JP2001133420A - Method and apparatus for total reflection x-ray fluorescence analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus, for a total reflection X-ray fluorescence analysis, in which a part near the side end face of a sample can be analyzed and in which the sample can be used effectively. SOLUTION: In this total reflection X-ray fluorescence analysis, a visual-field limitation member 6 which comprises a plurality of slits is arranged between a sample 50 and an X-ray detector 4 so as to be capable of being changed over. When a part near the side end face of the sample is analyzed, the limitation member is changed over to a second slit 62 whose opening area is smaller than that of a first slit 61 used for an ordinary analysis. A visual field is limited in such a way that fluorescent X-rays and scattered X-rays from the side end face of the sample are not taken into the X-ray detector 4. Consequently, even when the part near the side end face of the sample is analyzed, the fluorescent X-rays and the scattered X-rays from the side end face of the sample are not taken into the X-ray detector 4, and the sample 50 including the part near the side end face can be analyzed as a whole. A specific place which is narrower than the sample can be analyzed by the second slit 62.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a total reflection X-ray fluorescence spectrometer that irradiates a line at a small incident angle and analyzes X-ray fluorescence from a surface layer of a sample.

[0002]

2. Description of the Related Art In general, a total reflection X-ray fluorescence spectrometer is known as a device capable of non-destructively analyzing trace impurities contained in a surface layer of a sample with high sensitivity. FIG. 7 shows an example of a conventional total reflection X-ray fluorescence spectrometer. Primary X-rays B1 emitted from an unillustrated X-ray source are applied to the surface 51 of the sample 50 at a small incident angle α (for example, about 0.05 ° to 0.20 °).
A part of the incident primary X-ray B1 is totally reflected and becomes a reflected X-ray B2, and another part excites the sample 50 to generate a fluorescent X-ray B3 unique to the element constituting the sample 50.
The fluorescent X-rays B3 are incident on an X-ray detector 4 such as a semiconductor detector (SSD) arranged to face the sample surface 51.
The X-ray fluorescence B3 incident on the X-ray detector 4
After the X-ray intensity is detected, the target X-ray spectrum is obtained by the multiplex height analyzer 5 based on the detection signal a from the X-ray detector 4.

In this type of total reflection X-ray fluorescence spectrometer, since the incident angle α of the primary X-ray B1 is very small, the reflected X-ray B
2 and scattered X-rays are less likely to be incident on the X-ray detector 4, and there is an advantage that the noise is smaller than the output level of the fluorescent X-rays B3 detected by the X-ray detector 4. That is, a large S / N ratio can be obtained, and therefore, there is an advantage that the analysis accuracy is high and, for example, even a trace amount of impurities can be detected.

[0004]

However, when the sample 50 is a silicon (Si) wafer, a magnetic disk or the like,
As shown in FIG. 8, in general, for example, the side edge (edge portion) 54 of the silicon wafer 50 is more contaminated than the central portion 55, and therefore, the vicinity 53 of the edge portion is irradiated with the primary X-ray B1. Need to be analyzed. In this case, as described above, since the incident angle α of the primary X-ray B1 is extremely small, it is inevitable that the spot diameter D (FIG. 7) in the irradiation direction of the primary X-ray B1 becomes large, and the silicon wafer 50
May be irradiated with the primary X-rays B1. The reflection X of silicon (Si) from the edge
When a disturbance line B4 such as a ray or a scattered X-ray enters the X-ray detector 4, the S / N ratio is significantly reduced. Therefore, the range of the edge portion vicinity 53 that can be analyzed is the edge portion 5
4 is limited to a range where the disturbance line B4 does not occur, that is, a range excluding a portion sufficiently close to the edge portion 54. As a result, it was difficult to analyze a portion sufficiently close to the edge portion 54.

An object of the present invention is to solve the above problems and to provide a total reflection X-ray fluorescence analysis method and apparatus capable of analyzing the entire sample including the vicinity of the side end face.

[0006]

According to a first aspect of the present invention, there is provided a total reflection X-ray fluorescence X-ray analysis method, comprising the steps of: providing a primary X-ray from an X-ray source at a small incident angle toward a sample surface; A fluorescent X-ray from a sample that has received the primary X-rays is detected by an X-ray detector facing the sample surface, and a predetermined amount of the sample is provided between the sample and the X-ray detector. A field of view having a plurality of slits including a first slit for restricting the field of view so as to capture fluorescent X-rays from the measurement site into the X-ray detector, and a second slit having an opening area smaller in diameter than the first slit When the restricting member is switchably arranged, and when measuring near the side end surface of the sample, the second X-ray detector is configured to prevent fluorescent X-rays and scattered X-rays from the side end surface of the sample from being taken into the X-ray detector. The slit restricts the visual field.

The total reflection X-ray fluorescence analyzer according to claim 2
Primary X-rays from a source are incident on the sample surface at a small predetermined angle of incidence, and X-ray detectors facing the sample surface detect fluorescent X-rays from the sample that has received the primary X-rays That is disposed between the sample and the X-ray detector,
A first slit for restricting the field of view so as to capture fluorescent X-rays from a predetermined measurement site of the sample into the X-ray detector;
A field limiting member having a plurality of slits including a second slit having an opening area smaller in diameter than the slit, and switching each slit of the field limiting member to measure the vicinity of the side end surface of the sample. Switching means for restricting the field of view by the second slit so that the X-ray detector does not take in fluorescent X-rays and scattered X-rays from the side end surface of the sample.

According to the first or second aspect of the present invention, in the total reflection X-ray fluorescence analysis, a field limiting member having a plurality of slits between the sample and the X-ray detector is switchably disposed, and When analyzing the vicinity of the side end face, the X-ray detector is switched to a second slit having an opening area smaller in diameter than the first slit used for normal analysis, and the X-ray detector detects fluorescent X-rays and scattered X-rays from the side end face of the sample. Limit the field of view so that lines are not captured. Therefore, even in the analysis near the side end surface of the sample, the fluorescent light and the scattered X-ray from the side end surface of the sample can be taken into the X-ray detector by the second slit having the small-diameter opening area. Therefore, the analysis of the entire sample including the vicinity of the side end face can be performed. In addition, the second slit allows analysis of a narrow specific portion of the sample.

The total reflection X-ray fluorescence spectrometer according to a third aspect of the present invention includes a correction means for correcting the X-ray intensity detected by the X-ray detector in accordance with the opening area of each slit of the visual field limiting member. Have. Therefore, the X-ray intensity can be automatically corrected according to the opening area of each slit.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic side view of a total reflection X-ray fluorescence spectrometer according to one embodiment of the present invention. In this apparatus, an X-ray source 2 for generating X-rays, and a primary X-ray B1 that is monochromatic by diffracting X-rays is made incident on the surface of a sample 50 on a sample stage 70 at a small predetermined incident angle. A spectral crystal (monochromator) 3 and an X-ray detector 4 such as a semiconductor detector (SSD) for detecting fluorescent X-rays B3 from the sample 50 that has received the primary X-rays B1 and facing the surface of the sample 50 are provided. ing. An arbitrary position on the sample 50 is irradiated with the primary X-rays B1 by rotating and linearly moving the sample table 70 on which the sample 50 is placed by driving means (not shown).

The apparatus further comprises a field limiting member 6 disposed between the sample 50 and the X-ray detector 4 and having a plurality of slits, and switching means 7 for switching each slit of the field limiting member 6. I have. In addition, the present apparatus has an X-ray detector 4
A correcting means 8 for correcting the X-ray intensity detected in step 4 in accordance with the opening area of each slit of the visual field limiting member 6, and a multiple wave height analyzer for obtaining an X-ray spectrum based on the detection signal a from the correcting means 8. 5 is provided. X-ray source 2 and part of X-ray detector 4, spectral crystal 3, field limiting member 6, sample 5
0 and the sample stage 70 are arranged in the vacuum chamber 22.

FIGS. 2 to 4 show an example of the visual field limiting member 6 and the switching means 7. As shown in a partially cutaway side view of FIG. 2A, the view restricting member 6 disposed in the vacuum chamber 22 of the present apparatus extends in the longitudinal direction (in this figure, the direction perpendicular to the paper surface), Start-up portions 6 formed on both sides
a and the bottom 6c is substantially U-shaped in cross section. A plurality of slits are formed in the bottom part 6c, and a protruding part 6b that protrudes inward is formed in the rising part 6a.
The X-ray detector 4 having the SSD element 4e has a guide portion 24. The guide portion 24 is formed on both outer sides with a groove portion 24b fitted with the protrusion 6b and a window portion 4a of the X-ray detector 4. An opening 24a having the same opening area. The view restricting member 6 is attached to the guide 24 so as to be movable in the longitudinal direction of the view restricting member 6 in a state where the protrusion 6b and the groove 24b are fitted.

As shown in a partially broken plan view of FIG.
The field-of-view restricting member 6 includes, for example, a first slit 61 for restricting the field of view so that the X-ray detector 4 takes in fluorescent X-rays B3 from a normal measurement site of the sample 50, and an opening having a smaller diameter than the first slit 61. A second slit 62 having an area, a third slit 63 in which the filter 65 is fitted with the same opening area as the first slit 61, and a fourth slit in which the filter 65 is fitted with the same opening area as the second slit 62. Are arranged side by side on a straight line. For the filter 65, for example, a polyimide resin is used for silicon (Si). The field-of-view limiting member 6 is supported by a rod-like slit support 26 extending in the longitudinal direction. A knob 26a is formed at the tip of the slit support portion 26.

As shown in the partially broken front view of FIG.
The slit supporting portion 26 for supporting the view restricting member 6 is provided on the flange portion 3 fixed to the outer surface of the vacuum chamber 22 of the present apparatus.
1 is movably attached in the longitudinal direction X via a cylindrical collar portion 38. A mounting plate 32 is mounted on the upper portion of the flange portion 31. The mounting plate 32 is fixed by bolts 72 to a bracket 71 fixed to a gantry 33 supporting the entire apparatus. A guide portion 35 for guiding the slit support portion 26 in the longitudinal direction X is attached to the mounting plate 32 with a bolt 73, and a sensor for supporting a sensor portion 36 for detecting the positions of the slits 61 to 64 in FIG. A support bracket 37 is attached.
O-rings 39 and 40 are fitted between the slit support portion 26 and the collar portion 38 and between the flange portion 31 and the vacuum chamber 22, respectively, and a cap seal 41 is fitted between the collar portion 38 and the flange portion 31 in FIG. Thus, the vacuum in the vacuum chamber 22 is maintained.

As shown in FIG. 3, the switching means 7 arranged outside the vacuum chamber 22 is fixed to the slit support portion 26, is arranged side by side, and is a positioning plate movable in the longitudinal direction X. And a positioning knob 4 having a spring-mounted knob shaft 43a attached to the mounting plate 32 and movable in a direction Y orthogonal to the longitudinal direction X of the positioning plate 42.
And 3. The positioning plate 42 has a plurality of notches 42 into which the tips of the knob shafts 43a are fitted along the longitudinal direction X in accordance with the number and positions of the slits of the visual field limiting member 6.
a is provided. Positioning knob 43 against spring force
With the tip of the knob shaft 43a detached from the positioning plate 42, the slit support portion 26 is manually moved left and right to perform alignment, and the tip of the knob shaft 43a is inserted into a predetermined notch portion 42a by a spring force. The fitting restricts the positioning of the visual field limiting member 6.

The respective intervals between the plurality of notches 42 of the positioning plate 41 and the respective intervals between a plurality of sensors such as a photosensor of the sensor portion 36 attached to the sensor support bracket 37 are set to be the same. When the positioning is performed, the shielding plate 27 fixed to the slit supporting portion 26 shields each sensor of the sensor portion 36 to detect the position of each slit. Since the X-ray intensity detected by the X-ray detector 4 changes when the opening area of the field-of-view limiting member 6 changes, the correction means 8 in FIG. By correcting the X-ray intensity detected in 4 according to the opening area of each slit, the original X-ray intensity can be obtained. That is, I ₀
Is the X-ray intensity when the normal aperture area (the aperture area of the first slit 61), the X-ray intensity when the aperture area of the slit where I is switched (the aperture area of the second slit 62), and K is the aperture When a correction coefficient corresponding to the area is used, correction is performed using the following equation. I = K · I _{0 A} target X-ray spectrum is obtained by the multiplex height analyzer 5 based on the detection signal a from the correction means 8.
Thus, when the visual field limiting member 6 is switched, the X-ray intensity can be automatically corrected according to the opening area of each slit.

The first slit 61 shown in FIG. 3 is used for analyzing a predetermined measurement site separated from the edge of the sample (for example, 10 mm or more). The second slit 62 is used when analyzing a measurement site near the edge. The third and fourth slits 63 and 64 are used for the same analysis as the first and second slits 61 and 62, respectively.
The filter 65 is used to cut a fluorescent X-ray of a light element such as silicon (Si) to lower the background.

Next, the operation at the time of analysis will be described. First, when analyzing the main part of the surface (measurement surface) of the sample 50 except for the vicinity of the edge, as shown in FIG. 2A, the switching means 7 switches to the first slit 61 of the visual field limiting member 6. Can be In this state, the sample 50 is moved in the XY directions by the sample stage 70, and so-called mapping measurement in which the fluorescent X-ray intensity is measured at many positions is performed. Thus, contamination and defects of the main part of the sample 50 are checked.

When analyzing a measurement site near the edge,
As shown in FIG. 2B, the sample stage 70 is moved in the X and Y directions, and is switched to the second slit 62 of the visual field limiting member 6 by the switching means 7 in FIG. In this case, even if the measurement site is located near the edge portion 54 of the sample 50, the reflected X-rays and scattered X-ray
A disturbance line B4 such as a line is shielded by the second slit 62 and is not taken into the window 4a of the X-ray detector 4.

For example, the beam width of the primary X-ray B1 is 26 m
m, the beam thickness is 10 μm, the incident angle α is 0.09 °, and the first slit 61 having a diameter of 13 mm is used.
As shown in (c), the measurement site M represented by the measurement center must be separated from the edge 54 by 12 mm or more.
There is a possibility that a disturbance line B4 from the X-ray detector 4 enters the X-ray detector 4 through the first slit 61. In contrast, the diameter 5
When the second slit 62 of 2 mm is used, as shown in FIG. 2D, even when the measurement site M is brought close to the edge portion 54 by about 4 mm, the disturbance line B4 from the edge portion 54 is And is prevented from entering the X-ray detector 4. In addition, when it is desired to analyze a specific narrow region of the sample 50 other than the proximity of the edge portion 54, the second slit 62 can be used.

FIG. 5 shows that when the sample 50 is a silicon wafer, the diameter of the Si-Kα line at the edge is 1 mm.
The case where the first slit 61 of 3 mm is used and the case where the diameter is 5 m
A comparison with the case where the second slit 62 of m is used is shown.
The vertical axis indicates the Si-Kα line intensity (cps), and the horizontal axis indicates the distance from the edge. As shown in this figure, the first slit 61
(13 mm in diameter) compared to the second slit 62 (5 mm in diameter).
mm), the intensity of the background Si-Kα ray is low even in the vicinity of the edge portion. For example, at a position 10 mm away from the edge,
The strength (82 in the figure) of the slit having a diameter of 5 mm is 1 mm in diameter.
This is considerably lower than the strength at the slit of 3 mm (illustration 81). Thus, highly accurate analysis near the edge of the sample 50 is possible.

FIG. 6 shows one edge from the edge in FIG.
An example of an X-ray spectrum measured at a position separated by 0 mm is shown. FIG. 6A shows a case where the first slit 61 (13 mm in diameter) is used at the measurement position 81 shown in FIG.
5 shows the case where the second slit 62 (5 mm in diameter) is used at the measurement position 82 shown in FIG. The vertical axis indicates relative intensity, and the horizontal axis indicates energy (keV). In FIG. 6A, Si
Backgrounds such as -Kα pile-up peak and W-Lβ escape peak are large, and in FIG. 6B, these backgrounds are small. Therefore, when the second slit 62 is used in the vicinity of the edge, the background can be reduced as compared with the first slit 61, and highly accurate analysis in the vicinity of the edge of the sample 50 becomes possible. .

In this embodiment, each of the slits of the field limiting member is arranged in series, and is a slide type in which the slits are moved forward and backward in the longitudinal direction to switch. However, the field limiting member is formed in a disk shape.
A rotary type in which each slit is arranged on a circumference and rotated around its axis to switch the slit may be used.

In this embodiment, the switching of the visual field limiting member 6 is manually performed. However, a drive mechanism is provided on the positioning plate 42 of the switching means 7 shown in FIG. Switching may be performed automatically based on a switching signal output from a not shown).

[0025]

As described above, according to the present invention, in total reflection X-ray fluorescence analysis, a field limiting member having a plurality of slits is switchably arranged between a sample and an X-ray detector.
When analyzing near the side end face of the sample, the X-ray detector is switched to a second slit having an opening area smaller in diameter than the first slit used for normal analysis, and the X-ray detector detects the fluorescence X from the side end face of the sample.
The field of view is restricted so that no rays and scattered X-rays are captured. Therefore, even when the analysis is performed in the vicinity of the side end face of the sample, the fluorescent X-rays and scattered X-rays from the side end face of the sample are not taken into the X-ray detector. Analysis becomes possible. In addition, the second slit allows analysis of a narrow specific portion of the sample.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a total reflection X-ray fluorescence spectrometer according to one embodiment of the present invention.

2 (a) to 2 (d) are schematic side views, partially broken away, showing main parts of the device.

FIG. 3 is a schematic plan view showing a main part of the device.

FIG. 4 is a schematic front view showing a main part of the device.

FIG. 5 is a characteristic diagram showing a Si-Kα ray near an edge of a sample.

FIG. 6 is a characteristic diagram showing an example of an X-ray spectrum near an edge of a sample.

FIG. 7 is a schematic configuration diagram showing a conventional total reflection X-ray fluorescence spectrometer.

FIG. 8 is an enlarged sectional view near a side end surface of a sample.

[Explanation of symbols]

2 X-ray source, 4 X-ray detector, 6 View limiting member, 7
Switching means, 8 correction means, 50 sample, 61 first slit, 62 second slit, B1 primary X-ray, B3
... X-ray fluorescence.

Claims (3)

[Claims] 1. A primary X-ray from an X-ray source is incident on a sample surface at a minute predetermined angle of incidence, and the sample receives the primary X-ray from an X-ray detector facing the sample surface. A total reflection X-ray fluorescence analysis method for detecting X-ray fluorescence, wherein a field of view is restricted between the sample and the X-ray detector so that X-ray fluorescence from a predetermined measurement site of the sample is taken into the X-ray detector. A first slit to be formed, and a view restricting member having a plurality of slits including a second slit having an opening area smaller in diameter than the first slit are arranged so as to be switchable, and the vicinity of the side end surface of the sample is measured. A total reflection X-ray fluorescence analysis method for limiting the field of view by the second slit so that the X-ray detector does not take in the X-ray fluorescence and the scattered X-ray from the side end face of the sample. 2. A sample which receives primary X-rays from an X-ray source at a minute predetermined angle of incidence toward a sample surface and receives the primary X-rays from an X-ray detector opposed to the sample surface. A total reflection X-ray fluorescence analyzer for detecting X-ray fluorescence, wherein the X-ray fluorescence detector is disposed between the sample and the X-ray detector, and captures X-ray fluorescence from a predetermined measurement site of the sample into the X-ray detector. A field limiting member having a plurality of slits including a first slit for restricting a field of view and a second slit having an opening area smaller in diameter than the first slit; and switching each slit of the field of view restricting member to the sample. Switching means for restricting the field of view by the second slit so that the X-ray detector does not take in fluorescent X-rays and scattered X-rays from the side end face of the sample when measuring near the side end face of the sample. Total reflection X-ray fluorescence analyzer 3. The total reflection X-ray fluorescence analysis according to claim 2, further comprising a correction unit configured to correct the X-ray intensity detected by the X-ray detector in accordance with an opening area of each slit of the visual field limiting member. apparatus.