JP2685722B2 - X-ray analysis method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray analysis method using a semiconductor detector.

[0002]

2. Description of the Related Art For example, in total reflection fluorescent X-ray analysis using a semiconductor detector, a trace amount of a component contained in a sample is mainly analyzed, so that the primary X-ray, that is, X
Excitation X which is the characteristic X-ray of the target material used for the radiation source
The background due to the lines becomes a major obstacle to the analysis,
It is necessary to remove even the low energy side intensity of the excited X-ray. The intensity of the excited X-rays has a skirt on the lower energy side than the peak because some of the electrons generated by the excited X-rays incident on the semiconductor detector escape to the outside of the semiconductor detector, and the signal value decreases. This is because.

[0003]

However, in the conventional technique, the intensity of the excited X-ray on the low energy side is not removed, and highly accurate analysis cannot be performed.

The present invention has been made in view of the above conventional problems, and in an X-ray analysis method using a semiconductor detector, an X-ray which is incident on the semiconductor detector and is not to be measured with high intensity.
It is an object of the present invention to provide an X-ray analysis method capable of obtaining the compensated intensity of secondary X-rays to be measured by subtracting the intensity of rays.

[0005]

In order to achieve the above object, the method according to claim 1 is an X-ray analysis method using a semiconductor detector, which is a standard test in which an element to be analyzed is vapor-deposited in a known amount.
From the measurement intensity of the secondary X-ray of the measurement object generated from the material
By subtracting the intensity corresponding to a known amount, high intensity non-measurement X-rays incident on the semiconductor detector ,
To previously obtain a profile of the intensity relationship to the wavelength of its, by subtracting the amount of profile of the unmeasured X-ray from the measured intensity of the secondary X-ray to be measured generated from the unknown sample containing the analyte element, measured Obtain the compensated intensity of the secondary X-ray of interest. This profile includes the skirt portion due to the electric signal output from the semiconductor detector, although the X-ray of that wavelength is not actually incident. As described above, the method of the present invention is characterized in that the true intensity of the secondary X-ray to be measured is obtained by subtracting the background component that does not depend on the incident X-ray.

[0006]

According to the method of the present invention, the profile of the intensity relationship with respect to the wavelength of the high intensity X-rays of the non-measurement target which is incident on the semiconductor detector is obtained by the standard sample, and the sample of the measurement target is obtained. Since the intensity of the X-ray profile outside the measurement target is subtracted from the intensity of the secondary X-ray of the measurement target generated, the compensated intensity of the secondary X-ray of the measurement target is obtained, so that highly accurate X-ray analysis can be performed. it can.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. First, an outline of the X-ray analysis apparatus used in this example will be described. As shown in FIG. 1, in the X-ray analyzer used in this embodiment, the primary X-rays generated from the X-ray source 21
That is, the characteristic X of the target material used for the X-ray source 21
The samples 9 and 23 are irradiated with the excitation X-rays 22 which are the X-rays, and the secondary X-rays 24 generated from the samples 9 and 23 are incident on the semiconductor detector 25. Then, the incident secondary X-ray 2
The intensity of No. 4 is detected, a signal corresponding to the intensity is input to an analyzer 26 such as a peak value classification circuit, and the intensity of the secondary X-ray 24 is analyzed and measured. Here, as described above, the intensity of the excited X-ray detected by the semiconductor detector 25 has a skirt on the lower energy side than the peak. The reason is that some of the electrons generated by the excited X-rays that have entered the semiconductor detector escape to the outside of the semiconductor detector, which reduces the signal value, which will be described in detail.

FIG. 2 shows a vertical cross section of the semiconductor detector. The semiconductor detector includes a gold thin film 3 forming a P layer, a silicon film 4 forming a P layer and a dead layer, from the side where X-rays 1 and 2 are incident.
It has a silicon layer 5 which is an I layer and is a sensitive layer, a silicon film 6 which is an N layer and is a dead layer, and a gold thin film 7 which is an N layer. A high voltage is applied to the layered gold film 7. When the incident X-ray (detection X-ray) 1 to the semiconductor detector is completely absorbed in the detection effective volume 5 of the semiconductor detector, all the X-ray energy is converted into electron kinetic energy and generated. The electron current becomes a measurable signal as a peak value (minute voltage) by the electronic circuit connected to the semiconductor detector (complete charge collection effect).

However, when the incident X-rays 2 are absorbed near the detector semiconductor surface 3, the electrons generated secondarily have a detector effective volume in the direction opposite to the direction in which the X-rays 2 are incident. The secondary electrons that may travel outside and have elastic and inelastic confusion effects, and the energy of the electrons decreases while undergoing a complicated process. Will increase. As a result of the generation of this incomplete charge collection effect, the peak value distribution has a skirt on the low energy side. This means that the lower the energy level of the X-ray 2 that is not the measurement target, the stronger the X-ray intensity of the skirt on the low energy side, and the X-ray of the measurement target is at the same energy level as the skirt. If present, this skirt has a greater effect of the error on the measurement intensity.

Here, the tail of the intensity of the excited X-rays is formed on the lower energy side than the peak, in FIG. 1, Compton scattered rays and Rayleigh scattering generated from the samples 9 and 23 irradiated with the excited X-rays 22. Line 24 is semiconductor detector 25
It is thought that this is because it is incident on, but this effect is insignificant. In order to confirm this, instead of the X-ray tube 21 and the samples 9 and 23, ⁵⁵ Fe, which is a radioactive isotope that generates Mn-Kα and Mn-Kβ rays without generating Compton scattering rays or Rayleigh scattering rays, is used ^. As the X-ray source, when the intensity of Mn-Kα rays was detected by the semiconductor detector 25, as shown in FIG. 3, the X-ray tube 21 (FIG. 1) and the samples 9 and 2 were detected.
3 resulted skirt 8 to the low-energy side than the energy that indicates a peak value i _p as in the case with (Figure 1).

In this embodiment, a standard sample 9 shown in a vertical section in FIG. 4 is used in order to remove the intensity of the skirt on the low energy side from the peak of the excited X-ray. For example, in FIG. 1, Z generated from zinc in a silicon wafer, which is an unknown sample 23, by using W-Lβ rays 22 as excitation X-rays 22.
When it is desired to measure the intensity i of the n-Kα ray 24, a standard sample 9 in which a known amount of zinc 11 is vapor-deposited on a silicon wafer 10 is prepared as shown in FIG. And as shown in FIG.
The standard measures the intensity I _m of the sample 9 Zn -Kα rays generated from subtracting the true intensity I known in which Zn -Keiarufa line from the intensity I _m, the W-L? Line is an excitation X-ray The strength I _b of the skirt is obtained.

[0012] Next, as shown in FIG. 6, by measuring the intensity i _m of Zn -Keiarufa rays generated from the unknown sample, the intensity i _m
Then, the true intensity i of the Zn-Kα ray generated from the unknown sample is obtained by subtracting the intensity I _b of the skirt of the W-Lβ ray obtained from the above. For elements other than zinc, if a standard sample is prepared in the same manner and the intensity of the skirt of the W-Lβ line at the energy corresponding to the characteristic X-ray of that element is determined, the element of that element generated from the unknown sample The true intensity of the characteristic X-ray is required. In this embodiment, tungsten is used as the target material of the X-ray tube 21 in FIG. 1 and W-Lβ rays are generated as the excited X-rays 22, but gold is used as the target material and Au is used as the excited X-rays 22. -Lβ
It is also possible to generate an X-ray or Mo-Lα ray as the excited X-ray 22 by using molybdenum as a target material.

The present invention differs from a general X-ray analysis method in which the intensity of X-rays forming a background component incident on the detector is subtracted from the intensity of X-rays of the measurement target. It is characterized in that the electric signal (corresponding to the intensity) output from the detector 25 and corresponding to the background component is subtracted from the intensity of the X-ray even though it is not incident on the semiconductor detector 25.

In the X-ray analyzer utilizing the present invention, the intensity I _b of the skirt as the background obtained as described above is stored in the memory, and the skirt of the skirt is calculated from the measurement data of the unknown sample by the calculator. Data processing is automatically performed by subtracting the intensity I _b . As a result, highly accurate X-ray analysis can be performed quickly.

As described above, in the present embodiment, the profile of the intensity relationship with respect to the wavelength of the excitation X-rays incident on the semiconductor detector is obtained by using the standard sample.
Since the intensity of the profile of the excitation X-ray is subtracted from the intensity of the secondary X-ray of the measurement target generated from the unknown sample to obtain the compensated intensity of the secondary X-ray of the measurement target, the X-ray with high accuracy is obtained.
Line analysis is possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an X-ray analyzer used in this example.

FIG. 2 is a vertical sectional view of a semiconductor detector.

FIG. 3 is a diagram showing the intensity of Mn-Kα rays detected by a semiconductor detector using ⁵⁵ Fe, which is a radioactive isotope, as an X-ray source.

FIG. 4 is a vertical cross-sectional view of a standard sample used in this example.

FIG. 5 is a diagram showing the intensity of a skirt of a W-Lβ line which is an excited X-ray obtained by using a standard sample in this example.

FIG. 6 is a diagram showing the true intensity of Zn-Kα rays generated from an unknown sample obtained in this example.

[Explanation of symbols]

9 ... standard sample, 23 ... sample to be measured, 25 ... semiconductor detector, I _b ... strength unmeasured X-ray, i _m ... intensity of the secondary X-ray to be measured, i ... second measurement target X-ray compensated intensity.

Claims (1)

(57) [Claims] 1. An X-ray analysis method using a semiconductor detector, wherein an element to be analyzed is generated from a standard sample on which a known amount is vapor-deposited.
From the measured intensity of the secondary X-rays to be measured, it corresponds to the known amount.
That by subtracting the intensity, the unmeasured high-intensity X-rays to be incident on the semiconductor detector, to previously obtain a profile of the intensity relationship to the wavelength of its, measured generated from the unknown sample containing the analyte element Of 2
An X-ray analysis method, wherein the compensated intensity of the secondary X-ray of the measurement target is obtained by subtracting the profile of the X-ray outside the measurement target from the measurement intensity of the next X-ray.