Thickness measurement method, x-ray analysis device, information processing device, and computer program

Abstract

Provided are a thickness measurement method, an X-ray analyzer, an information processing device, and a computer program with which it is possible to measure the thickness of more layers of samples than in the prior art. In the thickness measurement method, a sample including a first layer and a second layer that are stacked is irradiated with X-rays such that the X-rays pass through the first layer and the second layer in this order, fluorescent X-rays generated from the first layer are detected, transmitted X-rays after passing through the sample are detected, and the thickness of the sample is measured by elemental analysis based on the fluorescent X-rays. An absorption coefficient of X-rays in the first layer and a density of the first layer are determined, and a thickness of the first layer is calculated based on intensities at two different energies of the transmitted X-rays, the absorption coefficient, and the density.

Description

Technical Field

[0001] The present invention relates to a thickness measurement method, an X-ray analysis device, an information processing device, and a computer program for measuring the thickness of a specific layer included in a multi-layer sample. Background Art

[0002] Sometimes, it is desirable to measure the thickness of each layer included in a multilayer sample. For example, sometimes, it is desirable to measure the thickness of a covering film covering a substrate. As a method for measuring the thickness of each layer of a multilayer sample, there is a method of irradiating the multilayer sample with X-rays, detecting fluorescent X-rays generated from the multilayer sample, and measuring the thickness of each layer based on the fluorescent X-rays. In addition, there is a method of detecting transmitted X-rays after passing through the multilayer sample, and measuring the thickness of each layer based on the transmitted X-rays. Patent Document 1 discloses a technique for measuring the thickness of a sample based on transmitted X-rays. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Publication No. 11-287643 Summary of the invention Technical Problems to be Solved by the Invention

[0004] In the method of measuring thickness based on fluorescent X-rays, the intensity of fluorescent X-rays generated from the part far from the surface becomes smaller, so there is a limit to the thickness that can be measured. The information related to the transmission X-rays after passing through the multi-layer sample becomes an overlap of the information related to the multiple layers. Therefore, the method of measuring thickness based on transmission X-rays requires that the composition of each layer is known. In this way, in the previous method, the sample whose thickness can be measured is limited. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thickness measurement method, an X-ray analysis device, an information processing device, and a computer program capable of measuring the thickness of more multilayer samples than before. Technical solutions for solving technical problems

[0005] A thickness measurement method according to one embodiment of the present invention is characterized in that a sample including a stacked first layer and a second layer is irradiated with X-rays in a manner that the X-rays pass through the first layer and the second layer in that order, fluorescent X-rays generated from the first layer are detected, transmitted X-rays after passing through the sample are detected, an absorption coefficient of X-rays in the first layer and a density of the first layer are determined by elemental analysis based on the fluorescent X-rays, and the thickness of the first layer is calculated based on the intensities of the transmitted X-rays at two different energies, the absorption coefficient and the density.

[0006] In one embodiment of the present invention, a sample including a first layer and a second layer stacked together is irradiated with X-rays, fluorescent X-rays and transmitted X-rays are detected, and the absorption coefficient of X-rays in the first layer and the density of the first layer are determined based on the fluorescent X-rays. In addition, the thickness of the first layer is calculated based on the intensity of the transmitted X-rays at two energies, the absorption coefficient of X-rays in the first layer, and the density of the first layer. By using the detection results of both the fluorescent X-rays and the transmitted X-rays, the thickness of the first layer can be measured for a sample different from the conventional one. By calculating the thickness of the first layer using the characteristics of the first layer analyzed based on the detection results of the fluorescent X-rays, the thickness of the first layer can be measured even for a sample whose composition of the first layer is unclear.

[0007] A thickness measurement method according to one aspect of the present invention is characterized in that the difference between the two energies is within a predetermined range.

[0008] In one embodiment of the present invention, in order to calculate the thickness of the first layer, the two energies are determined using the intensities of the transmitted X-rays at two energies so that the difference between the two energies is within a specified range. Since the difference between the two energies is small, the intensities of the X-rays irradiated to the sample at each energy are substantially the same, and the formula for calculating the thickness of the first layer can be approximated by omitting the intensity ratio of the two energies of the X-rays irradiated to the sample included in the formula.

[0009] The thickness measurement method according to one embodiment of the present invention is characterized in that an absorption edge of the element included in the second layer is not included in an energy range between the two energies.

[0010] In one embodiment of the present invention, the difference between the two energies is small, and the position of the absorption edge of the element contained in the second layer is not included in the energy range between the two energies. Therefore, the absorption coefficient of the X-ray in the second layer is approximately the same. The formula for calculating the thickness of the first layer can be approximated by omitting the term obtained by multiplying the density of the second layer and the thickness of the second layer by the difference in the absorption coefficient of the X-ray of the two energies in the second layer. By using the approximated formula, the thickness of the first layer can be calculated even if the composition or thickness of the second layer is unclear.

[0011] The thickness measurement method according to one embodiment of the present invention is characterized in that the two energies are determined by elemental analysis using the fluorescent X-rays so that an absorption edge of the element contained in the first layer is included in an energy range between the two energies.

[0012] In one embodiment of the present invention, the position of the absorption edge of the element contained in the first layer is included in the energy range between the two energies. Therefore, the difference in the intensity of the transmitted X-ray at the two energies becomes larger, and the difference in the absorption coefficient of the X-ray at the two energies in the first layer also becomes larger. In the formula for calculating the thickness of the first layer, the ratio of the logarithm of the ratio of the intensity of the transmitted X-ray at the two energies to the difference in the absorption coefficient of the X-ray at the two energies in the first layer is included. The calculation result of the formula will not be incorrect, and the thickness of the first layer can be correctly calculated.

[0013] An X-ray analysis device according to one embodiment of the present invention is characterized in that it comprises: an irradiation unit for irradiating a sample including a stacked first layer and a second layer with X-rays in a manner that the X-rays pass through the first layer and the second layer in that order; a fluorescence X-ray detector for detecting the fluorescence X-rays generated from the first layer; a transmission X-ray detector for detecting the transmission X-rays after passing through the sample; and an analysis unit for determining an absorption coefficient of X-rays in the first layer and a density of the first layer by elemental analysis based on the fluorescence X-rays, and for calculating a thickness of the first layer based on the intensities of the transmission X-rays at two different energies, the absorption coefficient, and the density.

[0014] In one embodiment of the present invention, an X-ray analyzer irradiates a sample including a first layer and a second layer stacked together with X-rays, detects fluorescent X-rays and transmitted X-rays, and determines the absorption coefficient of X-rays in the first layer and the density of the first layer by elemental analysis based on the fluorescent X-rays. In addition, the X-ray analyzer calculates the thickness of the first layer based on the intensity of the transmitted X-rays at two energies, the absorption coefficient of X-rays in the first layer, and the density of the first layer. By calculating the thickness of the first layer using the characteristics of the first layer analyzed based on the detection results of the fluorescent X-rays, the thickness of the first layer can be measured even for a sample whose composition of the first layer is unclear.

[0015] In the X-ray analysis device according to one aspect of the present invention, the analysis unit calculates the thickness of the first layer by elemental analysis based on the fluorescent X-rays instead of using the detection result of the transmission X-rays.

[0016] In one embodiment of the present invention, an X-ray analyzer can measure the thickness of a first layer included in a sample based only on the detection result of fluorescent X-rays without using the detection result of transmitted X-rays. When the thickness of the first layer is relatively small, the X-ray analyzer can simply measure the thickness of the first layer based only on the detection result of fluorescent X-rays. When the thickness of the first layer is relatively large, the X-ray analyzer can measure the thickness of the first layer by using the detection results of both fluorescent X-rays and transmitted X-rays.

[0017] An information processing device according to one embodiment of the present invention is characterized in that it comprises: an acquisition unit for acquiring detection results of fluorescent X-rays generated from a sample including a first layer and a second layer stacked together by irradiating the X-rays to the first layer in a manner that the X-rays pass through the first layer and the second layer in that order, and detection results of transmitted X-rays after passing through the sample; a determination unit for determining an absorption coefficient of X-rays in the first layer and a density of the first layer by elemental analysis based on the detection results of the fluorescent X-rays; and a calculation unit for calculating the thickness of the first layer based on the intensities of the transmitted X-rays at two different energies, the absorption coefficient and the density.

[0018] A computer program according to one embodiment of the present invention is characterized in that the computer program causes the computer to execute the following processing: performing elemental analysis based on detection results of fluorescent X-rays generated from the first layer by irradiating a sample including a stacked first layer and a second layer with X-rays in a manner such that the X-rays pass through the first layer and the second layer in that order, thereby determining an absorption coefficient of the X-rays in the first layer and a density of the first layer, and calculating a thickness of the first layer based on the intensities of the transmitted X-rays at two different energies contained in the detection results of the transmitted X-rays after passing through the sample, the absorption coefficient, and the density.

[0019] In one embodiment of the present invention, based on the fluorescent X-rays detected by irradiating X-rays to a sample including a stacked first layer and a second layer, the absorption coefficient of the X-rays in the first layer and the density of the first layer are determined by information processing. In addition, based on the intensities of the two energies of the detected transmission X-rays, the absorption coefficient of the X-rays in the first layer, and the density of the first layer, the thickness of the first layer is calculated by information processing. By calculating the thickness of the first layer using the characteristics of the first layer analyzed based on the detection results of the fluorescent X-rays, the thickness of the first layer can be measured even for a sample whose composition of the first layer is unclear. Effects of the Invention

[0020] In the present invention, a greater thickness than before can be measured, and the thickness of the first layer can be measured even for a sample whose composition of the first layer is unclear. Therefore, the thickness of the first layer included in more multilayer samples than before can be measured, and the present invention has an excellent effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a block diagram showing an example of the functional configuration of an X-ray analysis device. Figure 2 This is a block diagram showing an example of the internal configuration of the analysis unit. Figure 3is a schematic cross-sectional view of the specimen. Figure 4 This is a diagram showing an example of a spectrum of transmitted X-rays. Figure 5 1 is a flowchart showing an example of the steps of a process for measuring the thickness of the first layer performed by the X-ray analysis device. Figure 6 This is a flowchart showing an example of the steps of a process executed by the X-ray analysis apparatus according to the second embodiment for measuring the thickness of the first layer based on fluorescent X-rays. DETAILED DESCRIPTION

[0022] Hereinafter, the present invention will be described in detail based on the drawings showing embodiments of the present invention. <Implementation Method 1> Figure 1 1 is a block diagram showing an example of the functional configuration of an X-ray analyzer 100. The X-ray analyzer 100 includes: an irradiation unit 21 for irradiating a sample 3 with X-rays; a fluorescent X-ray detector 22 for detecting fluorescent X-rays generated from the sample 3 irradiated with X-rays; and a transmission X-ray detector 23 for detecting transmission X-rays after passing through the sample 3. The sample 3 is a multilayer sample including a plurality of stacked layers. The X-ray analyzer 100 performs a thickness measurement method for measuring the thickness of a layer included in the sample 3. The irradiation unit 21 includes an X-ray source for generating X-rays. The X-ray source is, for example, an X-ray tube. Figure 1 In the figure, arrows are used to indicate the X-rays, fluorescent X-rays, and transmitted X-rays irradiated to the sample 3 .

[0023] The fluorescent X-ray detector 22 and the transmission X-ray detector 23 are radiation detectors having radiation detection elements formed using semiconductors. For example, the fluorescent X-ray detector 22 and the transmission X-ray detector 23 are SDDs (Silicon Drift Detectors). The fluorescent X-ray detector 22 is arranged so as to face the surface of the sample 3 that is irradiated with X-rays. By irradiating the sample 3 with X-rays from the irradiation unit 21, fluorescent X-rays are generated in the sample 3. The fluorescent X-rays are radiated from the surface of the sample 3 and enter the fluorescent X-ray detector 22. The fluorescent X-ray detector 22 detects the incident fluorescent X-rays and outputs a signal of an intensity corresponding to the energy of the fluorescent X-rays.

[0024] The transmission X-ray detector 23 is arranged at a position opposite to the irradiation unit 21. In a state where the sample 3 is arranged between the irradiation unit 21 and the transmission X-ray detector 23, the sample 3 is irradiated with X-rays from the irradiation unit 21. A part of the X-rays irradiated from the irradiation unit 21 to the sample 3 passes through the sample 3. The X-rays that have passed through the sample 3 are called transmission X-rays. The transmission X-rays are incident on the transmission X-ray detector 23. The transmission X-ray detector 23 detects the incident transmission X-rays and outputs a signal of an intensity corresponding to the energy of the transmission X-rays.

[0025] The fluorescent X-ray detector 22 is connected to a first signal processing unit 24, and the transmission X-ray detector 23 is connected to a second signal processing unit 25. The first signal processing unit 24 and the second signal processing unit 25 are connected to the analysis unit 1. The analysis unit 1 is configured using a computer. The analysis unit 1 is connected to a display unit 27 such as a liquid crystal display or an EL display (Electroluminescent Display). The irradiation unit 21, the first signal processing unit 24, the second signal processing unit 25, and the analysis unit 1 are connected to a control unit 26.

[0026] The control unit 26 controls the operation of the irradiation unit 21, the first signal processing unit 24, the second signal processing unit 25, and the analysis unit 1. The control unit 26 is configured using a computer including a computing unit that performs operations for controlling each unit. The control unit 26 may be configured to receive an operation from a user and control each unit of the X-ray analysis device 100 according to the received operation. The control unit 26 and the analysis unit 1 may also be configured integrally.

[0027] The fluorescent X-ray detector 22 outputs a signal having an intensity corresponding to the energy of the fluorescent X-ray, and the first signal processing unit 24 receives the signal output by the fluorescent X-ray detector 22. The first signal processing unit 24 detects the intensity of the received signal to detect a signal value corresponding to the energy of the fluorescent X-ray detected by the fluorescent X-ray detector 22. The first signal processing unit 24 counts the signal according to the signal value, and outputs data indicating the relationship between the signal value and the count value to the analysis unit 1.

[0028] The transmission X-ray detector 23 outputs a signal having an intensity corresponding to the energy of the transmission X-ray, and the second signal processing unit 25 receives the signal output by the transmission X-ray detector 23. The second signal processing unit 25 detects the intensity of the received signal to detect a signal value corresponding to the energy of the transmission X-ray detected by the transmission X-ray detector 23. The second signal processing unit 25 counts the signal according to the signal value, and outputs data indicating the relationship between the signal value and the count value to the analysis unit 1.

[0029] The analysis unit 1 receives data indicating the relationship between the signal value and the count value output by the first signal processing unit 24. The analysis unit 1 generates a spectrum of the fluorescent X-ray detected by the fluorescent X-ray detector 22 based on the data from the first signal processing unit 24. The signal value corresponds to the energy of the fluorescent X-ray, and the count value corresponds to the number of times the fluorescent X-ray is detected, that is, the intensity of the fluorescent X-ray. Therefore, based on the relationship between the signal value and the count value, a spectrum of the fluorescent X-ray indicating the relationship between the energy and the intensity of the fluorescent X-ray is obtained.

[0030] In addition, the analysis unit 1 receives data indicating the relationship between the signal value and the count value output by the second signal processing unit 25. The analysis unit 1 generates a spectrum of the transmitted X-ray detected by the transmission X-ray detector 23 based on the data from the second signal processing unit 25. The signal value corresponds to the energy of the transmitted X-ray, and the count value corresponds to the number of times the transmitted X-ray is detected, that is, the intensity of the transmitted X-ray. Therefore, based on the relationship between the signal value and the count value, a spectrum of the transmitted X-ray indicating the relationship between the energy and the intensity of the transmitted X-ray is obtained.

[0031] The process of counting the signals outputted by the fluorescent X-ray detector 22 and the transmission X-ray detector 23 according to the signal values ​​may be performed by the analysis unit 1 instead of the first signal processing unit 24 and the second signal processing unit 25. The generation of the spectrum of the fluorescent X-ray may be performed by the first signal processing unit 24, and the generation of the spectrum of the transmission X-ray may be performed by the second signal processing unit 25. The analysis unit 1 stores spectral data representing the spectrum of the fluorescent X-ray and spectral data representing the spectrum of the transmission X-ray. The display unit 27 displays the spectrum of the fluorescent X-ray or the transmission X-ray. The user can confirm the spectrum of the fluorescent X-ray from the sample 3 or the spectrum of the transmission X-ray after passing through the sample 3. In addition, the analysis unit 1 performs information processing based on the spectrum of the fluorescent X-ray and the transmission X-ray. More specifically, the analysis unit 1 performs information processing in order to measure the thickness of the layer included in the sample 3. The analysis unit 1 corresponds to an information processing device that performs information processing for measuring the thickness of the layer included in the sample 3.

[0032] Figure 21 is a block diagram showing an example of the internal structure of the analysis unit 1. The analysis unit 1 is composed of a computer such as a personal computer. The analysis unit 1 includes a computing unit 11, a memory 12, a reading unit 13, a storage unit 14, and an operating unit 15. The computing unit 11 is composed of, for example, a CPU (central processing unit), a GPU (graphics processing unit), or a multi-core CPU. The computing unit 11 can also be composed of a quantum computer. The memory 12 stores temporary data generated by calculations. The memory 12 is, for example, a RAM (Random Access Memory). The reading unit 13 reads information from a recording medium 10 such as an optical disk or a removable memory. The storage unit 14 is non-volatile, for example, a hard disk or a non-volatile semiconductor memory. The operating unit 15 receives input of information such as text by receiving operations from the user. The operating unit 15 is, for example, a touch panel, a keyboard, or a pointing device. The user inputs various instructions to the analysis unit 1 by operating the operating unit 15. The analysis unit 1 receives instructions input using the operating unit 15.

[0033] The operation unit 11 causes the reading unit 13 to read the computer program 141 recorded on the recording medium 10, and stores the read computer program 141 in the storage unit 14. The operation unit 11 executes the processing required by the analysis unit 1 according to the computer program 141. In addition, the computer program 141 may also be downloaded from the outside of the analysis unit 1. Alternatively, the computer program 141 may also be stored in the analysis unit 1 in advance. In these cases, the analysis unit 1 may not have the reading unit 13. In addition, the analysis unit 1 may also be composed of a plurality of computers.

[0034] The analysis unit 1 is connected to a display unit 27, a first signal processing unit 24, a second signal processing unit 25, and a control unit 26. The display unit 27 displays an image. The analysis unit 1 outputs information required for information processing by causing the display unit 27 to display an image containing information. The analysis unit 1 receives signals from the first signal processing unit 24 and the second signal processing unit 25, and receives control signals from the control unit 26. In addition, the analysis unit 1 and the control unit 26 may be composed of the same computer.

[0035] The storage unit 14 stores an element database, which records data required for element analysis. Information representing the characteristics of multiple elements is recorded in the element database. For example, the element database records the position of the peak contained in the fluorescence X-ray spectrum of each element, the intensity ratio of multiple peaks, the position of the absorption edge, the mass absorption coefficient, and the density. The position of the peak and the position of the absorption edge are represented by the energy of the X-ray. In addition, the element database can also be set outside the analysis unit 1. For example, the element database is stored in a storage device connected to the analysis unit 1 via a communication network. The element database can also be constructed using a cloud. The operation unit 11 accesses the element database via the communication network and performs processing with reference to the data recorded in the element database.

[0036] Figure 3 3 is a schematic cross-sectional view of the sample 3. The sample 3 is composed of a first layer 31 and a second layer 32 stacked together. The thickness of the first layer 31 is set to t1, and the thickness of the second layer 32 is set to t2. For example, the second layer 32 is a base material, and the first layer 31 is a covering film covering the base material. For example, the sample 3 is a part of a plate-shaped raw material. The analysis unit 1 performs information processing for measuring the thickness of the first layer 31 included in the sample 3. Figure 3 As shown, the sample 3 is irradiated with X-rays in such a manner that the X-rays are transmitted in the order of the first layer 31 and the second layer 32. Fluorescent X-rays are generated from the first layer 31 irradiated with X-rays. The fluorescent X-rays detected by the fluorescent X-ray detector 22 are mainly fluorescent X-rays generated from the first layer 31. The fluorescent X-rays generated from the second layer 32 are absorbed by the first layer 31 and are hardly detected by the fluorescent X-ray detector 22.

[0037] Figure 4 This is a diagram showing an example of a spectrum of transmitted X-rays. Figure 4 The horizontal axis represents the energy of the transmitted X-ray, and the vertical axis represents the intensity of the transmitted X-ray. For example, the intensity of the X-ray is represented by the count value per unit time. Two different energies of the transmitted X-rays for obtaining the spectrum are set as E1 and E2. Both the energies E1 and E2 are different from the energy of the peak of the spectrum of the fluorescent X-ray generated from the first layer 31. In addition, both the energies E1 and E2 are different from the absorption edge of the element contained in the first layer 31 or the second layer 32.

[0038] like Figure 3 As shown in FIG. 1 , the intensity of the X-ray irradiated to the sample 3 at energy E1 is denoted as I0(E1), and the intensity at energy E2 is denoted as I0(E2). The X-ray intensities I0(E1) and I0(E2) are the intensities before the X-ray enters the sample 3. The intensity of the detected fluorescent X-ray at energy E1 is denoted as I0(E1). F (E1), set the intensity at energy E2 to I F (E2). The intensity of the detected transmitted X-ray at energy E1 is set to I T (E1), set the intensity at energy E2 to I T (E2).

[0039] The mass absorption coefficient of X-rays at energy E1 of the first layer 31 is set to μ1(E1), and the mass absorption coefficient of X-rays at energy E2 is set to μ1(E2). The mass absorption coefficient of X-rays at energy E1 of the second layer 32 is set to μ2(E1), and the mass absorption coefficient of X-rays at energy E2 is set to μ2(E2). The density of the first layer 31 is set to ρ1, and the density of the second layer 32 is set to ρ2. The transmittance of X-rays at energy E1 of the sample 3 is set to T(E1), and the transmittance of X-rays at energy E2 is set to T(E2). The transmittances T(E1) and T(E2) are expressed by the following equations (1) and (2). ln(T(E1))=ln(I T (E1) / I0(E1))=-μ1(E1)ρ1t1-μ2(E1)ρ2t2……(1) ln(T(E2))=ln(I T (E2) / I0(E2))=-μ1(E2)ρ1t1-μ2(E2)ρ2t2……(2)

[0040] By subtracting equation (1) from equation (2), the following equation (3) is obtained. ln(T(E1))-ln(T(E2)) =ln(I T (E1) / I0(E1))-ln(I T (E2) / I0(E2)) =-(μ1(E1)ρ1t1+μ2(E1)ρ2t2)+(μ1(E2)ρ1t1+μ2(E2)ρ2t2) ln(T(E1) / T(E2)) =ln({I T (E1) / I T (E2)}·{I0(E2) / I0(E1)} =(μ1(E2)-μ1(E1))ρ1t1+(μ2(E2)-μ2(E1))ρ2t2……(3)

[0041] Here, it is assumed that E2=E1+ΔE and ΔE≈0. That is, it is assumed that energy E2 is a value very close to energy E1. At this time, the intensities of the X-rays irradiated to the sample 3 at energies E1 and E2 are approximately the same, that is, I0(E1)≈I0(E2). In addition, it is assumed that the absorption edge of the elements contained in the second layer 32 is not included in the energy range between energy E1 and energy E2. In this case, the mass absorption coefficients of the X-rays at energies E1 and E2 of the second layer 32 are approximately the same, that is, μ2(E1)≈μ2(E2). Based on equation (3), the following equation (4) is obtained. ln(T(E1) / T(E2))≈ln(I T (E1) / I T (E2))≈(μ1(E2)-μ1(E1))ρ1t1……(4)

[0042] From equation (4), the following equation (5) is obtained as an equation for calculating the thickness t1 of the first layer 31 . t1≈ln(I T (E1) / I T (E2)) / {(μ1(E2)-μ1(E1))ρ1}......(5)

[0043] By using equation (5), the thickness t1 of the first layer 31 can be calculated. The intensity I of the transmitted X-ray T (E1) and I T (E2) is obtained from the spectrum of the transmitted X-ray. When the absorption edge of the element contained in the first layer 31 is included in the energy range between energy E1 and energy E2, the intensity I of the transmitted X-ray is T (E1) and I T As the difference between μ1(E2) and μ1(E2) increases, the difference between the X-ray mass absorption coefficient μ1(E2) and μ1(E1) of the first layer 31 also increases.

[0044] When the thickness t1 of the first layer 31 is calculated using equation (5), the intensities I0(E1) and I0(E2) of the X-rays irradiated to the sample 3 are not used in the calculation. Therefore, it is not necessary to obtain the X-rays irradiated to the sample 3. In addition, the mass absorption coefficients μ2(E1) and μ2(E2) of the X-rays of the second layer 32, the density ρ2 of the second layer 32, and the thickness t2 of the second layer 32 are not used in the calculation. Therefore, even if the composition or thickness t2 of the second layer 32 is unknown, the thickness t1 of the first layer 31 can be calculated.

[0045] Figure 5 1 is a flowchart showing an example of the steps of the process for measuring the thickness t1 of the first layer 31 performed by the X-ray analyzer 100. The steps are hereinafter referred to as S. The operation unit 11 performs information processing according to the computer program 141, whereby the analysis unit 1 performs the process. The irradiation unit 21 generates X-rays and irradiates the sample 3 with the X-rays (S101). The sample 3 is held in the X-ray analyzer 100 in a manner that allows the X-rays to pass through the first layer 31 and the second layer 32 in this order. Fluorescent X-rays are generated from the first layer 31 by the irradiation of X-rays. The fluorescent X-ray detector 22 detects the fluorescent X-rays (S102). The transmission X-ray detector 23 detects the transmission X-rays that have passed through the sample 3 (S103).

[0046] The fluorescent X-ray detector 22 outputs a signal of intensity corresponding to the energy of the fluorescent X-ray to the first signal processing unit 24, and the first signal processing unit 24 counts the signal according to the signal value, and outputs data indicating the relationship between the signal value and the count value to the analysis unit 1. The transmission X-ray detector 23 outputs a signal of intensity corresponding to the energy of the transmission X-ray to the second signal processing unit 25, and the second signal processing unit 25 counts the signal according to the signal value, and outputs data indicating the relationship between the signal value and the count value to the analysis unit 1. The analysis unit 1 obtains the detection results of the fluorescent X-ray and the transmission X-ray by receiving the data from the first signal processing unit 24 and the second signal processing unit 25 (S104). The analysis unit 1 generates spectra of the fluorescent X-ray and the transmission X-ray, and stores the spectral data in the storage unit 14. The processing of S104 corresponds to the acquisition unit.

[0047] The analysis unit 1 determines the elements contained in the first layer 31 by performing element analysis based on the spectrum of the fluorescent X-ray (S105). In S105, for example, the operation unit 11 determines the position of the peak contained in the spectrum of the fluorescent X-ray and the intensity ratio of multiple peaks, retrieves the element whose peak position and the intensity ratio of multiple peaks are consistent from the element database, and determines the element. When the first layer 31 contains multiple elements, the operation unit 11 determines the multiple elements.

[0048] The analysis unit 1 determines two energies E1 and E2 (S106). In S106, the operation unit 11 determines E1 and E2 as energies different from the positions of peaks included in the spectrum of fluorescent X-rays. The operation unit 11 determines the energies E1 and E2 so that the positions of the absorption edges of the elements included in the first layer 31 recorded in the element database are included in the energy range between E1 and E2. In addition, the operation unit 11 determines the energies E1 and E2 so that the difference between the two energies E1 and E2 is included in a prescribed range. The prescribed range is a small range in which the intensities I0(E1) and I0(E2) of the X-rays irradiated to the sample 3 are approximately the same. For example, the operation unit 11 determines the energies E1 and E2 so that the absolute value of the difference between E1 and E2 is below a prescribed threshold. The threshold is pre-stored in the storage unit 14.

[0049] In S106, the calculation unit 11 determines the energies E1 and E2 within the highest possible energy range. The higher the energy of the X-ray, the easier it is for the X-ray to pass through the sample 3, and the greater the intensity of the transmitted X-ray. The intensity I of the detected transmitted X-ray T (E1) and I T (E2) becomes larger, and the SN ratio (signal-to-noise ratio) becomes larger.

[0050] When the element included in the second layer 32 is identified, the operation unit 11 determines the energies E1 and E2 so that the position of the absorption edge of the element included in the second layer 32 is not included in the energy range between E1 and E2. In this case, the position of the absorption edge of the element included in the second layer 32 is stored in the storage unit 14. Alternatively, the information indicating the element included in the second layer 32 is stored in the storage unit 14, and the operation unit 11 determines the position of the absorption edge with reference to the element database. Alternatively, the position of the absorption edge of the element included in the second layer 32 or the information indicating the element included in the second layer 32 may be input to the analysis unit 1 by the user operating the operation unit 15.

[0051] In S106, the operation unit 11 selects two energies E1 and E2 that meet the conditions from the energies of the detected transmitted X-rays, thereby determining E1 and E2. The combination of the two energies E1 and E2 may be pre-stored in the storage unit 14, and the operation unit 11 may determine the two energies E1 and E2 by selecting a combination that meets the conditions from the stored multiple combinations. Alternatively, the user may input the values ​​of the two energies E1 and E2 by operating the operation unit 15, and the operation unit 11 may determine the two energies E1 and E2 by obtaining the input values ​​of E1 and E2.

[0052] The analysis unit 1 determines the mass absorption coefficients μ1(E1) and μ1(E2) of X-rays of the first layer 31 and the density ρ1 of the first layer 31 by elemental analysis (S107). When the element contained in the first layer 31 is a single element, the calculation unit 11 obtains the mass absorption coefficients μ1(E1) and μ1(E2) and the density ρ1 of the element contained in the first layer 31 from the element database in S107.

[0053] In the case where the first layer 31 contains a plurality of elements, in S107, the operation unit 11 determines the content ratio of the plurality of elements based on the spectrum of the fluorescent X-ray. For example, the operation unit 11 determines the content ratio of the plurality of elements based on the intensity ratio of the peaks caused by each element. By determining the content ratio of the plurality of elements, the operation unit 11 determines the composition of the first layer 31. The operation unit 11 determines the mass absorption coefficient at the energies E1 and E2 and the density of the first layer 31 according to the composition of the first layer 31. For example, the operation unit 11 calculates the weighted average of the mass absorption coefficients at the energies E1 and E2 of the plurality of elements recorded in the element database according to the content ratio of the plurality of elements, thereby calculating the mass absorption coefficients μ1(E1) and μ1(E2) of the X-ray of the first layer 31. Similarly, the operation unit 11 calculates the weighted average of the densities of the plurality of elements recorded in the element database according to the content ratio of the plurality of elements, thereby calculating the density ρ1 of the first layer 31. Alternatively, the calculation unit 11 may determine the density ρ1 by acquiring the density associated with the composition of the first layer 31 from a database that associates the composition of a substance with the density. The process of S107 corresponds to a determination unit.

[0054] The analysis unit 1 analyzes the intensity I of the transmitted X-rays at two energies E1 and E2. T (E1) and I T In S108, the operation unit 11 reads the intensity of the transmitted X-ray at the energy E1 and E2 from the spectrum of the transmitted X-ray and determines the intensity I of the transmitted X-ray. T (E1) and I T (E2) The processes of S105 to S108 may be performed in another order.

[0055] The calculation unit 11 calculates the thickness t1 of the first layer 31 (S109). In S109, the calculation unit 11 calculates the mass absorption coefficients μ1(E1) and μ1(E2) of the X-rays of the first layer 31, the density ρ1 of the first layer 31, and the intensity I T (E1) and I T (E2) Substituting into equation (5), the calculation shown in equation (5) is performed to calculate the thickness t1 of the first layer 31. The process of S109 corresponds to the calculation unit. Through the processes of S101 to S109, the X-ray analysis device 100 measures the thickness t1 of the first layer 31.

[0056] The analysis unit 1 outputs the calculated thickness t1 of the first layer 31 (S110). In S110, the operation unit 11 causes the display unit 27 to display the calculated value of the thickness t1 of the first layer 31, thereby outputting the thickness t1. The operation unit 11 stores the thickness t1 of the first layer 31 in the storage unit 14. After S110 ends, the analysis unit 1 ends the process for measuring the thickness t1 of the first layer 31.

[0057] As described in detail above, the X-ray analysis device 100 irradiates the sample 3 with X-rays, detects fluorescent X-rays and transmitted X-rays, and calculates the thickness t1 of the first layer 31 using the mass absorption coefficient of X-rays in the first layer 31 determined based on the fluorescent X-rays and the density of the first layer 31, and the intensity of the transmitted X-rays. In the conventional technology that uses only the detection results of fluorescent X-rays, there is a limit to the thickness that can be measured. In contrast, in the present embodiment, by using the detection results of fluorescent X-rays and transmitted X-rays, a greater thickness can be measured. In addition, in the present embodiment, the characteristics of the first layer 31 such as the mass absorption coefficient of X-rays are analyzed based on the detection results of fluorescent X-rays, and the thickness t1 of the first layer 31 is calculated using the analyzed characteristics of the first layer 31, so that even for the sample 3 whose composition of the first layer 31 is unknown, the thickness of the first layer 31 can be measured. Therefore, the thickness of the first layer 31 can be measured for more multi-layer samples than before.

[0058] In this embodiment, the intensities of the transmitted X-rays at two energies E1 and E2 are used to determine the energies E1 and E2 so that the difference between the two energies E1 and E2 is contained within a smaller specified range. By making the difference between the two energies E1 and E2 small, the intensities I0(E1) and I0(E2) of the X-rays irradiated to the sample 3 are approximately the same, and the formula (3) can be approximated by omitting I0(E2) / I0(E1) included in the formula (3) for calculating the thickness t1 of the first layer 31. As a result, the calculation of the thickness t1 of the first layer 31 is simplified, and there is no need to measure the intensities I0(E1) and I0(E2) of the X-rays before they are incident on the sample 3. Therefore, the measurement of the thickness t1 of the first layer 31 is simplified.

[0059] In the present embodiment, the position of the absorption edge of the element included in the second layer 32 is not included in the energy range between the two energies E1 and E2. Since the difference between the two energies E1 and E2 is small and the position of the absorption edge of the element included in the second layer 32 is not included between E1 and E2, the mass absorption coefficients μ2(E1) and μ2(E2) of the X-rays in the second layer 32 are substantially the same. Therefore, the formula (3) can be approximated by omitting the terms of multiplying the density ρ2 of the second layer 32 and the thickness t2 of the second layer 32 by the difference between μ2(E1) and μ2(E2) included in the formula (3) for calculating the thickness t1 of the first layer 31. As a result, the thickness t1 of the first layer 31 can be calculated using the formula (5) obtained by approximating the formula (3). By using the formula (5), the thickness t1 of the first layer 31 can be calculated regardless of the characteristics of the second layer 32. Therefore, even if the composition or thickness of the second layer 32 is unknown, the thickness t1 of the first layer 31 can be measured.

[0060] In this embodiment, the energy range between the two energies E1 and E2 includes the position of the absorption edge of the element contained in the first layer 31. Therefore, the intensity I of the transmitted X-ray is T (E1) and I T As the difference between the energies E1 and E2 increases, the difference between the mass absorption coefficients μ1(E2) and μ1(E1) of the X-rays of the first layer 31 also increases. When the absorption edge is not included between the energies E1 and E2, the intensity I of the transmitted X-rays T (E1) and I T (E2) is approximately the same, and the mass absorption coefficient μ1(E2) and μ1(E1) are also approximately the same. In this case, equation (5) becomes an equation of dividing a value close to zero by a value close to zero, and the calculation result of equation (5) may be incorrect. In this embodiment, since the intensity I of the transmitted X-ray is T (E1) and I T Since the difference between μ1(E2) and μ1(E1) is large, the difference between the mass absorption coefficients μ1(E2) and μ1(E1) is also large, and therefore the calculation result of formula (5) is correct. The thickness t1 of the first layer 31 can be correctly calculated using formula (5).

[0061] In this embodiment, the two energies E1 and E2 are in a high energy range. The higher the energy of the X-ray, the easier it is for the X-ray to pass through the sample 3. Therefore, even when the thickness of the sample 3 is large, the transmitted X-ray can be detected. Therefore, even when the thickness of the sample 3 is large, the thickness t1 of the first layer 31 can be measured. In addition, by making the energies E1 and E2 in a high energy range, the intensity I of the transmitted X-ray is T (E1) and I T(E2) increases, and the SN ratio increases. By utilizing the intensity of the transmitted X-ray having a large SN ratio, the thickness t1 of the first layer 31 can be measured with high accuracy.

[0062] In the first embodiment, an example of using equation (5) to calculate the thickness t1 of the first layer 31 is mainly shown, but the X-ray analysis device 100 may also be a method of calculating the thickness t1 of the first layer 31 using other equations. For example, the X-ray analysis device 100 may be a method of calculating the thickness t1 of the first layer 31 using equation (3). In this method, the composition and thickness of the second layer 32 are clear, and the mass absorption coefficient μ2(E1) and μ2(E2) of the X-rays in the second layer 32, the density ρ2 of the second layer 32, and the thickness t2 of the second layer 32 are stored in the storage unit 14. The analysis unit 1 uses the information stored in the storage unit 14 to calculate the thickness t1 of the first layer 31 according to equation (3). In this method, the difference between the two energies E1 and E2 may not be included in the prescribed range. In this method, the energy range between the two energies E1 and E2 may include the position of the absorption edge of the element included in the second layer 32, and may not include the position of the absorption edge of the element included in the first layer 31. The X-ray analysis device 100 can also perform processing using two energies E1 and E2 in a relatively low energy range.

[0063] In the first embodiment, an example in which the sample 3 is composed of the first layer 31 and the second layer 32 is shown, but the X-ray analysis device 100 may also be a method of measuring the thickness of the first layer 31 included in the sample 3 including three or more layers stacked. For example, when the first layer 31 is covered with a thinner surface layer, the X-ray analysis device 100 may calculate the thickness of the surface layer and perform elemental analysis of the first layer 31 based on the detection result of the fluorescent X-ray, and measure the thickness t1 of the first layer 31. For example, when the first layer 31 is stacked on a plurality of layers, the X-ray analysis device 100 may measure the thickness t1 of the first layer 31 by calculation using the formula (5) or the formula (3) including terms related to layers other than the first layer 31 and the second layer 32. The X-ray analysis device 100 may measure the thickness t1 of the first layer 31 by calculation using the formula (3) or the formula (5), making the plurality of layers other than the first layer 31 equivalent to the second layer 32.

[0064] <Implementation Method 2> The functional configuration of the X-ray analyzer 100 and the analyzer 1 of the second embodiment is the same as that of the first embodiment. In the second embodiment, the X-ray analyzer 100 calculates the thickness t1 of the first layer 31 included in the sample 3 based on the fluorescent X-rays. When the thickness t1 of the first layer 31 is relatively small, the thickness t1 can be calculated based on the fluorescent X-rays without using the detection result of the transmission X-rays.

[0065] Figure 6 This is a flowchart showing an example of the steps of the processing performed by the X-ray analysis device 100 of the second embodiment for measuring the thickness t1 of the first layer 31 based on the fluorescent X-ray. The irradiation unit 21 irradiates the sample 3 with X-rays (S21), and the fluorescent X-ray detector 22 detects the fluorescent X-rays (S22). The fluorescent X-ray detector 22 outputs a signal of an intensity corresponding to the energy of the fluorescent X-rays to the first signal processing unit 24, and the first signal processing unit 24 counts the signal according to the signal value, and outputs data indicating the relationship between the signal value and the count value to the analysis unit 1. The analysis unit 1 obtains the detection result of the fluorescent X-ray by receiving the data from the first signal processing unit 24 and the second signal processing unit 25 (S23). The analysis unit 1 generates a spectrum of the fluorescent X-rays and stores the spectrum data in the storage unit 14.

[0066] The analysis unit 1 calculates the thickness t1 of the first layer 31 included in the sample 3 by performing elemental analysis based on the spectrum of fluorescent X-rays (S24). In S24, the operation unit 11 determines the elements included in the first layer 31 by performing elemental analysis based on the spectrum of fluorescent X-rays, as in the first embodiment. In addition, the operation unit 11 calculates the thickness t1 of the first layer 31 based on the fluorescent X-rays using the existing technology. For example, the operation unit 11 calculates the thickness t1 of the first layer 31 based on the intensity of the peak included in the obtained spectrum of fluorescent X-rays according to the relationship between the intensity of the peak caused by a specific element included in the spectrum of fluorescent X-rays and the thickness t1. The relationship between the intensity of the peak and the thickness t1 is previously investigated and stored in the storage unit 14.

[0067] The analysis unit 1 outputs the calculated thickness t1 of the first layer 31 (S25). In S25, the operation unit 11 causes the display unit 27 to display the calculated value of the thickness t1 of the first layer 31, thereby outputting the thickness t1. The operation unit 11 stores the thickness t1 of the first layer 31 in the storage unit 14. After S25 ends, the analysis unit 1 ends the process for measuring the thickness t1 of the first layer 31.

[0068] The X-ray analysis device 100 can execute both the processing of S101 to S110 and the processing of S21 to S24. The X-ray analysis device 100 can switch between the processing of S101 to S110 and the processing of S21 to S24 as the processing to be executed. For example, the user operates the operation unit 15 to input a switching instruction of the processing to the analysis unit 1, and the analysis unit 1 switches the processing to be executed according to the switching instruction.

[0069] When the thickness t1 of the first layer 31 is relatively small, the X-ray analyzer 100 can simply measure the thickness t1 of the first layer 31 by executing the processes of S21 to S25. When the thickness t1 of the first layer 31 is relatively large, the X-ray analyzer 100 can more accurately measure the thickness t1 of the first layer 31 by executing the processes of S101 to S110. In this way, in the second embodiment, the thickness t1 of the first layer 31 can be measured by an appropriate method according to the size of the thickness t1 of the first layer 31.

[0070] In Embodiments 1 and 2, the thickness t1 of the first layer 31 is measured using the mass absorption coefficient of X-rays. However, the X-ray analyzer 100 may measure the thickness t1 of the first layer 31 using a linear absorption coefficient as the absorption coefficient of X-rays.

[0071] In Embodiments 1 and 2, the fluorescent X-ray detector 22 and the transmission X-ray detector 23 are radiation detectors having radiation detection elements formed using semiconductors. The fluorescent X-ray detector 22 and the transmission X-ray detector 23 may also be radiation detectors having radiation detection elements other than radiation detection elements formed using semiconductors. The fluorescent X-ray detector 22 and the transmission X-ray detector 23 may also be detectors having multiple channels. For example, the fluorescent X-ray detector 22 and the transmission X-ray detector 23 may also be strip detectors, pixel array detectors, or linear sensors, or may be composed of a plurality of detectors arranged in an array. When a detector having multiple channels is used, a high count rate measurement can be performed compared to the case of using a detector having a single channel.

[0072] The fluorescence X-ray detector 22 and the transmission X-ray detector 23 are not limited to energy dispersive detectors, and any detector that can detect the intensity of X-rays of specific energies E1 and E2 may be used. For example, the fluorescence X-ray detector 22 and the transmission X-ray detector 23 may be formed using a CCD (Charge Coupled Device) optical sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) optical sensor, or may be formed using a combination of a photomultiplier tube and a scintillator. Such a detector may be combined with a filter that allows X-rays of specific energy to pass through, or an element that focuses X-rays of specific energy by diffracting them.

[0073] In the first and second embodiments, an example in which the horizontal axis of the X-ray spectrum is energy is shown, but the X-ray analysis device 100 may also be a method of processing a spectrum in which a value other than energy, such as wavelength or wave number, is used as the horizontal axis. In this method, the analysis unit 1 may also use two wavelengths or wave numbers corresponding to two energies to perform processing to calculate the thickness t1 of the first layer 31.

[0074] The X-ray analysis device 100 may also be provided with a mechanism capable of adjusting the intensity of the transmitted X-rays. When the intensity of the transmitted X-rays is too high, more X-rays are incident on the transmitted X-ray detector 23, the probability of superposition of signals corresponding to the incidence of the X-rays increases, the dead time of detection increases, or the transmitted X-ray detector 23 may fail. In order to be able to cope with various samples 3 of different thicknesses or to prevent failure of the transmitted X-ray detector 23, it is preferable to be able to adjust the intensity of the transmitted X-rays. For example, the X-ray analysis device 100 is provided with an adjustment mechanism that adjusts the intensity of the transmitted X-rays when the intensity of the detected transmitted X-rays exceeds a predetermined threshold or when the dead time exceeds a predetermined threshold. For example, the adjustment mechanism adjusts the intensity of the X-rays irradiated by the irradiation unit 21 by adjusting the current flowing through the X-ray tube. For example, the adjustment mechanism includes a collimator disposed between the irradiation unit 21 and the sample 3, and the intensity of the X-rays irradiated to the sample 3 is adjusted by changing the size of the collimator or replacing collimators of multiple sizes. For example, the adjustment mechanism adjusts the intensity of the transmission X-rays by adjusting the distance between the sample 3 and the transmission X-ray detector 23 .

[0075] The present invention is not limited to the contents of the above-mentioned embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

[0076] The matters described in each embodiment can be combined with each other. In addition, the independent claims and dependent claims described in the claims can be combined with each other in all combinations regardless of the reference form. In addition, the form of recording and citing two or more other claims (multiple claims form) is used in the claims, but it is not limited to this. It is also possible to record in the form of recording multiple claims (multiple citing multiple claims) that at least one multiple claim is cited. Description of reference numerals:

[0077] 100: X-ray analysis device; 1: analysis unit; 10: recording medium; 141: computer program; 21: irradiation unit; 22: fluorescent X-ray detector; 23: transmission X-ray detector; 3: sample; 31: first layer; 32: second layer.

Claims

1. A thickness measurement method, characterized in that: irradiating a sample including a first layer and a second layer stacked together with the X-ray so that the X-ray passes through the first layer and the second layer in that order, detecting fluorescent X-rays generated from the first layer, detecting the transmitted X-rays after passing through the sample, determining an absorption coefficient of X-rays in the first layer and a density of the first layer by elemental analysis based on the fluorescent X-rays, The thickness of the first layer is calculated based on the intensities of the transmitted X-ray at two different energies, the absorption coefficient, and the density.

2. The thickness measurement method according to claim 1, characterized in that: The difference between the two energies is within a specified range.

3. The thickness measurement method according to claim 2, characterized in that: The absorption edge of the element contained in the second layer is not contained in the energy range between the two energies.

4. The thickness measurement method according to any one of claims 1 to 3, characterized in that: The two energies are determined by elemental analysis based on the fluorescent X-rays so that the absorption edge of the element included in the first layer is included in an energy range between the two energies.

5. An X-ray analysis device, characterized in that: The X-ray analysis device comprises: an irradiation unit that irradiates a sample including a first layer and a second layer stacked together with X-rays in such a manner that the X-rays pass through the first layer and the second layer in that order; a fluorescent X-ray detector for detecting the fluorescent X-rays generated from the first layer; a transmission X-ray detector for detecting the transmission X-rays after passing through the sample; as well as Analytics Department, The analyzing unit determines the X-ray absorption coefficient in the first layer and the density of the first layer by elemental analysis based on the fluorescent X-rays, The analysis unit calculates the thickness of the first layer based on the intensities of the transmission X-rays at two different energies, the absorption coefficient, and the density.

6. The X-ray analysis device according to claim 5, characterized in that: The analysis unit calculates the thickness of the first layer by elemental analysis based on the fluorescent X-rays without using the detection result of the transmission X-rays.

7. An information processing device, characterized in that: The information processing device comprises: an acquisition unit that acquires a detection result of fluorescent X-rays generated from the first layer by irradiating a sample including a first layer and a second layer stacked together in such a manner that the X-rays pass through the first layer and the second layer in that order, and a detection result of transmission X-rays that pass through the sample; a determination unit that determines an absorption coefficient of X-rays in the first layer and a density of the first layer by element analysis based on a detection result of the fluorescent X-rays; as well as The calculation unit calculates the thickness of the first layer based on the intensities of the transmission X-rays at two different energies, the absorption coefficient, and the density.

8. A computer program, characterized in that The computer program causes the computer to execute the following processing: performing elemental analysis based on a detection result of fluorescent X-rays generated from the first layer by irradiating a sample including a first layer and a second layer stacked together in such a manner that the X-rays pass through the first layer and the second layer in that order, thereby determining an absorption coefficient of X-rays in the first layer and a density of the first layer, The thickness of the first layer is calculated based on the intensities of the transmission X-rays at two different energies included in the detection results of the transmission X-rays after passing through the sample, the absorption coefficient, and the density.

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