JPH01219549A - Fluorescent x-ray analyzer - Google Patents

Abstract

PURPOSE:To increase the fluorescent X-rays from the atoms. in a sample thin film and to increase a fluorescent X-ray detection sensitivity by using a holder which utilizes multilayered thin films alternately laminated with heavy element layers and light element layers as a sample holder on which the sample thin film is installed or formed. CONSTITUTION:The multilayered thin films 10 formed by using, for example, W as a heavy element and C as a light element and alternately laminating 20 times the W layers to about 33A thickness and the C layers to about 54A are formed. The reflectivity can be made to about >=80% with such thin films 10 if the incident X-rays are set at a specific angle. Namely, the X-rays 3 passes the sample 8 and thereafter, about 80% thereof is reflected by the thin films 10 when the thin films 10 are used as the sample holder 9. This reflected X-rays again enter the sample 8. In addition, the incident angle 5 is several times - several tens times the total reflection angle (about 0.05-0.1) and, therefore, the density of the X-rays are several times - several 10 times larger than in the case of the total reflection. Since about 80% of the X-rays 3 emit at the same diffraction angle 6 as the incident angle 5, the quantity of the scattered X-rays intruding into a detector 13 decrease by 70-80% as compared to the case of using the ordinary sample holder. The detection sensitivity is thus improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention uses X-rays or synchrotron radiation to detect trace amounts of elements or ultrathin films with a thickness of several 1Oλ to several 100s, using X-rays or synchrotron radiation. The present invention relates to a fluorescent X-ray analyzer that non-destructively analyzes trace amounts of elements inside.

(Prior art) Conventional fluorescent X-ray analyzers emit X-rays at a distance of 60" from the sample surface.
The incident X-rays generate fluorescent X-rays unique to the elements in the sample, and by detecting these, the constituent elements of the sample are revealed. However, in this case, the X-rays penetrate 2 to 3 μm into the sample, so the number of
Detecting trace elements in an ultra-thin film with a thickness two to three orders of magnitude smaller than the X-ray penetration depth for 0 to several 100 people means that most of the fluorescent X-rays come from sources other than the ultra-thin film of interest. Become,
Since the background is too high, it is extremely difficult to detect, and the detection amount is limited to several tens of ppI11 to several 11,000 pp. Adheres to the sample pole surface or has a thickness of several tens of
To analyze trace elements in ultra-thin human membranes, the best way to analyze them is to use total internal reflection of X-rays, in which only a few dozen X-rays penetrate into the sample.
It was more effective than ordinary fluorescent X-ray analysis. However, X
For linear total internal reflection, the X-ray incident angle used is usually 0.05 to 0.1.
Since the area of the X-ray beam is on the order of degrees, the irradiation area of the X-ray beam expands and the intensity per unit area becomes weaker. Furthermore, since the X-ray beam spreads too much, only a portion of the X-ray beam is incident on the sample.

In addition, since fluorescent X-rays from a sample are emitted from the entire irradiation surface, in the case of a sample with a surface shape of several tens of square meters,
Using a detector with a detection window of about 1 inch in diameter, it is possible to receive all of the generated fluorescent X-rays with the detector.
This is not possible if the detector window becomes smaller than the sample geometry. For example, when the X-ray beam shape is 1 mm long x 10 mm wide and the sample is irradiated at an angle of 0.05°, the shape of the irradiated surface is 1146 mm x 10+11111. Usually, the sample has a length of several mm to several tens of mm, so most of the X-rays are irradiated to areas other than the sample surface.

That is, the amount of fluorescent X-rays generated from the sample is small, and the detection efficiency is also poor due to the limited size of the detection window of the detector.

Furthermore, when total internal reflection X-rays are used, the X-rays penetrate only about 50 people, so elemental analysis of samples with a thickness of about 50 people or more will be less accurate. Currently, X at the laboratory level
The detection sensitivity for heavy elements is only about several thousand ppb with the radiograph. Another method for analyzing trace elements is secondary ion mass spectrometry, which has a maximum detection sensitivity of several tons depending on the sample.
Although some samples reach oppb, this method has the disadvantage that the sample is destroyed.

(Problems to be Solved by the Invention) The present invention efficiently utilizes incident X-rays to generate fluorescent X-rays, and reduces the amount of scattered X-rays that enter the fluorescent X-ray detector. An object of the present invention is to provide a fluorescent X-ray analyzer that enables increased fluorescent X-ray detection sensitivity.

(Means for Solving the Problems) The X-ray fluorescence analyzer of the present invention uses a holder that utilizes a multilayer thin film in which heavy element layers and light element layers are alternately laminated as a sample holder on which a sample thin film is installed or formed. .

Conventional sample holders use single materials such as single metals, alloys, glass, etc., and do not use laminated layers of different materials.

FIG. 2 shows a schematic diagram of the structure of the multilayer thin film. In FIG. 2, ■ is a heavy element layer, and 2 is a light element layer.

When this multilayer thin film is irradiated with X-rays, Brang's equation (2
X-rays are diffracted according to d sin θ-λ (where d is the thickness of each of the heavy element layer and light element layer, θ is the incident angle, and λ is the wavelength of the X-ray). The principle of this diffraction is shown in FIG. In FIG. 3, 3 indicates the incident X-ray, 4 indicates the diffracted X-ray, 5 indicates the X-ray incident angle, and 6 indicates the X-ray diffraction angle. Further, FIG. 4 shows an example of an X-ray diffraction profile from a multilayer thin film. The vertical axis is the diffracted X-ray intensity I and the incident X-ray intensity I. The X-ray intensity is expressed as a ratio of , and the horizontal axis is the diffraction angle.

This is a diffraction profile from a multilayer thin film in which W (tungsten) is a heavy element and C (carbon) is a light element, and the W layer is approximately 33 thick and the 0 layer is alternately laminated 20 times with a thickness of approximately 54 thick.

In this way, in a multilayer thin film, if the incident X-ray is set at a certain specific angle, it is possible to increase the reflectance to about 80% or more. That is, when a multilayer thin film is used as a sample holder, incident X-rays pass through the sample and are reflected by the multilayer thin film by about 80%, and the reflected X-rays enter the sample again. In other words, the amount of X-rays before being reflected on this sample is I. If so, the actual X-ray incident on the sample reaches about 1.81o. Moreover, the incident angle is several times the total reflection angle (about 0.05° to 0.1 layer)
Since the density of the incident X-ray is several tens of times higher, there is an advantage that the density of incident X-rays is several times to several tens of times higher than that in the case of total internal reflection.

In addition, approximately 80% of incident X-rays exit at the same diffraction angle as the incident angle, so the amount of X-rays that enter the detector, that is, the amount of scattered It is reduced by 70-80% and the detection sensitivity is improved. Therefore, it becomes possible to detect trace substances with high sensitivity.

FIG. 1 is a configuration diagram of the fluorescent X-ray analyzer of the present invention,
3 represents the incident X-ray, 4 represents the diffracted X-ray, 5 represents the X-ray incident angle, and 6 represents the X-ray diffraction angle. 7 is an X-ray source, 8 is a sample, 9 is a multilayer thin film holder, 10 is a multilayer thin film, 11 is a multilayer thin film holder, 12 is a generated fluorescent X-ray, 13 is a semiconductor detector,
14 is a measurement circuit.

(Example) A fluorescent X-ray analyzer having the configuration shown in FIG. 1 was used. The X-ray generation voltage and current are 50 V and 300 mA, respectively. The multilayer "A" film holder used has the X-ray reflection characteristics shown in Figure 4.This multilayer thin film holder is made by laminating 40 layers of W and 0 layers alternately on Si with a thickness of about 16 and 24, respectively. It was made by

The intensity of the first-order diffraction peak is the intensity of the incident X-ray I. It was 73% of the total. Therefore, the angle at which this peak appears 2θ=2.
At 2 degrees, the sample will be irradiated with X-rays approximately 1.7 times as large as the incident X-rays II O. 50mmX 20mm
A Nbl film sample with a thickness of about 100 people with a surface shape of
It was formed on this multilayer thin film holder by sputtering and analyzed at an X-ray incident angle of 2θ=2.2 degrees. At this time, since the X-ray irradiation area was approximately 1722 in the case of using total internal reflection, the irradiation density was approximately 22 times higher. Moreover, the amount of X-rays incident on the sample is I. The ratio 1os/Io of 3 to the irradiated X-ray I0 was about 19 times that of the total internal reflection method in the method of the present invention. Approximately 30% of the incident X-ray dose affects the background, but due to a significant increase in 1 os/I0, the detection sensitivity is
Improved by orders of magnitude. This analysis revealed that the sample contained approximately 6 Zn.
50 ppb was detected. This value was comparable to the value of about 570 ppb obtained by destructive analysis of the same sample using a secondary ion mass spectrometer.

(Effects of the Invention) As explained above, the X-ray fluorescence analyzer of the present invention can increase the amount of X-rays incident on the sample compared to the X-ray fluorescence analyzer that uses total internal reflection. Since it is possible to increase the amount of fluorescent X-rays from atoms, and the background is significantly reduced compared to ordinary fluorescent X-ray analyzers, non-destructive and highly sensitive trace substance analysis becomes possible.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the fluorescent X-ray analyzer used in the examples of the present invention, Figure 2 is a schematic diagram of the structure of a multilayer thin film, Figure 3 is a diagram of the principle of X-ray diffraction using a multilayer thin film, and Figure 4 FIG. 2 is a diagram showing an example of an X-ray diffraction profile by a multilayer thin film. 1...Heavy element layer 2...Light element layer 3...
- Incident X-ray 4... Diffraction X-ray 5... X-ray incident angle 6... X-ray diffraction angle 7... X-ray source 8... Sample thin film 9... Multilayer thin film holder 10...・Multilayer thin film 11... Multilayer thin film holding stand 12... Fluorescent X-rays generated 13... Semiconductor detector 14... Measurement circuit Figure 1 f4 - Measurement circuit Figure 2 Figure 3 Figure 4 ↑Angle forgery θ(A) Procedure amendment Written March 29, 1988 Kunio Ogawa, Director General of the Patent Office 1, Indication of the case Patent Application No. 44210 of 1988 2, Name of the invention Fluorescent X-ray analysis Apparatus 3, Relationship with the case of the person making the amendment Patent applicant (422) Nippon Telegraph and Telephone Corporation 4, agent (1) The scope of claims in line 1 to line 1O of the specification tube is as follows: correct. "2. Claim 1: Irradiation with X-rays generated from an X-ray source, and as a result,
In a fluorescent X-ray analyzer that analyzes trace elements in a sample by detecting fluorescent X-rays generated from the sample with a detector, a sample holder for installing or forming a sample thin film is composed of a multilayer thin film and a multilayer thin film holder. A fluorescent X-ray spectrometer characterized by using a holder.

Claims (1)

[Claims] 1. In an X-ray fluorescence analyzer that irradiates a sample with X-rays generated from an X-ray source and then detects the fluorescent X-rays generated from the sample with a detector to analyze trace elements in the sample, A fluorescent X-ray apparatus characterized in that a holder consisting of a multilayer thin film and a multilayer thin film holder is used as a sample holder for installing or forming a holder.