X-ray analysis equipment

Abstract

An X-ray analysis device is provided. A method for continuously measuring a large number of small samples using a simple structure is achieved without requiring a position adjustment mechanism and a position adjustment process for arranging the sample in a primary X-ray (X1) irradiation area. The fluorescence X-ray analysis device is constructed to include an X-ray irradiation unit capable of irradiating the sample with X-rays, an X-ray detection unit for detecting secondary X-rays generated from the sample, a sample transport unit for transporting the sample, and a data processing unit for processing the detected X-ray intensity, so that each structural element has the following functions. The sample transport unit moves the sample so that the sample passes through the X-ray irradiation position. The X-ray detection unit continuously obtains X-ray energy spectra at time intervals shorter than the time required for the sample to pass through the X-ray irradiation unit. The data processing unit selects an energy spectrum at the moment when the sample is located in the X-ray irradiation unit according to the arrangement of the continuously obtained X-ray energy spectra and the characteristics of the X-ray energy spectra.

Description

Technical Field

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

[0002] Fluorescence X-ray analysis involves irradiating a sample with X-rays to excite the elements contained within it, and then analyzing the characteristic X-rays emitted as a result of the excitation. The resulting fluorescence X-ray energy spectrum contains information related to the amount of elements present in the area irradiated by the X-rays. Therefore, by analyzing the energy spectrum using appropriate models, it is possible to determine the sample's composition ratio, the thickness of multilayer structures, and other information. In many cases, these analyses can be performed non-destructively and contact-free, making them sometimes used in industrial product quality management, such as for plating thickness testing as defined in JIS H8501.

[0003] According to the principle of fluorescence X-ray analysis, the area irradiated by X-rays becomes the target area for analysis. Therefore, the irradiation diameter of the X-rays must be appropriately limited according to the size of the measurement area, and the fluorescence X-ray energy spectrum must be acquired with the target area precisely positioned within the X-ray irradiation area.

[0004] In a fluorescence X-ray analysis device that obtains a fluorescence X-ray energy spectrum while accurately irradiating the target area with X-rays, the sample to be measured is placed on a sample stage capable of being driven along two or three orthogonal axes. After adjusting the position of the sample so that the measurement portion is located at the X-ray irradiation position, the measurement is performed while the sample is stationary. In this case, an optical system is generally provided that focuses the X-ray irradiation position at the center of the field of view and observes the sample using an optical unit. This optical system is then used to adjust the sample to the X-ray irradiation position. (See Patent Document 1)

[0005] Furthermore, when using a fluorescent X-ray analyzer to measure the thickness of a coating applied to the surface of a long sheet sample, a method is sometimes employed in which the sample is continuously transported through the X-ray irradiation position while the measurement is performed. During the measurement period, average information is analyzed for the area along the line passing through the X-ray irradiation position. Compared to the aforementioned method of adjusting the sample position and performing the measurement while the sample is stationary, this method eliminates the need for time-consuming sample position adjustment and allows for efficient inspection of multiple locations.

[0006] However, this method can be applied to a case where the measurement target is continuously distributed on a long sample, but cannot be applied to a case where a large number of small samples are transported intermittently.

[0007] Therefore, by automating the position adjustment, a large number of samples placed on the sample stage can be automatically detected, thereby achieving improved measurement efficiency.

[0008] There are several methods for automatically adjusting the sample position, one of which is the use of optical sample observation images. As described above, an optical sample observation unit is installed. Using the resulting sample image, image processing techniques, including pattern matching, are used to detect the offset between the irradiation position and the sample. The sample stage is then controlled based on this offset to position the sample at the X-ray irradiation position.

[0009] This first method assumes that the image of the optical sample observation unit is consistent with the X-ray irradiation position, or that the relative positions of the axes are accurately known. However, these relative positions can sometimes shift due to various factors such as time-dependent changes and thermal expansion. The smaller the object being measured, the more important it is to consider the impact of this shift between the observation optical axis and the X-ray irradiation axis.

[0010] In this case, as a second method, Patent Document 2 discloses a method of correcting the sample position using the relationship between the stage coordinates and the X-ray intensity.

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 06-273147

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 06-273146

[0013] In the above-mentioned prior art, the sample position is adjusted and the measurement process is performed while the sample is stationary. Since sample position adjustment takes time, it is difficult to inspect a large number of samples in a short period of time. In addition, there is the problem of requiring a highly precise sample observation optical system and a high-precision multi-axis sample stage, which makes the measurement system expensive. Summary of the Invention

[0014] 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 analysis apparatus capable of continuously measuring a large number of small sample pieces without the samples being stationary.

[0015] In order to solve the above-mentioned problems, in the present invention, an X-ray analysis device is characterized in that the X-ray analysis device comprises: 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; a sample transport unit that transports the sample; an analyzer that continuously obtains an X-ray energy spectrum of the X-ray intensity of the secondary X-rays detected by the X-ray detection unit at time intervals shorter than the time required for the sample to pass through the X-ray irradiation position; and a data processing unit that determines whether the sample moved by the sample transport unit is passing through the X-ray irradiation position based on the secondary X-ray intensity of the energy of a specific element in the energy spectrum obtained by the analyzer and a set X-ray intensity threshold.

[0016] The X-ray analysis apparatus of the present invention is characterized in that the data processing unit compares the X-ray intensity of the energy of a specific element of the sample with the set X-ray intensity threshold to determine whether the sample is located at the X-ray irradiation position.

[0017] The X-ray analysis device of the present invention is characterized in that the data processing unit compares the X-ray intensity of the energy of a specific element of the material on the surface of the sample transport unit with a set X-ray intensity threshold to determine whether the sample is located at the X-ray irradiation position.

[0018] The X-ray analysis apparatus of the present invention is characterized in that the data processing unit compares the X-ray intensity of scattered rays of the primary X-ray with the set X-ray intensity threshold to determine whether the sample is located at the irradiation position of the X-ray.

[0019] A fifth aspect of the present invention for solving the above-mentioned problems is characterized in that, in the first aspect, the data processing unit selects an energy spectrum at a time when the sample is located at an X-ray irradiation position from feature quantities of the energy spectrum obtained by machine learning.

[0020] A sixth aspect of the present invention for solving the above-mentioned problems is characterized in that, in the first to fifth aspects, an X-ray energy spectrum consisting of a histogram of X-ray counts obtained by dividing a continuous energy or wavelength range at equal intervals is used.

[0021] A seventh aspect of the present invention for solving the above-mentioned problems is characterized in that, in the first to fifth aspects, an X-ray energy spectrum based on counts in a specific energy range or a combination of a plurality of counts is used.

[0022] Effects of the Invention

[0023] According to the present invention, a fluorescence X-ray analysis device can be calibrated by an X-ray irradiation unit that can irradiate 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. The position adjustment mechanism and position adjustment process for arranging the sample in the primary X-ray irradiation area can be omitted, and this can be achieved using a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram schematically showing the overall configuration of the X-ray apparatus in an embodiment of the fluorescent X-ray apparatus of the present invention, in a state where a sample has not been irradiated with primary X-rays.

[0025] Figure 2 This is a diagram showing an energy spectrum in a state where the sample has not been irradiated with X-rays once.

[0026] Figure 3 This is a schematic overall configuration diagram of an X-ray apparatus showing a state in which a sample is irradiated with X-rays once in an embodiment of the fluorescent X-ray apparatus of the present invention.

[0027] Figure 4 This is a diagram showing an energy spectrum when a sample is irradiated with X-rays once.

[0028] Figure 5 This is a diagram showing energy spectra measured continuously at predetermined time intervals while a sample is being transported.

[0029] Figure 6 This is a diagram showing an energy spectrum when the sample transport unit is made of plastic.

[0030] Figure 7 This is an energy spectrum diagram showing energy channels divided at equal intervals of ΔE.

[0031] Description of labels

[0032] 1: X-ray irradiation unit; 2: X-ray detection unit; 3: Sample transport unit; 4: Primary X-ray adjustment unit; 5: Analyzer; 6: Irradiation position; 7: Data processing unit; X1: Primary X-ray; X2: Secondary X-ray; D: Sample transport direction. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the X-ray analysis apparatus according to the present invention will be described with reference to the accompanying drawings.

[0034] The X-ray analysis apparatus of this embodiment comprises: a sample transport unit 3 capable of carrying a sample S and moving in a transport direction D; an X-ray irradiation unit 1 for irradiating the sample S with primary X-rays X1; a primary X-ray adjustment unit 4 for shaping the irradiation diameter of the primary X-rays X1 irradiated to the sample; an X-ray detection unit 2 for detecting secondary X-rays such as scattered X-rays or 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 for analyzing a signal of energy information of the secondary X-rays; and a data processing unit 7 connected to the analyzer 5. Figure 1 , which shows the case where the sample S is not located at the irradiation position 6. Figure 3 , the sample S is located at the irradiation position 6 .

[0035] 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 provides adequate insulation against the high voltage to be applied, shields X-rays from unnecessary directions for safety reasons, and includes a cooling mechanism for dissipating the generated heat. The primary X-ray adjustment unit 4 can be composed of, for example, a collimator with fine holes in a material such as tungsten or brass with sufficient X-ray shielding capability, or an X-ray converging element such as a polycapillary or monocapillary tube that utilizes total reflection from the inner surface of a hollow glass tube. The irradiation diameter formed by the primary X-ray adjustment unit 4 is determined by the size of the sample S and the transport speed of the sample transport unit 3, which is capable of carrying the sample S and moving it in the transport direction D. If the sample S's placement in a direction perpendicular to the transport direction D is not negligible relative to the sample's size, the irradiation diameter is determined by also taking into account the offset. As an example, the irradiation diameter is set to the size of the sample minus the assumed placement offset. This allows for practical application of the irradiation diameter, as the sample is positioned at the irradiation position, to ensure that all generated fluorescent X-rays are considered to originate entirely from the sample.

[0036] The sample transport unit 3 is a belt conveyor formed by winding an endless belt around a pair of rollers, and is capable of carrying the sample S and continuously transporting the sample S in a relatively movable manner in a predetermined scanning direction. The surface material of the sample transport unit 3 on which the sample S is carried 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 material of the surface of the sample transport unit 3. In addition, the sample transport unit 3 is configured so that the movement trajectory of the carried sample S passes through the irradiation position 6 irradiated by the primary X-ray X1.

[0037] Here, the irradiation diameter of the primary X-ray X1 is considered to limit the placement of samples perpendicular to the sample transport direction D. However, regarding the placement of samples in the transport direction D, that is, the spacing between each sample S, the minimum requirement is that measurements be performed with at least one sample between two consecutive samples. There are no restrictions for spacing greater than this, and even spacing is not required. The shape of the sample transport unit 3 is not limited, and can be a disc or other shape, in addition to a belt conveyor. The trajectory of the sample transport intersects the primary X-ray X1. Furthermore, a single sample can be transported.

[0038] The X-ray detector 2 uses an energy-dispersive X-ray detector, such as a semiconductor detector or a proportional counter tube. This X-ray detector 2 generates a charge proportional to the energy of a single incident X-ray photon, converts it into a voltage signal proportional to the charge, and then performs A / D conversion on the voltage signal to output it as a digital value. Alternatively, a wavelength-dispersive X-ray detector may be used.

[0039] Analyzer 5 is connected to X-ray detector 2 and analyzes the above-mentioned signal. Analyzer 5 is, for example, a waveform height analyzer (multi-channel analyzer) that obtains the waveform height of the voltage pulse from the above-mentioned signal and generates an energy spectrum. Analyzer 5 distinguishes the X-ray photon signals output from X-ray detector 2 by energy, counts the number of incidents according to energy, and obtains the energy spectrum as the X-ray intensity.

[0040] exist Figure 7 In the figure, the analyzer 5 discriminates by energy and counts the number of incidents by energy. Regarding X-ray intensity, multiple channels 42 are arranged, each of which divides the energy spectrum into equal intervals ΔE. The number of counts for each channel 42 is displayed. The time Tm for accumulating the incident counts is set as shown in the following equation 1.

[0041]

Formula 1

[0042] Tm <L / V

[0043] Here, L is the length of the measurement target portion of the sample S in the conveying direction D, and V is the conveying speed of the sample S. Here, as an example, Tm is set to 1 / 10 of L / V.

[0044] Furthermore, it is preferable that the time Tm for integrating the injection counts is shorter than the time required for the sample to pass through the X-ray irradiation unit.

[0045] The energy spectrum accumulation operation is continuously performed, and the obtained energy spectrum is stored as an array of energy spectra in the memory of the data processing unit 7. The data processing unit 7 determines whether the sample S moved by the sample transport unit 3 is passing through the irradiation position 6 based on the obtained energy spectrum and a set threshold.

[0046] In addition, the energy spectra stored in the memory of the data processing unit 7 are overwritten in order from old to new, so that the storage area will not be saturated. However, by installing the memory in a manner that allows a sufficient number of energy spectra to be written at one time, the memory will not be overwritten by the next energy spectrum within the time required for subsequent processing.

[0047] The analyzer 5 is a waveform height analyzer (multi-channel pulse height analyzer) that obtains the waveform height of a voltage pulse from the signal from the X-ray detection unit 2 and generates an energy spectrum.

[0048] The data processing unit 7 monitors the energy spectrum acquired successively, and detects changes in the energy spectrum due to the presence or absence of the sample S.

[0049] The following description will be made on the case where the main component of the material of the sample transport unit 3 is element A and the sample S contains element B as a main component. Figure 2 As shown in Figure 1 In this case, when the sample S is not located at the irradiation position 6, the horizontal axis represents energy and the vertical axis represents X-ray intensity. Since the surface of the sample transport unit 3 is located at the irradiation position 6, the energy spectrum 10 has a peak in X-ray intensity 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. Figure 4 As shown in Figure 3 The energy spectrum 12 when the sample S is located at the irradiation position 6 is shown in FIG. 1 . Since the sample S is located 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 in the X-ray intensity. Figure 4 The X-ray intensity of the fluorescent X-ray of element A is 11 times that of Figure 2 When I was young.

[0050] Utilizing this property, a predetermined X-ray intensity threshold 14 is set, and when the X-ray intensity of the energy 13 of the fluorescent X-ray of the element B, the main component of the sample S, exceeds the threshold 14 , it is determined that the sample S is present at the irradiation position 6 .

[0051] In this embodiment, since Tm is set to 1 / 10 of L / V as described above, Figure 5 As shown, energy spectra T1 to T21 continuously measured at predetermined time intervals while the sample S is being conveyed are shown.

[0052] exist Figure 5In the case of energy spectra T2 to T20, the X-ray intensity of the fluorescent X-rays of element B at energy 13 is greater than threshold value 14, and therefore, it is determined that the sample S is located at irradiation position 6. The determined X-ray intensity of energy 13 is analyzed as the measured energy spectrum of the sample. All of these continuous measured energy spectra are processed as separate energy spectra. Alternatively, as with energy spectra T2 and T20, the first and last measured energy spectra can be excluded, and T3 to T29 can be accumulated or averaged to be processed as a single energy spectrum. Alternatively, the center or center of gravity of the continuous measured energy spectra can be selected as the energy spectrum of the sample.

[0053] The X-ray analysis device of the present embodiment described above uses the X-ray intensity of the energy 13 of the fluorescent X-ray of the element B which is the main component of the sample S to determine whether the sample S is present at the irradiation position 6. However, the X-ray intensity and a specific threshold value may be used to determine the presence or absence of the sample based on the energy of the fluorescent X-ray of the element A which is the main component of the material of the sample transport part.

[0054] In addition, the threshold value in this case may be different from the threshold value in the present embodiment.

[0055] like Figure 2 and Figure 4 As shown, the X-ray intensity of the fluorescent X-ray energy 11 of element A, the material of the sample transport unit 3, also varies depending on the position of the sample S. When the sample S is at the irradiation position 6, the amount of X-rays X1 irradiating the sample transport unit 3 decreases, and the X-ray intensity of the fluorescent X-ray energy 11 of element A decreases significantly. By setting a specific threshold for element A and comparing the X-ray intensity of the fluorescent X-ray energy 11 of element A with this threshold, it is possible to determine whether the sample S is at the irradiation position 6.

[0056] Furthermore, in another embodiment of the X-ray analysis apparatus, when the surface of the sample transport portion 3 is made of plastic material, the efficiency of scattering the primary X-rays of the plastic is high, and the peaks of the fluorescent X-rays of carbon or oxygen, which are the main components of the plastic, are hardly detected. Therefore, when the sample S is not located at the irradiation position 6, as shown in FIG. Figure 6 As shown in the energy spectrum 15, the energy spectrum reflects the continuous X-ray component from the X-ray tube, with a significantly wider peak than the fluorescence X-ray peak. Utilizing this property, even when the X-ray intensity in energy region 16, where the intensity of scattered radiation is significant and does not interfere with the energy 13 of the main component element B of sample S, is below threshold 17, it can be determined whether the energy spectrum corresponds to the case where sample S is located at irradiation position 6.

[0057] Furthermore, in another embodiment of the X-ray analyzer, a case where the material of the sample S is not selected so that the fluorescent X-rays do not interfere with the fluorescent X-rays of the sample S, and a case where the composition of the sample S is unstable and it is difficult to set an appropriate threshold value is described. As a preparatory stage, a large number of energy spectra are acquired without placing the sample S. Subsequently, an energy spectrum is acquired when the sample is placed at or near the irradiation position.

[0058] When estimating differences in energy spectra between samples due to individual differences in sample composition, coating thickness, and other factors other than measurement system variations, it is important to include energy spectra of a large number of samples that appropriately reflect these individual differences. Deep learning is used to learn the differences in energy spectra between these two groups. Using the learning results obtained in the preparatory phase to date, it is determined whether this is the energy spectrum for when sample S is located at irradiation position 6.

[0059] like Figure 7 As shown in the figure, the energy spectrum generated by the X-ray detection unit 2 is an array of counts divided into energy ranges at equal intervals. In this case, the X-ray intensity of the fluorescent X-ray energy 11 of the main component of the material of the sample transport unit, that is, element A, is used as the energy E A0 ~E A1 Similarly, the X-ray intensity of the main component of the sample S, that is, the X-ray energy 13 of the element B, is also given as the value of the energy E B0 ~E B1 In the subsequent data processing, this method is meaningful when the peak shape of the energy spectrum is important. However, in the subsequent data processing, when the fluorescence X-ray intensity of each element is only E A0 ~E A1 Between and E B0 ~E B1 If the sum of the individual counts between the two is sufficient, there is no need to divide the channels into evenly spaced intervals to generate the energy spectrum. In this case, instead of dividing the channels into evenly spaced intervals, the energy region containing the peak energy of the necessary elements can be set as a number of channels, and the analyzers can be operated as multiple single-channel analyzers, thereby achieving the purpose of the present invention.

Claims

1. An X-ray analysis device, characterized in that: The X-ray analysis device comprises: an X-ray source capable of irradiating the sample with X-rays; a sample transporting unit configured to transport the sample; an X-ray detection unit that detects secondary X-rays generated from the sample transport unit; an analyzer that discriminates the signal output from the X-ray detection unit according to energy, counts the number of incidents according to energy, and obtains an energy spectrum as X-ray intensity; as well as a data processing unit that compares the secondary X-ray intensity of the energy of a specific element in the energy spectrum obtained by the analyzer with a threshold value of the secondary X-ray intensity set for the specific element of the surface material of the sample transport unit, thereby determining whether the sample moved by the sample transport unit is passing through the irradiation position of the X-rays. The analyzer continuously acquires an energy spectrum of X-ray intensities of secondary X-rays detected by the X-ray detection unit at time intervals shorter than a time required for the sample to pass through the irradiation position of the X-rays.

2. The X-ray analysis device according to claim 1, wherein The X-ray energy spectrum is composed of a histogram of X-ray counts obtained by dividing a continuous energy or wavelength range into equal intervals.

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