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 by the X-rays, so by analyzing the spectrum with an appropriate model, it is possible to determine the composition ratio of the sample and the film thickness of a multilayer structure. 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 as 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. Therefore, it is necessary to appropriately limit the diameter of the irradiated X-rays to match the size of the measurement area, and to acquire the X-ray fluorescence spectrum with the measurement area correctly positioned in the X-ray irradiation area.

[0004] In an X-ray fluorescence analyzer that acquires an X-ray fluorescence spectrum with X-rays correctly irradiated onto the target region, the sample to be measured is placed on a sample stage that can be driven on two or three orthogonal axes, and the sample position is adjusted so that the measurement portion of the sample is positioned at the X-ray irradiation position, after which measurement is performed while the sample is stationary. In this case, it is 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 measuring the thickness of a coating on the surface of a long sheet-like sample, the measurement is sometimes performed while the sample is continuously fed past the X-ray irradiation position, and the analysis is performed as average information for the area on the line that passes through the X-ray irradiation position during the measurement period. Compared to the method of adjusting the sample position and measuring in a stationary state, this method eliminates the need for sample position adjustment and makes it possible to inspect many areas efficiently.

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

[0007] There are several approaches to automatically adjusting the sample position, one of which is to use optical sample observation images. As mentioned above, an optical sample observation device is provided, and the sample image obtained therefrom is used to detect any deviation between the irradiation position and the sample using image processing techniques such as pattern matching. The sample stage is then controlled according to the deviation, and the sample is positioned at the X-ray irradiation position.

[0008] This first approach assumes that the image from the optical sample observation tool and the X-ray irradiation position are aligned, or that the relative positions of their axes are accurately known. However, this relative positional relationship can shift due to various factors, such as changes over time and thermal expansion. The smaller the measurement target, the more difficult it is to ignore the effect of this misalignment between the observation optical axis and the X-ray irradiation axis.

[0009] In such a case, Patent Document 2 discloses a second approach in which the sample position is corrected 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 conventional method described above, the sample position is adjusted and then measured while the sample is stationary, which poses a challenge for inspecting a large number of samples in a short period of time due to the time required for sample position adjustment. Furthermore, a high-resolution 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 as its object to provide an X-ray analysis apparatus that is 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, the present invention of The X-ray analysis device 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, and a detector that detects the sample. The sample is placed on a surface and passes through an irradiation position where the X-rays are irradiated. a sample transport unit for transporting the sample; With or without the sample, an analyzer that discriminates the signal output from the X-ray detection unit by energy and counts the number of incidents for each energy to obtain a spectrum as X-ray intensity; Process the detected X-ray intensity a data processing unit; The analyzer continuously acquires a plurality of the spectra at time intervals shorter than the time required for the sample to pass through the irradiation position, and the data processing unit stores the spectra in a memory as a spectrum array, and determines that the sample is at the irradiation position at a time corresponding to a spectrum at a time point when the sample is at the irradiation position based on the intensity of an element that characterizes whether the sample is at the irradiation position, from the spectrum array, and further uses the spectrum at the time point when the sample is at the irradiation position as a measured spectrum of the sample. This is an X-ray analysis device characterized by the above.

[0014] In the X-ray analysis apparatus according to claim 1, the X-ray intensity of the energy of a specific element contained in the sample can be used as the element intensity characterizing whether the sample is present at the irradiation position or not. In the X-ray analysis apparatus according to claim 1, the X-ray intensity of the energy of a specific element in the material of the surface of the sample transport part can be used as the element intensity characterizing whether the sample is present at the irradiation position or not.

[0015] In the X-ray analysis apparatus according to claim 1, the X-ray intensity of the scattered rays of the primary X-rays can be used as the element intensity that characterizes whether the sample is present at the irradiation position or not.

[0016]

[0017]

[0018] In the present invention, an X-ray spectrum based on a histogram of X-ray counts in a range of continuous energy or wavelength divided into 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. [Effects 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. This eliminates the need for a position adjustment mechanism or process for positioning the sample in the primary X-ray irradiation area, and allows for a simple configuration. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic overall configuration diagram showing an X-ray apparatus in an embodiment of the fluorescent X-ray apparatus according to the present invention in a state where a sample is not irradiated with primary X-rays. [Figure 2] FIG. 10 is a diagram showing a spectrum when the sample is not irradiated with primary X-rays. [Figure 3] 1 is a schematic overall configuration diagram showing an X-ray apparatus in a state where a sample is irradiated with primary X-rays in an embodiment of the 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. [Figure 5] FIG. 10 shows spectra measured continuously at predetermined time intervals while transporting a sample. [Figure 6] FIG. 10 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 INVENTION

[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 that can carry a sample S and move in a transport direction D, an X-ray irradiation unit 1 that irradiates primary X-rays X1 onto the sample S, a primary X-ray adjustment means 4 that shapes the irradiation diameter of the primary X-rays X1 irradiated onto the sample, an X-ray detection unit 2 that 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 that analyzes signals containing energy information about 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 equipped with appropriate insulation for the applied high voltage, a cooling mechanism to remove generated heat, and shielding from unwanted X-rays for safety. The primary X-ray adjustment unit 4 can be, for example, a collimator with fine holes made of a material such as tungsten or brass with sufficient X-ray shielding capacity, or an X-ray focusing element such as a polycapillary or monocapillary that utilizes total reflection inside a hollow glass tube. The irradiation diameter formed by the primary X-ray adjustment unit 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. If the position of the sample S in the direction perpendicular to the transport direction D is significant compared to the sample size, the amount of misalignment must also be taken into account when determining the irradiation diameter. For example, the irradiation diameter is set to a value approximately equal to the sample size minus the expected amount of misalignment. This allows all fluorescent X-rays generated when the sample is in the irradiation position to be considered to be coming from the sample.

[0025] The sample transport unit 3 is a belt conveyor with an endless belt wound around a pair of rollers, and can continuously transport the sample S by placing it on it and moving it relatively in a predetermined scanning direction. The surface material of the sample transport unit 3 on which the sample S is placed is selected to be one that does not interfere with the energy of the secondary X-rays generated from the surface of the sample transport unit 3. For example, if 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 loaded 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 by taking into account the irradiation diameter of the primary X-rays X1, but the arrangement in the sample transport direction D, i.e., the interval at which individual samples S are transported, is limited to a minimum so that there is at least one measurement point where no sample is present between two consecutive samples, and there is no restriction as long as it is greater than this interval, and the intervals do not need to be equal. The shape of the sample transport unit 3 is not limited to a belt conveyor or a disk, etc., as long as 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 into an AD signal to output it as a digital value. The X-ray detection unit 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 signals output from the X-ray detection unit 2 by energy, counts the number of incidents for each energy, and obtains a spectrum as X-ray intensity.

[0029] 7 shows the X-ray intensity obtained by discriminating the energy by the analyzer 5, counting the number of incidents for each energy, and arranging a plurality of channels 42 in which the energy of the spectrum is divided into equal intervals ΔE, and expressing the count array for each channel 42. The time Tm for accumulating these incident counts is set to satisfy the following mathematical 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 desirable 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 carried out 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 determines whether the sample S being moved by the sample transport unit 3 has passed the irradiation position 6 based on the obtained spectrum and a set threshold value. Furthermore, the spectra stored in the memory of the data processing unit 7 are overwritten in chronological order 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] We will explain the case where the main component of the material of the sample transfer unit 3 is element A, and sample S contains element B as a main component. 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. Because the surface of sample transfer unit 3 is at irradiation position 6, spectrum 10 has an X-ray intensity peak at energy 11 of the fluorescent X-rays of element A, the main component of the material of sample transfer unit 3. Next, Figure 4 shows spectrum 12 when sample S is at irradiation position 6 as in Figure 3. Because sample S is at irradiation position 6, it has an X-ray intensity peak at energy 13 of the fluorescent X-rays of element B, the main component of sample S. In this case, the X-ray intensity at energy 11 of the fluorescent X-rays of element A in Figure 4 is smaller than in Figure 2. By utilizing this property, a predetermined threshold value 14 of X-ray intensity 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 value 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, and therefore, as shown in FIG. 5, spectra T1 to T21 are shown which were measured continuously at predetermined time intervals while the sample S was being transported. In the case of Figure 5, in spectra T2 to T20, the X-ray intensity of the fluorescent X-rays of element B at energy 13 is greater than threshold 14, so it is determined that sample S is at irradiation position 6. The X-ray intensity at 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, can be excluded, and T3 to T29 can be integrated or averaged and treated as a single spectrum. Alternatively, the center or centroid of the consecutive measured spectra can be selected as the spectrum of the sample.

[0035] In the X-ray analysis apparatus of the present embodiment, 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 and a specific threshold value for the fluorescent X-ray energy of element A, which is the main component of the material of the sample transport section. The threshold value at this time may be different from the threshold value in the present 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 is 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 another embodiment of the X-ray analysis apparatus, when the surface of the sample transport unit 3 is made of a plastic material, plastics have a high scattering efficiency of primary X-rays, and 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, 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, as shown in spectrum 15 in FIG. 6. Taking advantage of this property, it may be possible to determine whether the spectrum is for when the sample S is at the irradiation position 6 by checking whether the X-ray intensity in energy region 16 where the intensity of scattered rays is significant and does not interfere with energy 13 of element B, the main component of the sample S, falls below threshold 17.

[0037] Another example of the X-ray analysis apparatus of this embodiment is described below for cases where the material of the sample transport unit 3 cannot be selected so as not to interfere with 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 acquired without the sample S placed on it, and then a spectrum is acquired with the sample placed at or near the irradiation position. If differences in the spectra between samples are predicted due to individual differences other than measurement system variations, such as variations in sample composition 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 using 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 Figure 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 of the element A, whose main component is the material of the sample transport unit, is energy 11. A0 From E A1 Similarly, the X-ray intensity of the energy 13 of the X-rays of the main component of the sample S, element B, is given as the sum of the counts of the channels between B0 From E B1 This method is reasonable when the peak shape of the spectrum is important in the subsequent data processing. However, in the subsequent data processing, the fluorescent 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 If it is sufficient to simply sum the counts between the two, 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 several channels in energy ranges that include the energy peaks of the required elements, and operating the analyzers 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 that detects secondary X-rays generated from the sample; a sample transport unit that places the sample on a surface and transports the sample so that the sample passes through an irradiation position where the X-rays are irradiated; an analyzer that discriminates the signal output from the X-ray detection unit for each energy, regardless of whether a sample is present or not, and counts the number of incidents for each energy to obtain a spectrum as X-ray intensity; and a data processing unit that processes the detected X-ray intensity, The analyzer successively acquires a plurality of the spectra at time intervals shorter than the time required for the sample to pass through the irradiation position; the data processing unit stores the spectrum in a memory as a spectrum array; and determining, based on the intensity of an element that characterizes whether the sample is at the irradiation position or not, the time corresponding to the spectrum at the time when the sample is at the irradiation position from the spectrum array, as the time when the sample is at the irradiation position; Furthermore, the X-ray analysis apparatus is characterized in that the spectrum at the time when the sample is at the irradiation position is used as the measured spectrum of the sample.

2. An X-ray analysis apparatus as described in claim 1, characterized in that the X-ray intensity of the energy of a specific element contained in the sample is used as the elemental intensity that characterizes whether the sample is present at the irradiation position or not.

3. An X-ray analysis apparatus as described in claim 1, characterized in that the X-ray intensity of the energy of a specific element in the material of the surface of the sample transport section is used as the elemental intensity that characterizes whether the sample is at the irradiation position or not.

4. 2. The X-ray analysis apparatus according to claim 1, wherein the X-ray intensity of scattered rays of primary X-rays is used as the element intensity characterizing whether the sample is present at the irradiation position or not.

5. 5. The X-ray fluorescence analyzer 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. 5. The X-ray fluorescence analyzer 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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