X-ray analysis device

Abstract

To demolish a position adjustment mechanism or position adjustment processing for putting a specimen in place in a primary X-ray X1 irradiation area in a fluorescence X-ray analysis device, and to achieve a method of consecutively measuring a plurality of tiny specimens with a simple structure.SOLUTION: A fluorescence X-ray analysis device is configured to include: an X-ray irradiation unit that can irradiate a specimen with an X-ray; an X-ray detection unit that detects a secondary X-ray generating from the specimen; a specimen conveyance part that conveys the specimen; and a data processing unit that processes intensity of the detected X-ray. Respective components are configured to function as follows. The specimen conveyance part is configured to move the specimen so as to pass through the X-ray irradiation position. The X-ray detection unit is configured to acquire an X-ray spectrum at time intervals shorter than time required for the specimen to pass through the X-ray irradiation unit. The data processing unit is configured to select a spectrum at a point of time when the specimen is present in the X-ray irradiation unit on the basis of a characteristic of the X-ray spectrum from an array of the consecutively acquired X-ray spectra.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an X-ray fluorescence analyzer for measuring the composition of a sample and the thickness of a coating. [Background technology]

[0002] X-ray fluorescence analysis is a technique in which a sample is irradiated with X-rays to excite the elements contained in the sample, and the resulting emission of characteristic X-rays specific to each element is analyzed. The resulting X-ray fluorescence spectrum contains information related to the amount of elements present in the area irradiated with X-rays, so by analyzing the spectrum with an appropriate model, the composition ratio of the sample and the film thickness of a multi-layer structure can be determined. Since these analytical processes can often be performed non-destructively and without contact, they are sometimes used for quality control of industrial products, such as plating film thickness testing defined in JIS H8501.

[0003] Due to the principles of X-ray fluorescence analysis, the area irradiated with X-rays becomes the area to be analyzed, so it is necessary to appropriately limit the diameter of the X-rays to match the size of the area to be measured, and to obtain the X-ray fluorescence spectrum with the area to be measured correctly positioned in the X-ray irradiation area.

[0004] In an X-ray fluorescence analysis device that obtains a fluorescent X-ray spectrum with X-rays correctly irradiated onto the target area, the sample to be measured is placed on a sample stage that can be driven on two or three orthogonal axes, and the position of the sample is adjusted so that the measurement site of the sample is located at the X-ray irradiation position, after which the sample is measured in a stationary state. At this time, it is also common to provide an optical system that focuses the X-ray irradiation position with the center of the field of view and observes the sample by optical means, and use this to adjust the sample to the X-ray irradiation position (see Patent Document 1).

[0005] In the case of an X-ray fluorescence analyzer that measures the thickness of a coating on the surface of a long sheet-like sample, the measurement may be performed while the sample is continuously fed past the X-ray irradiation position, and the analysis may be performed as average information of the area on the line that passes through the X-ray irradiation position during the measurement time. Compared to the above-mentioned method of adjusting the sample position and measuring in a stationary state, this eliminates the need for time to adjust the sample position, making it possible to inspect many areas efficiently.

[0006] However, this method is applicable only when the measurement target is continuously distributed on a long sample, and is not applicable when a large number of small sample pieces are fed intermittently. Therefore, we have improved the efficiency of measurements by automating position adjustment and automatically detecting the multiple samples placed on the sample stage.

[0007] There are several approaches to automatic adjustment of the sample position, one of which is based on optical sample observation images. As mentioned above, an optical sample observation means is provided, and the deviation between the irradiation position and the sample is detected using image processing techniques such as pattern matching from the sample image obtained there, and the sample stage is controlled according to the deviation to place the sample at the X-ray irradiation position.

[0008] This first approach is based on the premise that the image of the optical sample observation means and the X-ray irradiation position are aligned or that the relative positions of their axes are accurately known. However, this relative positional relationship may shift due to various factors such as changes over time and thermal expansion. As the measurement target becomes smaller, the effect of the shift between the observation optical axis and the X-ray irradiation axis cannot be ignored.

[0009] In such a case, a second approach is disclosed in Patent Document 2, which is a method of correcting the sample position using the relationship between the stage coordinates and the X-ray intensity. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 06-273147 [Patent Document 2] Japanese Patent Application Publication No. 06-273146 Summary of the Invention [Problem to be solved by the invention]

[0011] In the above conventional technique, the sample position is adjusted and the sample is measured in a stationary state, but the time required for adjusting the sample position poses a problem when inspecting a large number of samples in a short period of time. In addition, a high-definition sample observation optical system and a high-precision multi-axis sample stage are required, which makes the measurement system expensive.

[0012] The present invention has been made in view of the above-mentioned problems, and has an object to provide an X-ray analysis apparatus capable of continuously measuring a large number of small sample pieces without having to keep them stationary. [Means for solving the problem]

[0013] In order to solve the above problems, an X-ray analysis apparatus according to a first aspect of the present invention includes an X-ray source capable of irradiating a sample with X-rays, an X-ray detection unit that detects secondary X-rays generated from the sample, a sample transport unit that transports the sample, an analyzer that discriminates signals output from the X-ray detection unit by energy and counts the number of incidences for each energy to obtain a spectrum as X-ray intensity, and a data processing unit that determines whether the sample being moved by the sample transport unit has passed through the X-ray irradiation position based on a secondary X-ray intensity of an energy of a specific element in the spectrum obtained by the analyzer and a set threshold value of X-ray intensity, wherein the X-ray intensity of an energy of a specific element in a material of a surface of the sample transport unit when the sample is not at the X-ray irradiation position is measured in advance as a first X-ray intensity, and the X-ray intensity when the sample is at the X-ray irradiation position is set as a second X-ray intensity, and the data processing unit sets an X-ray intensity between the first X-ray intensity and the second X-ray intensity as the threshold value.

[0014] An X-ray analysis apparatus according to a second aspect of the present invention comprises an X-ray source capable of irradiating a sample with X-rays, an X-ray detection unit which detects secondary X-rays generated from the sample, a sample transport unit which transports the sample, an analyzer which discriminates signals output from the X-ray detection unit by energy and counts the number of incidences for each energy to obtain a spectrum as X-ray intensity, and a data processing unit which judges whether the sample being moved by the sample transport unit has passed through the X-ray irradiation position based on the secondary X-ray intensity of the energy of a specific element in the spectrum obtained by the analyzer and a set threshold value of X-ray intensity, wherein the X-ray intensity of the energy of a specific element in the material of the surface of the sample transport unit when the sample is not at the X-ray irradiation position is measured in advance and set as a first X-ray intensity, and the data processing unit sets a value lower than the first X-ray intensity as the threshold value.

[0015] The X-ray analysis apparatus according to the third aspect of the present invention is the X-ray intensity group is a set of X-ray intensities of a specific element in a surface material of the sample transport unit when the sample is not at the X-ray irradiation position, and a first X-ray intensity group is a set of X-ray intensity groups obtained in advance; and the second X-ray intensity group is a set of X-ray intensity groups obtained in advance; the X-ray intensity group is a set of X-ray intensity groups obtained in advance; and the second X-ray intensity group is a set of X-ray intensity groups obtained in advance;

[0016]

[0017]

[0018] In the present invention, an X-ray spectrum based on a histogram of X-ray counts in a continuous energy or wavelength range divided at equal intervals can also be used.

[0019] In the present invention, an X-ray spectrum obtained by counting a specific energy range or a combination of multiple energy ranges can also be used. Effect of the Invention

[0020] According to the present invention, an X-ray fluorescence analyzer can be calibrated using an X-ray irradiation unit capable of irradiating a sample with X-rays, an X-ray detection unit that detects secondary X-rays generated from the sample, a sample transport unit that transports the sample, and a data processing unit that processes the detected X-ray intensity, and a position adjustment mechanism and position adjustment process for placing the sample in the primary X-ray irradiation area can be eliminated, resulting in a simple configuration. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic overall configuration diagram showing an X-ray apparatus in a state where a sample is not irradiated with primary X-rays, in an embodiment of an X-ray fluorescence apparatus according to the present invention. [Diagram 2] FIG. 1 shows a spectrum when the sample is not irradiated with primary X-rays. [Diagram 3] 1 is a schematic overall configuration diagram showing an X-ray apparatus in a state in which a sample is irradiated with primary X-rays in an embodiment of an X-ray fluorescence apparatus according to the present invention. [Figure 4] FIG. 1 is a diagram showing a spectrum when a sample is irradiated with primary X-rays. [Diagram 5] FIG. 13 shows spectra measured continuously at predetermined time intervals while transporting a sample. [Figure 6] FIG. 13 is a diagram showing a spectrum when the sample transport part is made of plastic. [Figure 7] This is a spectrum diagram showing energy in channels separated by equal intervals ΔE. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of an X-ray analysis apparatus according to the present invention will be described with reference to the drawings.

[0023] The X-ray analysis apparatus of this embodiment includes a sample transport unit 3 on which a sample S is placed and which can be moved in a transport direction D, an X-ray irradiation unit 1 which irradiates primary X-rays X1 onto the sample S, a primary X-ray adjustment means 4 which shapes the irradiation diameter of the primary X-rays X1 irradiated onto the sample, an X-ray detection unit 2 which detects secondary X-rays such as scattered X-rays and fluorescent X-rays generated from the sample S irradiated with the primary X-rays X1, an analyzer 5 connected to the X-ray detector 2 which analyzes a signal of energy information of the secondary X-rays, and a data processing unit 7 connected to the analyzer 5. FIG. 1 shows a case where the sample S is not at the irradiation position 6. FIG. 3 also shows the case where the sample S is at the irradiation position 6.

[0024] The X-ray irradiation unit 1, which irradiates the sample S with primary X-rays X1, uses an X-ray tube. The X-ray tube is housed in a housing that is equipped with appropriate insulation for the high voltage applied, a cooling mechanism for discharging the generated heat, and shielding of X-rays in unnecessary directions for safety. The primary X-ray adjustment means 4 can use, for example, a collimator with fine holes made of a material such as tungsten or brass with a sufficiently large X-ray shielding capacity, or an X-ray focusing element such as a polycapillary or monocapillary that utilizes the total reflection phenomenon inside a hollow glass tube. The irradiation diameter formed by the primary X-ray adjustment means 4 is determined based on the size of the sample S and the transport speed of the sample transport unit 3, which can move the sample S in the transport direction D while placing it thereon. If the position of the sample S in the direction perpendicular to the transport direction D cannot be ignored compared to the size of the sample, the amount of deviation is also taken into consideration when determining the irradiation diameter. As an example, the irradiation diameter is set to a value that is approximately the size of the sample minus the expected amount of positional deviation. As a result, when the sample is at the irradiation position, all the fluorescent X-rays generated can be practically considered to be from the sample.

[0025] The sample transport unit 3 is a belt conveyor with an endless belt wound around a pair of rollers, on which the sample S is placed and which can be moved relative to one another in a predetermined scanning direction to continuously transport the sample S. The surface material of the sample transport unit 3 on which the sample S is placed is selected from one which does not interfere with the energy of the secondary X-rays generated from the surface of the sample transport unit 3 with the energy of the secondary X-rays generated from the sample S. For example, when the sample S is made of copper (Cu) or nickel (Ni), the surface material of the sample transport unit 3 is aluminum (Al). The sample transport unit 3 is positioned so that the trajectory of the movement of the mounted sample S passes through the irradiation position 6 where the primary X-rays X1 are irradiated.

[0026] Here, the arrangement of the samples in the direction perpendicular to the sample transport direction D is restricted in consideration of the irradiation diameter of the primary X-rays X1, but the arrangement in the sample transport direction D, i.e., the interval at which each sample S is transported, is limited to a minimum that at least one measurement point where no sample is present is sandwiched between two consecutive samples, and there is no restriction as long as it is greater than this interval, and it does not need to be equal intervals. The shape of the sample transport section 3 is not limited to a belt conveyor, disk shape, etc., and the trajectory along which the sample is transported intersects with the primary X-rays X1. The number of samples to be transported may be one.

[0027] The X-ray detection unit 2 uses an energy dispersive 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 this electric charge into a voltage signal proportional to the amount of electric charge, and then converts this to an AD signal and outputs it as a digital value. The X-ray detection section may use a wavelength dispersive X-ray detector.

[0028] The analyzer 5 is connected to the X-ray detection unit 2 and analyzes the signal. The analyzer 5 is, for example, a pulse height analyzer (multi-channel analyzer) that obtains the pulse height of the voltage pulse from the signal and generates an energy spectrum. The analyzer 5 discriminates the X-ray photon signal output from the X-ray detection unit 2 by energy, counts the number of incidences for each energy, and obtains a spectrum as X-ray intensity.

[0029] 7 shows that the analyzer 5 discriminates the energy by energy, counts the number of incidences for each energy, and expresses the X-ray intensity as an array of counts for each channel 42, with multiple channels 42 divided into equal intervals ΔE. The time Tm for accumulating the incidence counts is set to satisfy the following formula 1.

number

[0030] 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 preferable that the time Tm for integrating the incident counts is shorter than the time required for the sample to pass through the X-ray irradiation unit.

[0031] This spectrum accumulation operation is performed continuously, and the obtained spectrum is stored as a spectrum array in the memory of the data processing unit 7. The data processing unit 7 judges whether the sample S being moved by the sample transport unit 3 has passed the irradiation position 6 or not, based on the obtained spectrum and a set threshold value. In addition, the spectra stored in the memory of the data processing unit 7 are overwritten with the oldest spectra to prevent the memory area from becoming saturated. However, by implementing the memory so that a sufficiently large number of spectra can be written at one time, the spectra are not overwritten by the next spectrum within the time required for subsequent processing.

[0032] The analyzer 5 is a pulse height analyzer (multi-channel pulse height analyzer) that obtains the pulse 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 that are successively acquired, and detects changes in the spectra due to the presence or absence of the sample S.

[0033] The following describes a case where the main component of the material of the sample transport part 3 is element A, and the main component of the sample S is element B. Figure 2 shows spectrum 10 with energy on the horizontal axis and X-ray intensity on the vertical axis when sample S is not at irradiation position 6 as in Figure 1. Since the surface of sample transport part 3 is at irradiation position 6, spectrum 10 has an X-ray intensity peak at energy 11 of the fluorescent X-ray of element A, the main component of the material of sample transport part 3. Next, Figure 4 shows spectrum 12 when sample S is at irradiation position 6 as in Figure 3. Since sample S is at irradiation position 6, it has an X-ray intensity peak at energy 13 of the fluorescent X-ray of element B, the main component of sample S. In this case, the X-ray intensity at energy 11 of the fluorescent X-ray of element A in Figure 4 is smaller than that in Figure 2. By utilizing this property, a predetermined X-ray intensity threshold 14 is set, and when the X-ray intensity of the fluorescent X-ray energy 13 of element B, which is the main component of sample S, exceeds threshold 14, it is determined that sample S is present at irradiation position 6.

[0034] In this embodiment, Tm is set to 1 / 10 of L / V as described above, so that spectra T1 to T21 are shown, which are measured continuously at predetermined time intervals while the sample S is being transported, as shown in FIG. In the case of FIG. 5, in spectra T2 to T20, the X-ray intensity of the fluorescent X-ray energy 13 of element B is greater than the threshold value 14, so it is determined that the sample S is at the irradiation position 6. The X-ray intensity of the determined energy 13 is analyzed as the measured spectrum of the sample. These consecutive measured spectra are all treated as individual spectra. Alternatively, the first and last measured spectra, such as spectra T2 and T20, may be excluded, and T3 to T29 may be integrated or averaged and treated as a single spectrum. Alternatively, the center or centroid of the consecutive measured spectra may be selected as the spectrum of the sample.

[0035] In the X-ray analysis apparatus of the present embodiment described above, whether or not the sample S is present at the irradiation position 6 is determined based on the X-ray intensity of the fluorescent X-ray energy 13 of element B, which is the main component of the sample S. However, the presence or absence of a sample may also be determined by using the X-ray intensity of the fluorescent X-ray energy of element A, which is the main component of the material of the sample transport section, and a specific threshold value. The threshold value at this time may be different from the threshold value in the above-described embodiment. 2 and 4, the X-ray intensity of the energy 11 of the fluorescent X-rays of 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 at the irradiation position 6, the amount of primary X-rays X1 irradiated onto the sample transport unit 3 is attenuated, and the X-ray intensity of the energy 11 of the fluorescent X-rays of element A is significantly attenuated. By setting a specific threshold value for element A, it may be possible to determine whether the sample S is at the irradiation position 6 by comparing the X-ray intensity of the energy 11 of the fluorescent X-rays of element A with this threshold value.

[0036] In addition, in the X-ray analysis apparatus of the present embodiment, when the surface of the sample transport unit 3 is made of a plastic material, the plastic has a high efficiency of scattering primary X-rays, and in addition, the fluorescent X-ray peaks of carbon and oxygen, which are the main components of plastics, are hardly detected. Therefore, when the sample S is not at the irradiation position 6, as shown in spectrum 15 in FIG. 6, the spectrum of scattered rays reflecting the continuous X-ray component from the X-ray tube is significantly broader than the fluorescent X-ray peaks. By utilizing this property, it may be possible to determine whether or not the spectrum is that of the sample S at the irradiation position 6 when the X-ray intensity in the energy region 16 where the intensity of the scattered rays is significant and does not interfere with the energy 13 of element B, which is the main component of the sample S, falls below a threshold value 17.

[0037] Another embodiment of the X-ray analysis apparatus will be described for cases where the material of the sample transport unit 3 cannot be selected so as not to cause interference between the material of the sample S and the fluorescent X-rays, or where the components of the sample S are unstable and it is difficult to set an appropriate threshold value. As a preparation step, a large number of spectra are obtained without the sample S placed on it, and then a spectrum is obtained with the sample placed at or near the irradiation position. If differences in the spectra between samples are expected due to individual sample differences other than measurement system variations, such as variations in sample components or coating thickness, care should be taken to include spectra from a large number of samples that appropriately reflect the variations in the individual differences between samples. The differences between the spectra of these two groups are learned by deep learning. Using the learning results obtained in the preparation stages up to this point, it is determined whether the spectrum is that of sample S when it is at irradiation position 6.

[0038] As shown in FIG. 7, the spectrum generated by the X-ray detection unit 2 is an array of counts for each energy range divided at equal intervals. In this case, the X-ray intensity of the fluorescent X-ray energy 11 of the element A, the main component of the material of the sample transport unit, is A0 From E A1 Similarly, the X-ray intensity of the energy 13 of the X-ray of the main component of the sample S, element B, is given by the sum of the counts of the channels between energy E B0 From E B1 This method is reasonable when the peak shape of the spectrum is important in the later data processing, but the fluorescence X-ray intensity of each element is calculated as the sum of the counts of the channels between E A0 From E A1 Between and E B0 From E B1 In cases where it is sufficient to obtain the sum of the counts between the elements, it is not necessary to divide the channels at equal intervals to generate a spectrum. In such cases, the object of the present invention can be achieved by not dividing the channels at equal intervals, but by setting energy regions including the energy peaks of the required elements as several channels and operating them as multiple single-channel analyzers. [Explanation of symbols]

[0039] 1 X-ray irradiation section 2 X detector 3. Sample transport section 4 Primary X-ray adjustment means 5 Analyzer 6 Irradiation position 7 Data Processing Section X1 Primary X-ray X2 Secondary X-ray D Sample transport direction

Claims

1. An X-ray source capable of irradiating a sample with X-rays; an X-ray detection unit for detecting secondary X-rays generated from the sample; A sample transport unit that transports the sample; an analyzer for discriminating signals output from the X-ray detection unit by energy and counting the number of incidences for each energy to obtain a spectrum as X-ray intensity; and a data processing unit that determines whether or not the sample being moved by the sample transport unit has passed the X-ray irradiation position based on a secondary X-ray intensity of a specific element energy in the spectrum obtained by the analyzer and a set threshold value of the X-ray intensity, an X-ray intensity of an energy of a specific element in a material of a surface of the sample transport unit when the sample is not at an irradiation position of the X-rays is measured in advance and set as a first X-ray intensity; When the X-ray intensity when the sample is at the X-ray irradiation position is defined as a second X-ray intensity, The X-ray analysis apparatus according to claim 1, wherein the data processing unit sets an X-ray intensity between the first X-ray intensity and the second X-ray intensity as the threshold value.

2. An X-ray source capable of irradiating a sample with X-rays; an X-ray detection unit for detecting secondary X-rays generated from the sample; A sample transport unit that transports the sample; an analyzer for discriminating signals output from the X-ray detection unit by energy and counting the number of incidences for each energy to obtain a spectrum as X-ray intensity; and a data processing unit that determines whether or not the sample being moved by the sample transport unit has passed the X-ray irradiation position based on a secondary X-ray intensity of a specific element energy in the spectrum obtained by the analyzer and a set threshold value of the X-ray intensity, an X-ray intensity of an energy of a specific element in a material of a surface of the sample transport unit when the sample is not at an irradiation position of the X-rays is measured in advance and set as a first X-ray intensity; The X-ray analysis apparatus according to claim 1, wherein the data processing unit sets the threshold value to a value lower than the first X-ray intensity.

3. An X-ray source capable of irradiating a sample with X-rays; an X-ray detection unit for detecting secondary X-rays generated from the sample; A sample transport unit that transports the sample; an analyzer for discriminating signals output from the X-ray detection unit by energy and counting the number of incidences for each energy to obtain a spectrum as X-ray intensity; and a data processing unit that determines whether or not the sample being moved by the sample transport unit has passed the X-ray irradiation position based on a secondary X-ray intensity of a specific element energy in the spectrum obtained by the analyzer and a set threshold value of the X-ray intensity, a first X-ray intensity group is a group of X-ray intensities of energy of a specific element in a material of a surface of the sample transport unit that is previously measured when the sample is not at an irradiation position of the X-rays; A second X-ray intensity group is a group of X-ray intensities obtained when the sample is at or near the irradiation position of the X-rays. The data processing unit learns the differences in the spectra of the first X-ray intensity group and the second X-ray intensity group through machine learning, and determines whether the sample has passed through the X-ray irradiation position based on the features of the spectra obtained through the machine learning.

4. 2. The X-ray analysis apparatus according to claim 1, wherein the analyzer continuously acquires a spectrum of the X-ray intensity of the secondary X-rays detected by the X-ray detection unit at a time interval shorter than the time required for the sample to pass through the X-ray irradiation position.

5. 5. The X-ray fluorescence analysis apparatus according to claim 1, wherein the X-ray spectrum is a histogram of X-ray counts in a range of continuous energy or wavelength divided at equal intervals.

6. 6. The X-ray fluorescence analysis apparatus according to claim 1, wherein the X-ray spectrum is a count in a specific energy range or a combination of a plurality of counts in the specific energy range.

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