JPH10232207A - All reflection fluorescent x-ray analyzing method and all reflection fluorescent x-ray analyzing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for analyzing all reflection fluorescent X-rays which are performed precisely and readily Al analyzation in a sample containing Al with Si being employed as a main component. SOLUTION: First, secondary X-rays 9 from a to-be-analyzed sample 8 is detected through a filter 12 made of Al, and under the state, primary X-rays 5 irradiate a blank sample 7 uncontaining Al, to acquire Al spectrum ray strength (filter interference strength). Further, the sum total of strength of secondary X-rays (blank sum total) having more than a specific energy level exciting Al is acquired, and correlation between the blank sum total and filter interference strength is acquired. Next, the primary X-rays 5 are irradiated on the to-be-analyzed sample 8, and the sum totals of Al spectrum ray strength (sample strength) and strength of the secondary X-rays having more than the specific energy level are acquired. The filter interference strength is acquired using the above correlation from this sample sum total, and is subtracted from sample strength acquired previously to acquire actual strength of Al spectrum ray.

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 analysis method and apparatus for detecting an aluminum component contained in a sample containing silicon as a main component such as a semiconductor wafer. is there.

[0002]

2. Description of the Related Art Conventionally, a total reflection X-ray fluorescence analysis method is used.
For example, when analyzing aluminum on a silicon wafer, a spectroscope that monochromatizes X-rays generated from an X-ray source and makes the X-rays incident on a detector in order to increase the X-ray intensity of aluminum detected as secondary X-rays An artificial lattice has been used.

[0003]

However, the artificial lattice cannot disperse only the tungsten Mα (W-Mα) line for excitation of aluminum due to its poor dispersibility, and the silicon lattice has a silicon Kα (Si-Kα). X-rays that excite the rays, for example, part of W-Mβ rays and even high-energy X-rays are also separated. Therefore, when analyzing aluminum on a silicon wafer by the total reflection X-ray fluorescence analysis method, aluminum Kα (Al-Kα) to be detected is used.
The line overlapped the base of the Si-Kα line, making it difficult to analyze aluminum.

[0004] In order to solve the above problem in the analysis of aluminum, it is necessary to minimize the amount of Si-Kα radiation which is the background with respect to the Al-Kα radiation which is the detection target. On the other hand, the inventor of the present application has found that by detecting secondary X-rays from a sample through an aluminum filter with a detector, the background Si-Kα rays can be reduced.

[0005] Therefore, the present invention is based on silicon as a main component,
An object of the present invention is to provide a total reflection X-ray fluorescence analysis method and a total reflection X-ray fluorescence spectrometer capable of easily and accurately analyzing aluminum by using the aluminum filter for a sample containing aluminum. It is assumed that.

[0006]

In order to achieve the above object, a total reflection X-ray fluorescence analysis method according to the present invention comprises irradiating a sample to be analyzed containing primary silicon and aluminum with primary X-rays. The method for analyzing a sample by total reflection and detecting secondary X-rays from the sample includes the following steps. First, the secondary X-ray is set to be detected through an aluminum filter, and in this state, a blank sample containing silicon as a main component and not containing aluminum is irradiated with the primary X-ray to generate the secondary X-ray. The filter interference intensity, which is the intensity of aluminum spectral lines, and the blank total, which is the sum of the intensities of secondary X-rays at or above a predetermined energy level for exciting aluminum, are obtained, and the correlation between the blank sum and the filter interference intensity is obtained. Ask for. Next, the sample to be analyzed is irradiated with primary X-rays,
Sample strength, which is the intensity of the aluminum spectral lines,
A sample sum, which is a sum of the intensities of the secondary X-rays at or above the predetermined energy level, is measured. Further, the filter interference intensity is determined from the total value of the blank corresponding to the sample total using the correlation, and the true intensity of the aluminum spectral line is determined by subtracting the filter interference intensity from the sample intensity.

According to this analysis method, the secondary X
Since the lines are detected through an aluminum filter, the background component contained in the sample intensity is reduced. From the sample sum obtained at this time, the filter interference intensity obtained by the correlation between the blank sum and the filter interference intensity corresponds to an excess component that overlaps with the sample intensity when the secondary X-rays excite the aluminum filter. I do. Therefore, by subtracting the filter interference intensity from the sample intensity, excess components due to the excitation of the filter are removed, and accurate aluminum analysis can be performed.

In the above-mentioned total reflection X-ray fluorescence analysis method, for example, the aluminum spectral line is Al-Kα ray and the predetermined energy level is 1.6 KeV. According to this analysis method, a value corresponding to the excess component generated from the aluminum filter excited by the secondary X-ray can be obtained as the filter interference intensity, so that the value of the excess component subtracted from the sample intensity becomes accurate. In addition, the analysis accuracy of aluminum can be further improved.

The total reflection X-ray fluorescence spectrometer of the present invention irradiates primary X-rays from an X-ray source to a sample to be analyzed containing silicon as a main component and containing aluminum and totally reflects the sample, thereby obtaining a secondary sample from the sample. An apparatus for analyzing a sample by detecting X-rays with a detector, wherein the filter is made of aluminum that allows secondary X-rays to pass before entering the detector, a correlation determination unit, a first measurement control unit, and a second measurement unit. It is provided with measurement control means and calculation means.
The correlation determining means irradiates a primary X-ray to a blank sample containing silicon as a main component and not containing aluminum,
The filter interference intensity, which is the intensity of the spectral line of aluminum generated from the filter, and the blank total, which is the sum of the intensities of the secondary X-rays at or above a predetermined energy level for exciting aluminum, are measured. A correlation with the filter interference intensity is obtained. The first measurement control means irradiates the sample to be analyzed with primary X-rays and measures the sample intensity, which is the intensity of aluminum spectral lines. The second measurement control means measures the intensity of the secondary X-rays at or above the predetermined energy level, and obtains a sample sum that is a sum thereof. The calculating means obtains a filter interference intensity from the value of the blank total corresponding to the sample total using the correlation, and obtains a true intensity of the aluminum spectral line by subtracting the filter interference intensity from the sample intensity.

[0010] According to the total reflection X-ray fluorescence spectrometer having the above-described structure, highly accurate aluminum analysis can be performed as in the case of the total reflection X-ray fluorescence analysis method of the present invention.

In this total reflection X-ray fluorescence spectrometer, for example, the aluminum spectral line is Al-Kα ray, and the predetermined energy level is 1.6 KeV.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing a schematic configuration of a total reflection X-ray fluorescence spectrometer according to an embodiment of the present invention. This total reflection X-ray fluorescence spectrometer comprises an X-ray source 3 for generating primary X-rays 5 and a sample stage 6 for fixing samples 7 and 8 (refer to blank sample 7 or analysis target sample 8; the same applies hereinafter).
A detector 10 for detecting secondary X-rays 9 from the samples 7 and 8 irradiated with the primary X-rays 5, and an analyzer 11 for analyzing the aluminum of the samples 7 and 8 based on the output of the detector 10. And A filter 12 made of, for example, a 5 μm-thick aluminum film is attached in front of the window of the detector 10 based on the findings of the inventor of the present application, and the secondary X-rays 9 are passed through the filter 12 to the detector 10. Make it incident.

The X-ray source 3 has an X-ray generator 1 and a spectroscope 2 composed of a spectral crystal or an artificial multilayer film lattice.
The spectroscope 2 converts the X-rays 4 generated from the X-ray generator 1 into a single color, and forms a primary X-ray including, for example, tungsten Mα rays.
The sample 7 and 8 are irradiated as a line 5. Blank sample 7
Is a silicon wafer containing silicon as a main component and not containing aluminum in this example. In this example, the sample 8 to be analyzed is a silicon wafer containing silicon as a main component and containing aluminum.

The analyzer 11 includes a first measurement control means 1
3, a second measurement control unit 14, a correlation determination unit 15, a calculation unit 16, and a memory 17. The first measurement control means 13 is configured to irradiate the primary X-rays 5 and totally reflect, based on the output of the detector 10 for detecting the secondary X-rays 9 from the sample 8 to be analyzed, For example, Al
The intensity of the Kα ray is determined as the sample intensity I _OB . The second measurement control means 14 measures the intensity of the secondary X-ray 9 at a predetermined energy level or higher, for example, 1.6 KeV or higher, and obtains the total as the sample total _{IE, OB} .

[0015] The correlation determination unit 15, the to irradiate the primary X-ray 5 in the blank sample 7, spectral lines of Arumiumu this case, for example, the strength of Al-K [alpha line, causes measured as a filter interference intensity I _F the predetermined Nerugi level (e.g. 1.6KeV) or the intensity of the secondary X-ray 9 in exciting the aluminum filter 12 by measuring, seek blank sum I _E is the sum, and the blank sum I _E determining a correlation between the filter interference intensity I _F as shown in FIG. The filter interference intensity I at this time
_{Since F} takes a different value by changing the irradiation angle of the primary X-rays 5 with respect to the blank sample 7 and changing the amount of the primary X-rays 5 penetrating into the blank sample 7, the filter interference intensity I _F by obtaining the corresponding blank sum I _E respectively, filter the interference intensity I _F - obtaining a plurality of correlation points blank sum I _E, we obtain the correlation line 18, for example by the least squares method. Correlation line 18 thus obtained
Are stored in the memory 17 as a data map.

The calculating means 16 applies the value of the blank sum I _E corresponding to the sample sum I _{E, OB} obtained by the second measuring means 14 to the correlation line 18 to obtain the blank sum I _E.
Indexing filter interference intensity I _F corresponding to, to calculate the true intensity I _REAL of the filter interference intensity I _F a is subtracted from the sample intensity I _OB which has been determined by the first measurement control unit 13 of aluminum spectral line.

The procedure for performing aluminum analysis on the sample 8 to be analyzed by the above-described apparatus will be described below. First, a blank sample 7 is irradiated with primary X-rays 5 and totally reflected,
Based on the output of the detector 10 which detects the line 9, the analyzer 11
Is used to determine the correlation between the filter interference intensity _IF and the blank sum _IE as follows. That is, the measured intensity and a filter interference intensity I _F of Al-K [alpha line, detector 10 secondary X in 1.6KeV than a predetermined energy level to excite the aluminum filter 12 disposed in front of The intensity of the line 9 is measured, and the sum is obtained as a blank sum _IE . Such a measurement of the filter interference intensity _IF and the blank total _IE is performed a plurality of times by changing the incident angle of the primary X-rays 5 irradiating the blank sample 7 to obtain the filter interference intensity _IF
A correlation line 18 between the blank and the blank sum _IE is obtained as shown in FIG. The correlation line 18 is stored in the memory 17 as a data map.

Next, a primary X-ray 5 is irradiated to the sample 8 to be analyzed and totally reflected, and a detector 10 for detecting the secondary X-ray 9 is used.
The intensity of the Al-Kα ray is measured as the sample intensity I _OB by the first measurement control means 13 of the analyzer 11 based on the output of. Also, at this time, the secondary X that is 1.6 KeV or more
The sum of the intensities of the line 9 is obtained by the second measurement control means 14 as the sample sum _{IE, OB} .

Here, since the secondary X-rays 9 are incident on the detector 10 through the aluminum filter 12, the Si-Kα rays which are the background of the sample intensity I _OB are restricted by the filter 12. That is, in this case, the transmittance of the Al-Kα ray in the aluminum filter 12 is 5
While the transmittance slightly decreases to 7.6%, the transmittance of the Si-Kα ray greatly decreases to 0.95%. As a result, the measurement accuracy of the sample strength I _OB is greatly improved as compared with the conventional case. On the other hand, the filter 12 generates the secondary X-ray 9 and the reflection X from the surroundings.
The Al-Kα ray is generated by being excited by the X-ray or the like, and this is included as an excess component in the sample intensity I _OB which is the intensity of the Al-Kα ray from the sample 8 to be analyzed. I _OB is slightly larger than the true sample intensity I _REAL . Exciting the filter 12 to produce Al-K
The α-rays are generated by X-rays having an energy level of 1.6 KeV or more.

The error caused by the secondary X-ray 9 exciting the aluminum filter 12 is analyzed by the analyzer 1.
The correction is performed as follows by the calculation means 16 in 1. Since the blank sample 7 does not contain aluminum, all the Al-Kα rays detected by the detector 10 are:
The filter 12 is generated by being excited by an X-ray of 1.6 KeV or more. Thus, the blank sum I _E is the sum of the X-ray intensity of more than 1.6KeV is associated with the filter interference intensity I _F is the intensity of Al-K [alpha line from the filter 12. Therefore, the relationship is stored as a correlation line 18, and the sum I _{E, OB} of components of 1.6 KeV or more contained in the secondary X-ray 9 from the analysis sample 18 is obtained, and a blank having the same value as this is obtained. Correlation line 18 from sum _IE
The filter interference intensity _IF , that is, the filter 12
From the Al-Kα line intensity (the intensity of the excess component).

The arithmetic means 16 first stores the blank total _IE (in this case, the same) corresponding to the sample total _{IE, OB} obtained by the second measurement control means 14 in the memory 17 first. The corresponding filter interference intensity _IE is obtained by applying the correlation line 18 of FIG. 2 stored as a map. Next, the filter interference intensity _IE is subtracted from the sample intensity _IOB obtained by the first measurement control means 13 to obtain an Al-
The true intensity I _REAL (= I _OB −I _E ) of the Kα ray is obtained. By using such a method, aluminum analysis can be performed with higher accuracy. In fact, Al-
Detection limit of Kα ray intensity, conventionally, those were 10 ¹¹ atoms / cm ² or so, if by this method, 10 ¹⁰ atoms /
It was improved to cm ^2.

To determine the aluminum concentration in the sample 8 to be analyzed from the true intensity I _REAL of the Al-Kα ray thus obtained, the aluminum concentration C and the Al-Kα
A calibration curve 19 as shown in FIG. 3 showing the relationship with the line intensity I _REAL is used. This calibration curve 19 was prepared by preparing several silicon wafers having known aluminum concentrations and different aluminum concentrations as standard samples, and using these standard samples by the above-described total reflection X-ray fluorescence analysis to determine the Al-Kα ray intensity I, respectively. _{Find REAL} and calculate each aluminum concentration C
From the correlation point between the intensity and the Al-Kα ray intensity I _REAL , for example, using the least squares method. Sample 8 to be analyzed
Was determined by the total reflection X-ray fluorescence analysis method.
The aluminum concentration C in the sample 8 to be analyzed can be obtained by applying the 1-Kα ray intensity I _REAL to the calibration curve 19 in FIG. Thereby, highly accurate aluminum analysis can be easily performed.

In FIG. 3, a broken line 20 indicates a calibration curve when total reflection X-ray fluorescence analysis is performed without using the aluminum filter 12. The calibration curve 19 when the filter 12 is used has a lower transmittance than the calibration curve 20 when the filter 12 is not used.
I _REAL is reduced by the amount of the filter.

[0024]

As described above, according to the method for analyzing total reflection X-ray fluorescence or the apparatus for total reflection X-ray fluorescence of the present invention, an aluminum filter is used in the analysis of aluminum of a sample. Since excess components due to the excitation of the filter are removed, aluminum analysis can be performed easily and with high accuracy.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a total reflection X-ray fluorescence spectrometer used in an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an example of a correlation line used in the present invention.

FIG. 3 is a characteristic diagram showing an example of a calibration curve used in the present invention.

[Explanation of symbols]

3: X-ray source, 5: primary X-ray, 7: blank sample, 8: sample to be analyzed, 9: secondary X-ray, 10: detector, 12: aluminum filter, 13: first measurement control means, 14 ...
Second measurement control means, 15 ... correlation determination means, 16 ... calculation means

Claims (4)

[Claims] 1. A total reflection fluorescence X for irradiating primary X-rays to a sample to be analyzed containing silicon as a main component and containing aluminum and totally reflecting the sample, and detecting secondary X-rays from the sample to analyze the sample. In the X-ray analysis method, the secondary X-rays are set to be detected through an aluminum filter, and in that state, a blank sample containing silicon as a main component and not containing aluminum is irradiated with primary X-rays, and The filter interference intensity, which is the intensity of the aluminum spectral lines generated from the laser beam, and the blank total, which is the sum of the intensity of the secondary X-rays at or above a predetermined energy level for exciting aluminum, are measured. Calculating a correlation with intensity, irradiating the sample to be analyzed with primary X-rays, the sample intensity, which is the intensity of aluminum spectral lines, and the predetermined energy A sample sum that is the sum of the intensities of the secondary X-rays at or above the level is measured. From the value of the blank sum corresponding to the sample sum, the filter interference intensity is determined using the correlation, and the sample intensity is determined. A total reflection X-ray fluorescence analysis method, wherein a true intensity of an aluminum spectrum is obtained by subtracting a filter interference intensity. 2. The total reflection X-ray fluorescence analysis method according to claim 1, wherein the aluminum spectral lines are aluminum Kα rays, and the predetermined energy level is 1.6 KeV. 3. A sample to be analyzed containing silicon as a main component and containing aluminum is irradiated with primary X-rays from an X-ray source and totally reflected, and secondary X-rays from the sample are detected by a detector. A total reflection X-ray fluorescence spectrometer for analyzing the following: an aluminum filter that allows the secondary X-rays to pass before entering the detector; and a primary X-ray for a blank sample containing silicon as a main component and not containing aluminum. And the filter interference intensity, which is the intensity of the aluminum spectral lines generated from the filter, and the blank sum, which is the sum of the intensity of the secondary X-rays at or above a predetermined energy level for exciting aluminum, is measured. A correlation determining means for obtaining a correlation between the blank total and the filter interference intensity; and irradiating the sample to be analyzed with primary X-rays to obtain a spectrum line of aluminum. First to measure the sample strength, which is the strength
Measurement control means, second measurement control means for measuring the intensity of the secondary X-rays at or above the predetermined energy level to obtain a sample sum that is the sum thereof, from the blank sum value corresponding to the sample sum, A total reflection X-ray fluorescence spectrometer comprising: calculating means for obtaining a filter interference intensity using the correlation, and subtracting the filter interference intensity from the sample intensity to obtain a true intensity of the aluminum spectral line. 4. The total reflection X-ray fluorescence spectrometer according to claim 3, wherein the spectrum line of aluminum is aluminum Kα ray, and the predetermined energy level is 1.6 KeV.