JP2022013497A - X-ray analysis device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a method of continuously measuring a large number of small pieces in a fluorescent X-ray analyzer by eliminating a position adjusting mechanism and a position adjusting process for arranging a sample in a primary X-ray X1 irradiation region and realizing a simple configuration. To do.
SOLUTION: An X-ray irradiation unit capable of irradiating a sample with X-rays, an X-ray detection unit for detecting secondary X-rays generated from the sample, a sample transfer unit for transporting a sample, and a detected X-ray intensity. A fluorescent X-ray analyzer is configured including a data processing unit to be processed, and each component is provided with the following functions. The sample transfer unit moves the sample so that the sample passes through the X-ray irradiation position. The X-ray detector continuously acquires the X-ray spectrum at a time interval shorter than the time required for the sample to pass through the X-ray irradiation unit. The data processing unit selects the spectrum at the time when the sample is in the X-ray irradiation unit from the continuously acquired array of X-ray spectra based on the characteristics of the X-ray spectrum.
[Selection diagram] Fig. 1

Description

The present invention relates to a fluorescent X-ray analyzer for measuring the composition of a sample and the film thickness of a coating.

X-ray fluorescence analysis is a method of exciting an element contained in a sample by irradiating the sample with X-rays and analyzing characteristic X-rays peculiar to the element emitted as a result. Since the obtained fluorescent X-ray spectrum contains information related to the large amount and low amount of elements present in the region irradiated with X-rays, the composition ratio of the sample and the multilayer can be obtained by analyzing the spectrum with an appropriate model. The film thickness of the structure can be obtained. Since these analysis processes are often performed in a non-destructive and non-contact manner, they may be used for quality control of industrial products such as plating film thickness tests defined by JIS H8501.

From the principle of fluorescent X-ray analysis, the area irradiated with X-rays is the analysis target area. Therefore, it is possible to appropriately limit the irradiation diameter of the X-ray to be irradiated according to the size of the measurement area and to acquire the fluorescent X-ray spectrum in a state where the measurement target site is correctly arranged in the X-ray irradiation area. You will need it.

As a fluorescent X-ray analyzer that acquires a fluorescent X-ray spectrum when the target area is correctly irradiated with X-rays, the sample to be measured is placed on a sample stage that can be driven in two or three orthogonal axes, and the sample is sampled. After adjusting the position of the sample so that the measurement site of the above is placed at the X-ray irradiation position, the measurement is performed with the sample stationary. At this time, it is also widely practiced to provide an optical system in which the X-ray irradiation position is focused on the center of the field of view and the sample is observed by optical means, and the sample is adjusted to the X-ray irradiation position by using the optical system. (See Patent Document 1)

In the case of a fluorescent X-ray analyzer that measures the thickness of the coating on the surface of a long sheet-shaped sample, the measurement is performed while continuously feeding the sample so as to pass through the X-ray irradiation position, and the measurement time. In some cases, the analysis is performed as the average information of the X-ray irradiation position and the area on the passed line. Compared with the above-mentioned method of adjusting the sample position and measuring in a stationary state, it is possible to efficiently inspect many parts because the time for adjusting the sample position is not required.

However, this method can be applied when the measurement target is continuously distributed over a long sample, and cannot be applied when a large number of small pieces of sample are sent intermittently.
Therefore, we have improved the efficiency of measurement by automatically detecting a large number of samples placed on the sample stage by automating the position adjustment.

There are several approaches to automatic sample position adjustment, one of which is based on an optical sample observation image. As described above, an optical sample observation means is provided, and the deviation between the irradiation position and the sample is detected by using image processing technology such as pattern matching on the sample image obtained there, and the sample stage is controlled according to the deviation amount. The sample is placed at the X-ray irradiation position.

This first approach assumes that the image of the optical sample observation means coincides with the X-ray irradiation position or that the relative positions of the axes are known accurately. However, these relative positional relationships may shift due to various factors such as changes over time and thermal expansion. The smaller the measurement target, the more the influence of the deviation between the observation optical axis and the X-ray irradiation axis cannot be ignored.

In such a case, as a second approach, a method of correcting the sample position using the relationship between the stage coordinates and the X-ray intensity is disclosed in Patent Document 2.

Japanese Unexamined Patent Publication No. 06-273147 Japanese Unexamined Patent Publication No. 06-273146

In the above-mentioned conventional technique, the position of the sample is adjusted and the sample is measured in a stationary state, and since there is time required for adjusting the position of the sample, there is a problem in inspecting a large number of samples in a short time. there were. In addition, a high-definition sample observation optical system and a high-precision multi-axis sample stage are required, which causes a problem that the measurement system becomes expensive.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an X-ray analyzer capable of continuously measuring a large number of small samples without stopping them.

In order to solve the above problems, in the present invention, an X-ray irradiation unit that irradiates a sample with X-rays, an X-ray detection unit that detects secondary X-rays generated from the sample, and a sample transport unit that transports the sample. , An analyzer that continuously acquires the X-ray spectrum of the secondary X-rays detected by the X-ray detector at intervals shorter than the time required for the sample to pass through the X-ray irradiation unit. Whether or not the sample moving in the sample carrier has passed the X-ray irradiation position from the secondary X-ray intensity of the energy of a specific element in the spectrum obtained by the instrument and the set X-ray intensity threshold. It is an X-ray analyzer characterized by determining.

In the X-ray analyzer of the present invention, the data processing unit compares the threshold value of the X-ray intensity set by the X-ray intensity of the energy of a specific element of the sample, and determines whether or not the sample is in the X-ray irradiation unit. It is characterized by making a judgment.

In the X-ray analyzer of the present invention, the data processing unit compares the X-ray intensity threshold set by the X-ray intensity of the energy of a specific element of the material of the surface of the sample transporting unit, and the sample becomes the X-ray irradiation unit. It is characterized by determining whether or not it exists.

The X-ray analyzer of the present invention compares the X-ray intensity of the scattered radiation of the primary X-ray with the threshold value of the X-ray intensity set by the data processing unit, and determines whether or not the sample is in the X-ray irradiation unit. It is characterized by doing.

The fifth aspect of the present invention for solving the above-mentioned problems is the first aspect, in which the data processing unit uses the spectral features obtained by machine learning to determine the spectrum at the time when the sample is in the X-ray irradiation unit. Is to select.

The sixth aspect of the present invention for solving the above-mentioned problems is to use the X-ray spectrum obtained by the histogram of the X-ray count in which the range of continuous energy or wavelength is divided at equal intervals in the first to fifth aspects. be.

A seventh aspect of the present invention for solving the above problems is to use a count of a specific energy range or an X-ray spectrum formed by a plurality of unions thereof in the first to fifth aspects.

According to the present invention, an X-ray irradiation unit capable of irradiating a sample with X-rays, an X-ray detection unit for detecting secondary X-rays generated from the sample, a sample transfer unit for transporting the sample, and the detected X-ray intensity can be determined. The fluorescent X-ray analyzer can be calibrated by the data processing unit to be processed, and the position adjustment mechanism and the position adjustment process for arranging the sample in the primary X-ray irradiation region can be eliminated, and a simple configuration can be realized.

In the embodiment of the fluorescent X-ray apparatus according to the present invention, it is the schematic whole block diagram which shows the X-ray apparatus in the state which the primary X-ray is not irradiating a sample. It is a figure which shows the spectrum in the state which the primary X-ray is not irradiating a sample. In the embodiment of the fluorescent X-ray apparatus according to the present invention, it is the schematic whole block diagram which shows the X-ray apparatus in the state which the primary X-ray irradiates a sample. It is a figure which shows the spectrum of the state which the primary X-ray irradiates a sample. It is a figure which shows the spectrum measured continuously at a predetermined time interval while transporting a sample. It is a figure which shows the spectrum when the sample transport part is plastic. It is a spectral diagram which shows the energy by the channel which divided by the equal interval ΔE.

Hereinafter, embodiments of the X-ray analyzer according to the present invention will be described with reference to the drawings.

The X-ray analyzer of the present embodiment includes a sample transport unit 3 on which the sample S is placed and can be moved in the transport direction D, an X-ray irradiation unit 1 that irradiates the sample S with primary X-rays X1, and a sample. Detects secondary X-rays such as scattered X-rays and fluorescent X-rays generated from the sample S irradiated with the primary X-ray X1 and the primary X-ray adjusting means 4 for forming the irradiation diameter of the primary X-ray X1 to be irradiated to. The sample S includes an X-ray detection unit 2, an analyzer 5 connected to the X-ray detector 2 to analyze the signal of energy information of the secondary X-rays, and a data processing unit 7 connected to the analyzer 5. Is not at the irradiation position 6, which is shown in FIG.
Further, the case where the sample S is at the irradiation position 6 is shown in FIG.

An X-ray tube is used as the X-ray irradiation unit 1 for irradiating the sample S with the primary X-ray X1. The X-ray tube is housed in a housing with proper insulation of the high voltage applied, a cooling mechanism to dissipate the heat generated, and a shield of X-rays in unnecessary directions for safety. The primary X-ray adjusting means 4 is, for example, a collimator having pores in a material such as tungsten or brass having a sufficiently large X-ray shielding ability, or an X such as a polycapillary or a monocapillary that utilizes the total reflection phenomenon of the inner surface of a hollow glass tube. A line condensing element can be used. The irradiation diameter formed by the primary X-ray adjusting means 4 is determined based on the size of the sample S and the transport speed of the sample transport unit 3 on which the sample S is placed and can be moved in the transport direction D. If the arrangement of the sample S in the direction orthogonal to the transport direction D cannot be ignored with respect to the size of the sample, the irradiation diameter is determined in consideration of the deviation amount. As an example, the irradiation diameter is set to the extent that the expected amount of misalignment is subtracted from the size of the sample. As a result, all the fluorescent X-rays generated when the sample is in the irradiation position can be practically regarded as being from the sample.

The sample transport unit 3 is a belt conveyor in which an endless belt is wound around a pair of rollers, and the sample S can be continuously transported by placing the sample S and moving it relative to a predetermined scanning direction. The surface material of the sample transport unit 3 on which the sample S is placed is selected so that the energy of the secondary X-rays generated from the sample S does not interfere with the energy of the secondary X-rays generated from the surface of the sample transport unit 3. For example, when the sample S is composed of copper (Cu) or nickel (Ni), aluminum (Al) is used as the surface material of the sample transport unit 3. The sample transport unit 3 is arranged so that the locus of movement of the mounted sample S passes through the irradiation position 6 where the primary X-ray X1 is irradiated.

Here, the arrangement of the sample is regulated in consideration of the irradiation diameter of the primary X-ray X1 in the direction orthogonal to the transport direction D of the sample, but the arrangement of the sample with respect to the transport direction D, that is, the individual sample S is transported. The minimum interval is such that the measurement in the absence of at least one sample is sandwiched between two consecutive samples, and if the interval is larger than the interval, there is no limitation and the interval does not have to be equal. The shape of the sample transfer unit 3 is not limited to a disk shape or the like other than the belt conveyor, and the trajectory of the sample transfer intersects with the primary X-ray X1.
It should be noted that the number of samples to be transported may be one.

The X-ray detector 2 uses an energy-dispersed X-ray detector such as a semiconductor detector or a proportional counter. This generates an electric charge proportional to the energy of one incident X-ray photon, converts it into a voltage signal proportional to the amount of the electric charge, further AD-converts it, and outputs it as a digital value.
A wavelength dispersive X-ray detector may be used as the X-ray detector.

The analyzer 5 is connected to the X-ray detector 2 to analyze the signal. The analyzer 5 is, for example, a wave height analyzer (multi-channel analyzer) that obtains the wave height of a voltage pulse from the above signal and generates an energy spectrum. The analyzer 5 discriminates the X-ray photon signal output from the X-ray detector 2 for each energy, counts the number of incidents for each energy, and obtains a spectrum as the X-ray intensity.

In FIG. 7, the analyzer 5 discriminates for each energy, counts the number of incidents for each energy, arranges a plurality of channels 42 in which the energy of the spectrum is divided into equal intervals ΔE as X-ray intensity, and counts for each channel 42. It is expressed as an array of. The time Tm for accumulating the incident count is set so as to be the following mathematical formula 1.

Here, L is the length of the measurement target portion on the sample S in the transport direction D, and V is the transport speed of the sample S. Here, as an example, Tm is set to 1/10 of L / V.
It is desirable that the time Tm for accumulating the incident count is shorter than the time required for the sample to pass through the X-ray irradiation unit.

This spectrum integration operation is continuously performed, and the obtained spectrum is stored in the memory of the data processing unit 7 as an array of spectra. From the obtained spectrum and the set threshold value, the data processing unit 7 determines whether or not the sample S moving in the sample transport unit 3 has passed through the irradiation position 6.
Further, the spectra stored in the memory of the data processing unit 7 are overwritten in the order of oldest to prevent the storage area from being saturated, but by mounting the memory so that the number of spectra that can be written at one time is sufficiently large, later To prevent the next spectrum from being overwritten within the time required for processing.

The analyzer 5 is a wave height analyzer (multi-channel pulse height analyzer) that obtains the wave height of a voltage pulse from a signal from the X-ray detection unit 2 and generates an energy spectrum.
The data processing unit 7 monitors the spectra acquired sequentially and detects changes in the spectra due to the presence or absence of the sample S.

The case where the main component of the material of the sample transport unit 3 contains the element A and the sample S contains the element B as the main component will be described. FIG. 2 shows the spectrum 10 when the sample S is not at the irradiation position 6 as shown in FIG. 1 and the horizontal axis is energy and the vertical axis is X-ray intensity. Since the surface of the sample transport unit 3 is located at the irradiation position 6, the spectrum 10 has an X-ray intensity peak at the energy 11 of the fluorescent X-ray of the element A, which is the main component of the material of the sample transport unit 3. Next, FIG. 4 shows the spectrum 12 when the sample S is at the irradiation position 6 as shown in FIG. Since the sample S is at the irradiation position 6, the energy 13 of the fluorescent X-ray of the element B, which is the main component of the sample S, has a peak of X-ray intensity. At this time, the X-ray intensity of the energy 11 of the fluorescent X-ray of the element A in FIG. 4 is smaller than that in FIG.
Utilizing this property, a predetermined X-ray intensity threshold value 14 is provided, and when the X-ray intensity of the fluorescent X-ray energy 13 of the element B, which is the main component of the sample S, exceeds the threshold value 14, the sample S is irradiated. It is determined that it exists at the position 6.

In this embodiment, since Tm is set to 1/10 of L / V as described above, as shown in FIG. 5, the spectrum T1 is continuously measured at predetermined time intervals while transporting the sample S. T21 is shown from.
In the case of FIG. 5, in the spectra T2 to T20, since the X-ray intensity of the fluorescent X-ray energy 13 of the element B is larger than the threshold value 14, it is determined that the sample S is at the irradiation position 6. The determined X-ray intensity of energy 13 is analyzed as the measurement spectrum of the sample. All of these continuous measurement spectra are treated as individual spectra. Alternatively, the first and last measurement spectra such as the spectra T2 and T20 may be excluded, and T3 to T29 may be integrated or averaged and treated as one spectrum. Alternatively, the center or center of gravity of the continuous measurement spectrum may be selected as the spectrum of the sample.

In the X-ray analyzer of the present embodiment, whether or not the sample S is present at the irradiation position 6 is determined by the X-ray intensity of the fluorescent X-ray energy 13 of the element B, which is the main component of the sample S. The presence or absence of a sample may be determined by using the X-ray intensity and a specific threshold value for the energy of fluorescent X-rays whose main component of the material of the sample carrier is element A.
The threshold value at this time may be different from the threshold value of the present embodiment.
As shown in FIGS. 2 and 4, the X-ray intensity of the fluorescent X-ray energy 11 of the element A, which is the material of the sample transport unit 3, also changes depending on the position of the sample S. When the sample S is located at the irradiation position 6, the amount of the primary X-ray X1 irradiated to the sample transport unit 3 is attenuated, and the X-ray intensity of the energy 11 of the fluorescent X-ray of the element A is significantly attenuated. By setting a specific threshold value of the element A, the X-ray intensity of the energy 11 of the fluorescent X-ray of the element A may be compared with this threshold value to determine whether or not the sample S is at the irradiation position 6. ..

Further, in another X-ray analyzer of the present embodiment, when the surface of the sample transport unit 3 is a plastic material, the plastic has a high efficiency of scattering primary X-rays, and in addition, carbon and oxygen which are the main components of the plastic are used. Fluorescent X-ray peaks are rarely detected. Therefore, when the sample S is not at the irradiation position 6, as shown in the spectrum 15 of FIG. 6, the scattering is remarkably wider than the fluorescent X-ray peak, which reflects the continuous X-ray component from the X-ray tube. It becomes a spectrum of lines. Utilizing this property, the X-ray intensity of the energy region 16 in which the intensity of scattered rays is remarkable and does not interfere with the energy 13 of the element B, which is the main component of the sample S, falls below the threshold value 17, so that the sample S is placed at the irradiation position. It may be determined whether or not it is the spectrum in the case of 6.

Further, in another X-ray analyzer of the present embodiment, the material of the sample transport unit 3 cannot be selected so that the material of the sample S and the fluorescent X-ray do not interfere with each other, or the component of the sample S is not stable and an appropriate threshold value is obtained. The case where it is difficult to set is described. As a preparatory step, a large number of spectra are acquired without mounting the sample S, and then a spectrum in which the sample is placed at or near the irradiation position is acquired.
If spectral differences between samples are predicted due to individual differences in samples other than variations in the measurement system, such as variations in sample components and coating thickness, a large number of samples that appropriately reflect variations in individual differences between samples. Care should be taken to include the spectrum. The difference between the spectra of these two groups is learned by deep learning. Using the learning results obtained in the preparatory steps up to this point, it is determined whether or not the sample S has a spectrum when it is at the irradiation position 6.

As shown in FIG. 7, the spectrum generated by the X-ray detector 2 was an array of counts for each energy range divided at equal intervals. In this case, the X-ray intensity of the energy 11 of the fluorescent X-ray whose main component of the material of the sample carrier is element _A is given as the sum of the counts of the channels between the energies _EA0 and EA1. Similarly, the X-ray intensity of the X-ray energy 13 of the element B whose main component is the sample S is also given as the sum of the counts of the channels between the energies _EB0 and _EB1 . This technique makes sense when the peak shape of the spectrum is important in later data processing, but in later data processing the fluorescent X-ray intensity of each element is between _EA0 and _{EA1 and EB0 .} If only the sum of the counts between 1 and _EB1 is sufficient, it is not necessary to divide the channels at equal intervals and generate a spectrum. In such a case, the object of the present invention is achieved by setting the energy region containing the energy peak of the required element as several channels and operating as a plurality of single channel analyzers without dividing the channels at equal intervals. can.

1 X-ray irradiation unit 2 X-ray detection unit 3 Sample transfer unit 4 Primary X-ray adjustment means 5 Analyzer 6 Irradiation position 7 Data processing unit X1 Primary X-ray X2 Secondary X-ray D Sample transfer direction

Claims (8)

An X-ray source that can irradiate the sample with X-rays,
An X-ray detector that detects secondary X-rays generated from the sample,
An analyzer that discriminates the signal output from the sample transport unit that transports the sample and the X-ray detection unit for each energy, counts the number of incidents for each energy, and obtains a spectrum as the X-ray intensity.
The sample moving in the sample transport section passes through the X-ray irradiation position from the secondary X-ray intensity of the energy of a specific element in the spectrum obtained by the analyzer and the set X-ray intensity threshold. An X-ray analyzer characterized in determining whether or not it is being used. In the X-ray analyzer according to claim 1, the data processing unit compares the X-ray intensity of the energy of a specific element of the sample with the threshold value of the X-ray intensity set, and the sample is X-ray. An X-ray analyzer characterized by determining whether or not it is at the irradiation position. In the X-ray analyzer according to claim 1, the data processing unit compares the X-ray intensity of the energy of a specific element of the surface material of the sample transfer unit with the threshold value of the set X-ray intensity. An X-ray analyzer characterized in determining whether or not a sample is in an X-ray irradiation unit. In the X-ray analyzer according to claim 1, the data processing unit compares the X-ray intensity of the scattered rays of the primary X-ray with the threshold value of the X-ray intensity set, and whether or not the sample is in the X-ray irradiation unit. An X-ray analyzer characterized by determining whether or not. In the X-ray analyzer according to claim 1, the analyzer makes the X-ray intensity of the secondary X-ray detected by the X-ray detector more than the time required for the sample to pass through the X-ray irradiation position. An X-ray analyzer characterized by continuously acquiring spectra at short time intervals. The X-ray analyzer according to claim 1 is characterized in that the data processing unit can select a spectrum at a time when a sample is in the X-ray irradiation unit from a feature amount of a spectrum obtained by machine learning. X-ray analyzer. In the fluorescent X-ray analyzer according to any one of claims 1 to 6, the X-ray spectrum is based on a histogram of X-ray counts in which a range of continuous energy or wavelength is divided at equal intervals. .. The X-ray analyzer according to claim 1 to 5, wherein the X-ray spectrum is a count of a specific energy range or a combination thereof.

Images