JP2006118940A - Method and device for detecting obliquely emitted x-ray - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily set an X-ray extraction angle with respect to dispersion type X-ray spectrometer of a plurality of wavelengths, in oblique emission electron probe microanalyzer (EPMA) analysis. <P>SOLUTION: An analytical sample is mounted on a sample stage, having structure mounted with an inclined angle regulation mechanism on a rotary mechanism. The inclined angle of the analytical sample is set to be brought into the total reflection angle of characteristic X-rays used in the analysis or the extraction angle near thereto, using an energy dispersion type X-ray spectrometer set to the X-ray extraction angle same to those of the wavelength dispersion type X-ray spectrometers. The sample is rotated along the X-ray extraction direction for each wavelength dispersion type X-ray spectrometer to conduct measurements, while keeping the inclined angle of the analysis sample. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electron probe microanalyzer (EPMA) or a scanning electron microscope (analysis SEM) equipped with an X-ray analysis function, which performs elemental analysis using characteristic X-rays detected by irradiating a sample with an electron beam. The present invention relates to an electron probe X-ray analyzer, and more particularly to a method and apparatus for performing an extreme surface analysis by detecting X-rays emitted from a sample surface at a total reflection angle or a take-out angle in the vicinity thereof.

Conventionally, EPMA and analysis SEM are widely used as apparatuses for analyzing a sample surface by irradiating a sample with an electron beam and detecting characteristic X-rays generated from a micron order region. FIG. 5 shows a configuration example of a conventional EPMA equipped with a wavelength dispersive X-ray spectrometer (WDS) and an energy dispersive X-ray spectrometer (EDS) at the same time. Electrons generated from the electron gun 1 are thinly irradiated to the apertured sample 6 by the focusing lens 2 and the objective lens 3. The sample stage 7 and the electron beam deflector 4 can irradiate the analysis position on the sample with an electron beam. Characteristic X-rays generated from the sample are spectrally detected by the WDS spectroscopic element 9 and detected by the WDSX ray detector 10 or detected by the EDS detector 5. X-ray signals of WDS and EDS are sent to the control arithmetic processing unit 16 for data processing.

In normal EPMA analysis, among characteristic X-rays excited by an electron beam accelerated to several kV to several tens kV, characteristic X-rays emitted outside the sample at an angle of approximately 30 to 50 degrees with the sample surface are The solid angle of about 5 to 10 degrees is taken into the X-ray spectrometer. The analysis depth in this case depends on the acceleration voltage of the electron beam and the sample composition, but ranges from about several μm to several μm. In normal EPMA analysis, characteristic X-rays generated from a region where an accelerated electron beam diffuses into the sample are detected, and therefore, analysis of the sample on the extreme surface nanometer order is difficult in principle. In order to solve this problem, Japanese Patent Publication No. 4-61304 discloses a method of analyzing only the extreme surface by detecting characteristic X-rays emitted from the sample surface at the total reflection angle or the extraction angle in the vicinity thereof. Has been.

The above method performed using EPMA is called oblique emission EPMA method (GE-EPMA method: Grazing-exit EPMA). When the oblique emission EPMA method is used, the background X-ray intensity generated from the substrate decreases, so that the surface composition on the nanometer order, ultrathin dirt on the substrate, and analysis of fine particles, which was impossible with normal EPMA analysis Etc. are possible. However, the oblique emission EPMA method requires precise adjustment of the angle (X-ray extraction angle) formed between the sample surface and the emitted X-ray, and is therefore an apparatus provided with an energy dispersive X-ray spectrometer (EDS) in EPMA. An X-ray extraction angle setting condition and an adjustment method when performing measurement are disclosed in Japanese Patent Laid-Open Nos. 2001-208708 and 2002-286661.
Japanese Patent Publication No. 4-61304 JP 2001-208708 A JP 2002-286661 A JP-A-63-76251

When performing analysis with higher accuracy in normal EPMA analysis, WDS is used rather than EDS. Even in the oblique emission EPMA method, the WDS should be able to perform analysis with a higher P / B ratio. However, in the oblique emission EPMA method so far, EDS has been used as an X-ray detector. The reason is that, as described above, in the oblique emission EPMA method, it is necessary to strictly adjust the angle (X-ray extraction angle) formed between the sample surface and the emitted X-ray, but EDS relatively performs the adjustment. Because it is easy

That is, when a large amount of X-ray quanta is incident on the EDS detector, the detection efficiency decreases due to a pile-up phenomenon. Therefore, a device equipped with an X-ray entrance aperture diameter that allows switching of multiple hole diameters on the front surface of the EDS detector so that the EDS detector can be operated while preventing the pile-up phenomenon even when the irradiation current is large. It has become. If a diaphragm for limiting the amount of incident X-rays is used to limit the angle of incident X-rays, the spread of X-rays incident on the detector can be easily set to 1 degree or less. Therefore, it is possible to relatively easily find the sample tilt angle that can be analyzed by the oblique emission EPMA method by finely adjusting the sample angle. However, since the WDS has an incident angle on the spectroscopic element of about 5 to 10 degrees, it is difficult to determine the tilt angle of the sample so that the X-ray emitted from the sample surface has an angle suitable for the oblique emission EPMA method. . An object of the present invention is to provide an apparatus that can easily set an angle suitable for the oblique emission EPMA method even in WDS by utilizing EDS.

In order to solve the above problem, the present invention includes at least one energy dispersive X-ray spectrometer and at least one wavelength dispersive X-ray spectrometer, and the energy dispersive X-ray spectrometer and the wavelength dispersive X-ray spectrometer. An electron probe X-ray analyzer arranged so that an X-ray extraction angle of a line spectrometer is the same as a plane perpendicular to an irradiation axis of an electron beam,
A sample stage having a mechanism in which the sample tilting mechanism is disposed above the sample rotating mechanism and the X, Y, Z axis moving mechanism of the sample;
When detecting X-rays using an X-ray spectrometer selected from either the energy dispersive X-ray spectrometer or the wavelength dispersive X-ray spectrometer, the X-ray is emitted from the analysis sample surface and the analysis sample surface. And a function of setting an inclination angle and a rotation angle of the sample stage so that an angle formed with the X-ray is set to a total reflection angle or an extraction angle in the vicinity thereof.

In the present invention, the energy dispersive X-ray spectrometer is selected, and the sample stage is tilted so that an angle formed with the X-rays emitted from the analysis sample surface is a total reflection angle or a take-out angle in the vicinity thereof. After adjusting the angle and the rotation angle, the angle formed by the X-rays emitted from the analysis sample surface of any of the selected wavelength dispersion X-ray spectrometers is the total reflection angle or the vicinity thereof. It has a function of automatically setting the rotation angle of the sample stage while maintaining the tilt angle so as to set the take-out angle.

Further, the present invention stores data of an angle formed by an arrangement direction of the energy dispersive X-ray spectrometer and the wavelength dispersive X-ray spectrometer with an analysis position as a center with respect to an initial direction of the sample rotating mechanism. A database is provided, and a function of reading necessary data from the database and automatically setting the rotation angle of the sample stage is provided.

In the invention, the energy dispersive X-ray spectrometer has at least one X-ray entrance slit formed on the front surface of the detector so as to be parallel to at least one aperture hole or the sample surface. A function can be set so that only the X-rays satisfying the condition that the angle formed by the X-rays emitted from the sample surface is the total reflection angle or the extraction angle in the vicinity thereof are incident on the energy dispersive X-ray spectrometer. It is characterized by that.

According to the present invention, even for EDS and WDS disposed in different X-ray extraction directions, the angle formed by the X-rays emitted from the analysis sample surface is the total reflection angle or the extraction angle in the vicinity thereof. The sample can be analyzed by oblique emission EPMA method by setting the tilt angle and rotation angle of the sample so that only X-rays satisfying the above condition can be detected.

In addition, according to the present invention, the sample is tilted so as to have an X-ray extraction angle suitable for the oblique emission EPMA method using an EDS having an X-ray incident aperture hole or slit on the front surface of the detector, and the angle is maintained. In this way, the specimen can be automatically rotated in the WDS direction arranged in different X-ray extraction directions, so that X-ray extraction suitable for oblique emission EPMA method can be used even for WDS, which was difficult in the past. The angle can be set easily.

Next, embodiments for carrying out the present invention will be described.
FIG. 1 shows a configuration example when the present invention is implemented by EPMA. A database 19 is added to the configuration example of the conventional EPMA shown in FIG. The database 19 stores data on the positional relationship between the initial direction of the sample rotation mechanism and the X-ray extraction direction of EDS and WDS.

FIG. 2 is a conceptual diagram for explaining the function of the sample stage and the relationship with the X-ray detector according to the present invention, and shows a part corresponding to the sample stage 7 of FIG. 1 in more detail. FIG. 2 shows an example in which the sample rotation mechanism 204 is arranged on the X, Y, and Z axis moving mechanisms of the sample, and the sample tilting mechanism 203 is further arranged thereon. The axis moving mechanisms 205 and 206 may be provided on the sample rotating mechanism 204, and the sample tilting mechanism 203 may be further disposed thereon.

In FIG. 2, the sample rotation mechanism 204 is used to set the tilt direction of the sample tilt mechanism 203 so as to coincide with the direction of the EDS detector 208, and the sample tilt mechanism 203 and the X-ray entrance stop 209 further 2 shows a state in which only the X-ray satisfying the condition that the angle formed by the X-ray emitted from the X-ray is the total reflection angle or the extraction angle in the vicinity thereof is incident on the EDS detector 208. The X-ray entrance stop 209 in FIG. 2 shows a circular stop hole, but it may be a slit parallel to the sample surface. Further, the number of aperture holes and slits having different sizes is not limited to the four shown in the example of FIG. 2, and the arrangement method of the plurality of aperture holes is limited to the mechanism arranged around the disk shown in FIG. It is not something that can be done.
If a small hole diameter or slit width is selected, the conditions for oblique emission EPMA analysis can be set more strictly, but the signal intensity is reduced, so if multiple sizes are prepared, the analyst should use the appropriate size. Will be selected.

Next, FIG. 3 will be specifically described. FIG. 3 is a plan view of the angular arrangement when one EDS and four WDS are mounted as viewed from above the apparatus. In order to facilitate understanding of the essential points of the present invention, the case where the analysis position on the sample (same as the electron beam irradiation axis 212) coincides with the rotation center of the sample rotation mechanism 204 is shown. If the analysis position and the sample rotation center position are different, rotating the sample does not change the sample tilt angle and the analysis position height, but the analysis position moves to a position different from the electron beam irradiation axis. End up. In this case, after rotating the sample at the analysis point, the operator confirms the analysis position with a secondary electron image, a backscattered electron image, an optical microscope image, etc., and the X, Y axis moving mechanism 205, 206 is used to determine the analysis position. What is necessary is just to make it correspond to the irradiation axis 212. Alternatively, as disclosed in Japanese Patent Laid-Open No. 63-76251, the amount of movement of the analysis point with rotation is obtained by calculation, and the amount of movement is fed back to the X, Y movement control system, so that the operator It is also possible to automatically move the analysis position to the electron beam irradiation axis 212 regardless of the work.
If a sample stage having a structure in which the electron beam irradiation axis and the sample rotation center always coincide is used, correction of the analysis position is not required even if the sample is rotated. However, in the present invention, the electron beam irradiation axis and the sample are not necessarily corrected. It is not necessary to use a sample stage having a structure in which the rotation centers coincide.

The sample rotation initial direction 308 is a position determined by design according to the specifications and structure of the apparatus. Accordingly, the angles θ0 to θ4 formed by the sample rotation initial direction 308 and the EDS 303 and WDS 304 to 307 are also determined by design by the apparatus. The arrangement shown in FIG. 3 is merely an example, and it goes without saying that the sample rotation initial direction, the positional relationship between EDS and WDS, the WDS radix, the angle between the spectroscopes, and the like vary depending on the apparatus.

As described above, after setting the angle by the sample tilt mechanism 203 so that the characteristic X-ray of a certain wavelength (or the same as the energy) becomes the condition of the oblique emission EPMA analysis by the EDS detector 208, the characteristic of the certain wavelength is set. The sample is rotated while maintaining the tilt angle of the sample so that the X-ray extraction direction coincides with any WDS spectrometer direction selected to detect X-rays. At this time, the control arithmetic processing unit 16 reads the angular arrangement of the spectroscope stored in the database 19 and sets the sample at a necessary rotation position by the sample rotation mechanism 204.

FIG. 4 shows an analysis flow in which the above-described embodiment of the present invention is summarized.
Step 1: Mount the analysis sample on the sample stage. At this time, it is mounted so that the X-ray extraction direction from the sample surface coincides with the sample inclination direction.
Step 2: Specify the characteristic X-ray type of the element for which oblique emission EPMA analysis is performed.
Step 3: Read θ 0 from the database 19 and rotate the sample by the sample rotation mechanism 204 so that the tilt direction of the sample tilt mechanism 203 matches the direction in which the EDS detector 208 is installed.
Step 4: The tilt angle is set by tilting the sample by the sample tilt mechanism 203 so that the characteristic X-rays detected by the EDS detector 208 are the conditions for the oblique emission EPMA analysis.
Step 5: Designate a WDS spectrometer for spectroscopic detection of the characteristic X-ray species of the element for which oblique emission EPMA analysis is performed. The designated WDS spectrometer may be set to the spectral condition in this step, or when the characteristic X-ray type is designated in step 2, a spectroscope capable of spectroscopic / detecting the characteristic X-ray type is already set. May be.
Step 6: Corresponding to the designated WDS spectrometer, necessary data is read from the database 19 from θ1 to θ4, and the sample is rotated by the sample rotating mechanism 204 while maintaining the tilt angle. If the analysis position deviates from the electron beam irradiation axis due to rotation, it is corrected by the X and Y axis moving mechanism.
Step 7: Oblique emission EPMA analysis is performed with the designated WDS spectrometer.
Step 8: When analyzing by changing the analysis element / characteristic X-ray type, select Yes and repeat Step 2 and subsequent steps. Select No to end the analysis.

1 is a configuration example of an electronic probe microanalyzer according to the present invention. The conceptual diagram for demonstrating the function of the sample stage concerning this invention, and the relationship with an X-ray detector. The top view for demonstrating the position and operation | movement relationship of the sample stage and X-ray detector concerning this invention. The flowchart explaining embodiment of this invention. The structural example of the conventional electronic probe microanalyzer.

Explanation of symbols

(The following items 1 to 18 are common to FIGS. 1 and 5, and 19 is attached only to FIG. 5.)
1: Electron gun 11: WDS spectroscopic element control device
2: Focusing lens 12: WDSX ray signal processor
3: Objective lens 13: Sample stage controller
4: Electron beam deflector 14: Interface
5: EDS detector 15: EDS controller
6: Sample 16: Control processing unit
7: Sample stage 17: Display device
8: Electro-optical system controller 18: Input device
9: WDS spectrometer 19: Database
10: WDSX ray detector

Claims (3)

At least one energy dispersive X-ray spectrometer and at least one wavelength dispersive X-ray spectrometer are provided, and an X-ray extraction angle of the energy dispersive X-ray spectrometer and the wavelength dispersive X-ray spectrometer is an electron. An electron probe X-ray analyzer disposed so as to be the same with respect to a plane perpendicular to the irradiation axis of a line, and a sample stage having a structure in which a sample tilting mechanism is disposed on a sample rotating mechanism With
By selecting the energy dispersive X-ray spectrometer, the tilt angle and rotation angle of the sample stage are set so that the angle formed with the X-rays emitted from the surface of the analysis sample becomes the total reflection angle or the extraction angle in the vicinity thereof. After the adjustment, the angle formed by the X-rays emitted from the analysis sample surface is set to the total reflection angle or the extraction angle in the vicinity thereof for any of the selected wavelength dispersion X-ray spectrometers. A surface analysis method for performing X-ray analysis by setting the rotation angle of the sample stage while maintaining the tilt angle so as to satisfy the following conditions. By selecting the energy dispersive X-ray spectrometer, the tilt angle and rotation angle of the sample stage are set so that the angle formed with the X-rays emitted from the surface of the analysis sample becomes the total reflection angle or the extraction angle in the vicinity thereof. After the adjustment, the angle formed by the X-rays emitted from the analysis sample surface is set to the total reflection angle or the extraction angle in the vicinity thereof for any of the selected wavelength dispersion X-ray spectrometers. In order to set the rotation angle of the sample stage while maintaining the tilt angle so as to satisfy the following conditions, the energy dispersive X-ray spectrometer centered on the analysis position with respect to the initial direction of the sample rotation mechanism And a database for storing data of angles formed by the arrangement directions of the wavelength dispersive X-ray spectrometers, and reading the necessary data from the database to automatically set the rotation angle of the sample stage. With features, electron probe X-ray analysis apparatus according to claim 1. The energy dispersive X-ray spectrometer has at least one X-ray entrance slit or aperture hole formed in front of the detector so as to be parallel to the sample surface, and is emitted from the analysis sample surface. 3. A function capable of setting so that only X-rays satisfying a condition that an angle formed with a line is a total reflection angle or an extraction angle in the vicinity thereof is incident on the energy dispersive X-ray spectrometer. The electron probe X-ray analyzer described in 1.

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