Analysis method, automatic analysis method, and automatic analysis device

Abstract

To enable precise analysis of an object.SOLUTION: An analysis method includes: a step of irradiating a sample with electrons by a predetermined irradiation method provided with each stage of a plurality of times of irradiation or continuous irradiation; a step of detecting intensity of any of an X-ray, an electron, or current flowing through the sample generated by irradiation in each stage; and a step of obtaining a predetermined spectrum from the detected intensity in each stage, where acceleration voltage of the irradiated electron is different or bias voltage on the sample side is different in each stage of the irradiation method.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an analysis method, an automatic analysis method, and an automatic analysis device. [Background technology]

[0002] Conventionally, there are methods for analyzing objects using X-rays and the like.

[0003] For example, there is a method using the XAFS (X-ray Absorption Fine Structure) method (see Non-Patent Document 1). The XAFS method has the following features: structural information on non-crystalline materials, information obtained by element selection, and non-destructive measurement. When non-destructive measurement is required, the XAFS method, which has the above features, is used as an effective analytical tool. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] SPring-8 Large Synchrotron Radiation Facility "XAFS - Methods and Examples" URL: http: / / www.spring8.or.jp / ja / science / meetings / 2016 / 2nd_cultural_ws / xafs / Summary of the Invention [Problem to be solved by the invention]

[0005] There are several issues with analytical methods that use X-rays. First, it is difficult to reduce the irradiation area with X-rays. This is because X-rays cannot be bent as easily as electrons, and complex use of crystal mirrors and other elements is required. Second, the use of a synchrotron radiation facility is a prerequisite. This is because synchrotron radiation, which is a continuous beam of light, must be used in order to continuously change the energy of the X-rays.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide an analysis method, an automatic analysis method, and an automatic analysis device that enable precise analysis of an object. [Means for solving the problem]

[0007] The analytical method disclosed herein comprises the steps of irradiating a sample with electrons using a predetermined irradiation method with multiple or continuous irradiation stages, detecting the intensity of any of X-rays, electrons, or current flowing through the sample generated by the irradiation at each stage, and obtaining a spectrum from the detected intensities at each stage, wherein the acceleration voltage of the irradiating electrons is different or the bias voltage on the sample side is different at each stage of the irradiation method.

[0008] The automatic analysis method disclosed herein is a method implemented on a computer, and includes the steps of irradiating a sample with electrons using a predetermined irradiation method that includes multiple or continuous irradiation stages, and detecting the intensity of any of X-rays, electrons, or current flowing through the sample generated by the irradiation at each stage, obtaining a spectrum from the detected intensity at each stage, and acquiring sample information from the spectrum, wherein the acceleration voltage of the irradiating electrons is different or the bias voltage on the sample side is different at each stage of the irradiation method.

[0009] The automatic analysis device of the present disclosure includes an irradiator that irradiates a sample with electrons, a detector that detects the intensity of either X-rays, electrons, or a current flowing through the sample generated by the irradiation, an automatic control unit that controls the irradiator to irradiate the sample with electrons using a predetermined irradiation method that includes multiple or continuous irradiation stages, and controls the detector to detect the intensity at each stage, a generation unit that generates a spectrum from the intensity at each stage detected by the detector, an analysis unit that analyzes the sample from the generated spectrum, and an output control unit that displays or saves the analysis results obtained by the analysis unit, and in which the acceleration voltage of the irradiated electrons is different at each stage of the irradiation method, or the bias voltage on the sample side is different. [Effects of the Invention]

[0010] The analysis method, automatic analysis method, and automatic analysis device of the present disclosure enable precise analysis of an object. [Brief explanation of the drawings]

[0011] [Figure 1] Figure 1 shows an image of the combined EDS-SEM. [Figure 2] FIG. 2 is a block diagram showing the configuration of the automatic analysis system of this embodiment. [Figure 3] FIG. 3 is a block diagram showing the hardware configuration of the analyzer as a computer in the automatic analysis system. [Figure 4] FIG. 4 is a flowchart showing the flow of the automatic analysis process. [Figure 5] FIG. 5 is a diagram showing an example of an EDS spectrum. [Figure 6] FIG. 6 is a diagram showing an example of an electronic absorption spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0013] In this embodiment, we propose a technology that combines an apparatus that irradiates a sample with electrons, such as a scanning electron microscope (SEM), with an apparatus that detects X-rays, such as an energy dispersive X-ray analyzer (EDS). The following describes an example in which an SEM apparatus equipped with an EDS (EDS-SEM) is used. Figure 1 shows an image of the combined EDS-SEM. In this embodiment, the acceleration voltage of the electron beam incident on the sample is changed to sweep the electron energy, while detecting X-rays emitted from the sample 114, and a spectrum (electron absorption spectrum) is obtained using the detected X-rays as its intensity. In the following, the SEM corresponds to the electron irradiator 110, and the EDS corresponds to the detector 112.

[0014] Fig. 2 is a block diagram showing the configuration of the automatic analysis system of this embodiment. As shown in Fig. 2, the automatic analysis system 100 is composed of an electron irradiator 110, a detector 112, a sample 114 to be analyzed, a bias voltage application unit 116, and an analysis device 120. Note that the reference numeral for the sample 114 will be omitted in the following description.

[0015] The analysis device 120 includes an automatic control unit 122, a generation unit 124, an analysis unit 126, and an output control unit 128. The electron irradiator 110, the detector 112, and the analysis device 120 can constitute an automatic analysis device of the present disclosure.

[0016] Fig. 3 is a block diagram showing the hardware configuration of the analysis device 120 as a computer in the automated analysis system 100. As shown in Fig. 3, the analysis device 120 has a CPU (Central Processing Unit) 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a storage 14, an input unit 15, a display interface (I / F) 16, and a communication interface (I / F) 17. Each component is connected to each other via a bus 19 so that they can communicate with each other.

[0017] The CPU 11 is a central processing unit that executes various programs and controls each part. That is, the CPU 11 reads a program from the ROM 12 or the storage 14 and executes the program using the RAM 13 as a work area. The CPU 11 controls each of the above components and performs various arithmetic processing in accordance with the program stored in the ROM 12 or the storage 14. In this embodiment, the ROM 12 or the storage 14 stores an image analysis program.

[0018] The ROM 12 stores various programs and various data. The RAM 13 temporarily stores programs or data as a working area. The storage 14 is configured with a storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive) and stores various programs including the operating system and various data.

[0019] The input unit 15 includes a pointing device such as a mouse and a keyboard, and is used to perform various inputs.

[0020] The display interface 16 is, for example, a liquid crystal display, and displays various information. The display interface 16 may function as the input unit 15 by adopting a touch panel system.

[0021] The communication interface 17 is an interface for communicating with other devices such as terminals, and uses standards such as Ethernet (registered trademark), FDDI, and Wi-Fi (registered trademark).

[0022] Next, we will explain each functional configuration of the automatic analysis system 100. Each functional configuration of the analysis device 120 is realized by the CPU 11 reading out an image analysis program stored in the ROM 12 or storage 14, expanding it in the RAM 13, and executing it.

[0023] The electron irradiator 110 irradiates the sample with electrons. Note that the electrons to be irradiated are not limited to an electron beam.

[0024] The detector 112 detects the intensity of X-rays generated by irradiation. Note that detection is not limited to X-rays, and the intensity of electrons generated by irradiation or current in the sample may also be detected. Furthermore, the detection of X-ray intensity is not limited to the area or height of the spectrum, and is not particularly limited as long as it is correlated with the energy of the electrons.

[0025] Here, we will explain how the intensity of detected X-rays and other rays changes. Changing the energy when electrons collide with a sample also changes the intensity (spectrum) of the detected X-rays. The energy value at which intensity begins to appear (the lowest energy value at which the spectrum begins to rise) is a value specific to the type of element and its chemical state. Therefore, by detecting X-rays while changing the energy when electrons collide, it is possible to know the energy value at which the spectrum begins to rise, and from this value it is possible to identify the element and its chemical state. The energy can be changed in the following ways, and so the automatic control unit controls the energy change: (1) changing the electron acceleration voltage (changing the energy of the colliding electrons), (2) changing the voltage of the electric field on the sample side (changing the energy of the electrons at the time of collision).

[0026] Next, each component of the analysis device 120 will be described. The automatic control unit 122 controls the electron irradiator 110 and the detector 112. The automatic control unit 122 causes the irradiator to irradiate electrons onto the sample using a predetermined irradiation method that includes multiple or continuous irradiation stages. The automatic control unit 122 controls the detector 112 to detect the intensity at each irradiation stage. Here, at each stage of the irradiation method, the acceleration voltage of the electrons irradiated from the electron irradiator 110 is controlled to vary due to changes in intensity. Note that, in addition to the electron acceleration voltage, the application unit 116 may also be controlled to vary the bias voltage on the sample side due to changes in intensity. The polarity of the bias voltage applied to the sample may be either positive or negative. The generation unit 124 generates multiple EDS spectra according to the manner in which the voltage is changed.

[0027] The generation unit 124 generates an EDS spectrum from the intensity of each stage detected by the detector 112. Here, when the electron acceleration voltage is controlled to be different, multiple EDS spectra with different acceleration voltages of the irradiated electrons are generated as the EDS spectrum. Furthermore, when the bias voltage on the sample side is controlled to be different, multiple spectra with different bias voltages on the sample side are generated as the EDS spectrum. Note that instead of an EDS spectrum, a spectrum of electrons or sample current may be generated. Examples of the generated EDS spectrum, analysis, and display will be described in the experimental examples below. The EDS spectrum, electron, or sample current spectrum are examples of the "predetermined spectrum" in this disclosure.

[0028] The analysis unit 126 analyzes the sample from the generated spectrum. For example, analysis can be performed by plotting the intensity of multiple EDS spectra against the energy of the incident electron beam. Sample information can be obtained through analysis. Here, the rising energy shown in multiple spectra, i.e., the absorption edge, can be analyzed. Since the rising edge has characteristics depending on the type of object, this allows for precise object identification. Alternatively, the intensity of each detected step can be mapped without using a spectrum.

[0029] The output control unit 128 displays (or stores) the analysis results obtained by the analysis unit 126. The output control unit 128 can display spectrum graphs, analyzed numerical values, and the like as the analysis results.

[0030] Next, the operation of the automatic analysis system 100 according to this embodiment will be described. Fig. 4 is a flowchart showing the flow of the automatic analysis process. The CPU 11 reads out an automatic analysis program from the ROM 12 or storage 14, loads it into the RAM 13, and executes it, thereby performing the automatic analysis process as an automatic analysis method.

[0031] In step S100, the CPU 11, as the automatic control unit 122, causes the electron irradiator 110 to irradiate electrons onto the sample using a predetermined irradiation method that includes multiple or continuous irradiation stages. In addition, the CPU 11 causes the application unit 116 to apply a voltage to the sample at any timing in accordance with the irradiation.

[0032] In step S102, the CPU 11 functions as the automatic control unit 122 and controls the detector 112 to detect the intensity at each stage of irradiation.

[0033] In step S104, the CPU 11 functions as the generation unit 124 to generate a spectrum from the detected intensities at each stage.

[0034] In step S106, the CPU 11 functions as the analysis unit 126 and analyzes the sample from the generated spectrum.

[0035] In step S108, the CPU 11 functions as the output control unit 128 to display (or store) the obtained analysis results.

[0036] As described above, the automatic analysis system according to this embodiment enables precise analysis of an object.

[0037] [Experimental Example] An experimental example of this embodiment will be described. The samples used in the experiment were (1) Si (a substrate with the native oxide film removed from the surface) and (2) SiO2 (a thermally oxidized film formed on a Si substrate). Figure 5 shows an example of an EDS spectrum. The spectrum in Figure 5 is the EDS spectrum of Si when the accelerating voltage (energy) of the incident electron beam is changed. Figure 6 shows an example of an electronic absorption spectrum. The intensity information of these EDS spectra, such as the peak area, is plotted against the energy of the incident electron beam to obtain the electronic absorption spectrum. The rising energy (absorption edge) differs between Si and SiO2, starting from 1.84 keV and 1.85 keV. The graph of the electronic absorption spectrum, the rising energy, and other information can be obtained as sample analysis information by the analysis unit 126. This result is consistent with the results obtained by X-ray absorption spectroscopy, a conventional technique described in Reference 1. Thus, the present method has experimentally confirmed that it is possible to identify chemical states. [Reference 1] N. Isomura et al., Appl. Surf. Sci. 355 (2015) 268

[0038] The application of the automated analysis method of this embodiment enables the following precise analyses: (1) Elements can be identified because the energy value of the absorption edge (intensity rise) in the absorption spectrum is element-specific. (2) Chemical states can be identified because the energy value and spectral shape of the absorption edge (intensity rise) in the absorption spectrum differ depending on the chemical state. (3) Micro-area measurements are possible because electrons can be used in electron microscopes to reduce the irradiation area using electron lenses, etc. (4) Information on the sample surface can be obtained because electron beams do not penetrate deeply into the sample. (5) Measurement of the same locations as scanning electron microscopes is possible. (6) Unlike X-ray absorption spectroscopy, this can be achieved inexpensively using laboratory equipment because the basic equipment configuration is no different from that of a scanning electron microscope equipped with an X-ray detector. (7) Chemical state inspection equipment can also be realized because the minimum equipment configuration is an electron gun and an X-ray detector.

[0039] The present disclosure is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the spirit and scope of the present invention. For example, the generation unit 124 may generate a differential spectrum of a minute signal using a lock-in amplifier.

[0040] The automatic analysis process executed by the CPU after reading the software (program) in the above embodiment may be executed by various processors other than the CPU. Examples of such processors include programmable logic devices (PLDs) (such as field-programmable gate arrays (FPGAs)) whose circuit configuration can be changed after fabrication, application-specific integrated circuits (ASICs), graphics processing units (GPUs), and other dedicated electrical circuits that are processors with circuit configurations specifically designed to execute specific processes. The automatic analysis process may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs, or a combination of a CPU and an FPGA). The hardware structure of these various processors is, more specifically, an electrical circuit that combines circuit elements such as semiconductor devices.

[0041] In the above embodiment, the automatic analysis processing program is pre-stored (installed) in a ROM or storage device, but the present invention is not limited to this. The program may be provided in a form recorded on a non-transitory recording medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The program may also be downloaded from an external device via a network. [Explanation of symbols]

[0042] 100 Automatic Analysis System 110 Electron irradiator 112 detector 114 samples 116 Applicator 120 Analyzer 122 Automatic control unit 124 Generation part 126 Analysis Department 128 Output control section

Claims

1. irradiating the sample with electrons using a predetermined irradiation regime with multiple or successive irradiation stages; At each stage, detecting the intensity of either X-rays, electrons, or current flowing through the sample generated by the irradiation; and obtaining a predetermined spectrum from the detected intensities of each step; In each stage of the irradiation method, the acceleration voltage of the irradiated electrons is different, or the bias voltage on the sample side is different, The step of obtaining the spectrum includes obtaining a plurality of the spectra at each stage, An analytical method, wherein the step of acquiring information about the sample comprises analyzing an electronic absorption spectrum obtained with respect to the energy of the incident electron beam using information about the intensity of each of the spectra.

2. 1. A computer-implemented method comprising: a step of irradiating a sample with electrons by a predetermined irradiation method including multiple or continuous irradiation steps, and detecting the intensity of any of X-rays, electrons, or current flowing through the sample generated by the irradiation at each step; obtaining a predetermined spectrum from the detected intensities of each stage; and acquiring information about the sample from the spectrum; In each stage of the irradiation method, the acceleration voltage of the irradiated electrons is different, or the bias voltage on the sample side is different, The step of obtaining the spectrum includes obtaining a plurality of the spectra at each stage, An automated analysis method, wherein the step of acquiring information about the sample comprises analyzing an electronic absorption spectrum obtained for each energy of the incident electron beam using information about the intensity of each of the spectra.

3. an irradiator for irradiating the sample with electrons; a detector that detects the intensity of any of X-rays, electrons, or current flowing through the sample generated by the irradiation; an automatic control unit that controls the irradiator to irradiate electrons onto the sample using a predetermined irradiation method that includes multiple or continuous irradiation steps, and controls the detector to detect the intensity at each step; a generation unit that generates a predetermined spectrum from the intensity of each stage detected by the detector; an analysis unit that analyzes the sample from the generated spectrum; an output control unit that displays the analysis results obtained by the analysis unit, In each stage of the irradiation method, the acceleration voltage of the irradiated electrons is different, or the bias voltage on the sample side is different, the generation unit generates a plurality of spectra at each stage as the spectrum, The analysis unit analyzes the electronic absorption spectrum obtained for each energy of the incident electron beam using information on the intensity of each of the spectra.

4. the automatic control unit controls a voltage of electrons from the irradiator or a voltage from an application unit to change the intensity, When controlling the irradiator due to the change in intensity, the irradiator is controlled so that an acceleration voltage of electrons irradiated from the irradiator is different, and the generation unit generates a plurality of spectra having different acceleration voltages of the irradiated electrons as the spectrum, When the application unit is controlled to change the intensity, the bias voltage Vcc is applied from the application unit to the sample side.

4. The automatic analyzer according to claim 3, wherein the bias voltage is controlled to be different, and the generation unit generates a plurality of spectra with different bias voltages on the sample side as the spectrum.

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