal 4. 7 is the acceleration power supply section, grid 1B
The irradiation speed, that is, the irradiation energy of the electron beam is controlled by changing the voltage between the anode 1C and the anode 1C. Reference numeral 8 denotes a spectrometer control section that controls the wavelength scanning of the spectrometer A. 9 is CPU
Then, the electron beam speed of the electron gun 1 is controlled by the acceleration power supply section 7, and the wavelength scanning is controlled by the spectrometer control section 8, and the acceleration voltage and the spectral wavelength are added to the signal obtained by the detector 5. The stored data is stored in the storage unit 11, and the data processing described below is performed using the measurement data of the standard sample stored in the storage unit 11, and the X-ray intensity at the minimum excitation voltage of the sample element is determined. Perform quantitative analysis of 10 is a CRT, which displays the results on the screen.

The control operation in the CPU 9 will be explained using the flowchart shown in FIG. In order to execute step #5, measurement data for a standard sample with uniform concentration is collected in advance. First, the irradiation energy of the electron beam is determined at a certain acceleration voltage, and qualitative analysis of all elements is performed (#1). Data processing (peak search, calculation of peak intensity value PK, background value BG, determination of element name) is performed, and the detected element is confirmed (#2). Several excitation voltages of the electron beam used for measurement are determined corresponding to the detected element (#3). Measure the characteristic X-ray intensity of each detected element at several determined excitation voltage points (
#4). Read the measurement data of the standard sample of each detected element at the same excitation voltage as the above measurement from the storage unit 11 (#5)
, for each element, the characteristics X in the measurement sample and standard sample
The ratio of ray intensities, that is, the X-ray intensity ratio Ii, is expressed as Ii=(PKSi-BGSi)/(PKHi-BGHi
) However, S indicates the measurement sample, H indicates the standard sample, and i indicates the data for element i. Calculate (#6). Plot this on a graph as shown in Figure 3 (#7). A curve connecting the plotted points is assumed as a quadratic or cubic equation by the least squares method or the like, and the X-ray intensity ratio at the minimum excitation voltage of each element is estimated (#8). The estimated X-ray intensity ratio is ZAF
(atomic number effect, absorption effect, fluorescence excitation effect) correction (#
9) Display the obtained value on the CRT 10 (#10).

In the above embodiment, the X-ray intensity used for calculating the X-ray intensity ratio is calculated by simply subtracting the background value BG from the measured peak intensity PK, and the irradiation current is not taken into account. Since the current is a parameter of the electron beam irradiation intensity, the X-ray intensity ratio Ii is calculated by multiplying the above calculation value by the irradiation current value PC, and is calculated as Ii=(PKSi-BGSi)PCSi/(P
Even if the concentration of each element is determined by calculating KHi-BGHi)PCHi, the same effect as described above can be obtained.

[0009]

[Effects of the Invention] According to the present invention, it has become possible to determine the X-ray intensity ratio of each element at the minimum excitation voltage, and it has become possible to measure the concentration distribution of each element on the extreme surface with high precision. Ta.

[Brief explanation of the drawing]

[Fig. 1] Block diagram of one embodiment of the present invention

[Figure 2] Flowchart of the above embodiment

[Figure 3] Correlation curve diagram between excitation voltage and X-ray intensity ratio of each element in the above example

[Figure 4] Correlation curve diagram between excitation voltage and X-ray intensity in the above example

[Explanation of symbols]

S Sample 1 Electron gun 1A Cathode 1B Grid 1C Anode 2 Level 1 3 Level 2 4 Spectroscopic crystal 5 Detector 6 Spectrometer drive unit 7 Acceleration power supply section 8 Spectrometer control section 9 CPU 10 CRT 11. Storage section

Claims (2)

[Claims] Claim 1: The acceleration voltage of the electron beam is set at several points at appropriate intervals, the characteristic X-ray intensity of each element is measured at each set acceleration voltage, and a standard sample of each element at each acceleration voltage is measured in advance. Measure and store the characteristic X-ray intensity at , calculate the X-ray intensity ratio Ii of each element i for each acceleration voltage, and calculate the correlation curve between the acceleration voltage and the calculated X-ray intensity ratio for each element. and the X-ray intensity ratio at the minimum excitation voltage of each element is obtained by extrapolating and extending the above-obtained correlation curve to the low acceleration voltage side to obtain the concentration of each element at the extreme surface. Analysis method. [Claim 2] The X-ray intensity ratio Ii of each element i is
Ii=(PKSi−BGSi)PCSi/(PKHi−
BGHi) PCHi where PK is the peak intensity, BG is the background value, PC is the irradiation current value, and the subscript indicates the type of data, S is the measurement sample, H is the standard sample, and i is the element i. 2. The surface analysis method according to claim 1, wherein the surface analysis method is obtained by calculation.