RADIATION ANALYSIS SYSTEM, SYSTEM WORKING WITH A BEAM OF CHARGED PARTICLES AND RADIATION ANALYSIS METHOD

Abstract

Radiation analysis system, comprising: a superconducting transition edge sensor (201) that detects radiation, a current sensing mechanism (206) that detects a current flowing through the superconducting transition edge sensor (201), and a computer subsystem (250) that processes a current detection signal from the current detection mechanism (206), the computer subsystem (250) performs the following: a process for calculating a baseline current of the current detection signal, a process for calculating a peak value of a signal pulse generated in the detection signal when the superconducting transition edge sensor (201) detects the radiation, a process for acquiring correlation data based on the baseline current and the peak value when radiation with multiple energies is detected under two or more different temperature conditions by the superconducting transition edge sensor (201), and a process for correcting the peak value of the signal pulse or an energy value calculated from the peak value based on the baseline current before the signal pulse is generated when radiation of unknown energy is detected by the superconducting transition edge sensor (201) and the correlation data.

Description

Technical field

[0001] The present invention relates to a radiation analysis system, a system operating with a beam of charged particles and a radiation analysis method. Technical background

[0002] Radiation analyzers capable of distinguishing radiation energy include energy-dispersive X-ray detectors (hereinafter referred to as "EDS") and wavelength-dispersive X-ray detectors (hereinafter referred to as "WDS"). The EDS converts the energy of an X-ray beam entering the detector into an electrical signal and calculates the energy based on the magnitude of this electrical signal. The WDS monochromatizes the X-ray beam using a spectrometer and detects the monochromatic X-ray beam using a proportional counter or similar device.

[0003] Semiconductor detectors such as silicon-lithium detectors, silicon drift detectors, and germanium detectors are widely used as energy detectors (EDS). For example, silicon-lithium or silicon drift detectors are used for elemental analysis in electron microscopes, enabling energy detection in the range of approximately 0.1 keV to 20 keV. However, because their operation depends on the band gap of the silicon used in the detector (around 1.1 eV), it is difficult to improve the energy resolution to about 120 eV or below, which is more than ten times worse than that of a wide-field detector (WDS).

[0004] If the energy resolution, which is one of the indices indicating the performance of the X-ray detector, is, for example, 120 eV, this means that the energy can be detected with an uncertainty of 120 eV when the X-ray detector is irradiated with X-rays. The smaller the uncertainty, the higher the energy resolution. If X-rays are detected that consist of two adjacent spectra with a difference of approximately 20 eV, two peaks can be separated as long as the energy resolution is approximately 20 eV to 30 eV.

[0005] As an alternative to the semiconductor detector used for EDS, an energy-dispersive superconducting X-ray analyzer, which also has an energy resolution equivalent to that of WDS, has attracted attention. Among superconducting X-ray analyzers, one detector incorporating a superconducting transition edge sensor (transition edge sensor, hereinafter referred to as "TES") is a highly sensitive calorimeter that utilizes a sudden change in resistance between the superconductivity and the normal conductivity of a thin metal film (for example, a change in resistance due to a temperature change of a few mK is 100 mΩ). The TES is also known as a microcalorimeter.

[0006] The TES analyzes a sample by detecting its temperature change, which occurs when a fluorescent X-ray beam or a characteristic X-ray beam generated by irradiation with a primary X-ray beam or a primary electron beam enters the TES. The TES has a higher energy resolution than the semiconductor detector, for example, an energy resolution of 10 eV or below for a 5.9 keV X-ray beam.

[0007] Although it is important to keep the baseline current flowing through the TES constant in order to achieve the high energy resolution of the TES, it is technically difficult to make the change in the baseline current zero, which is why various sensitivity correction methods have been proposed.

[0008] For example, patent literature 1 discloses an X-ray analyzer with “a sensitivity correction operating unit 7 which corrects a current detected by a current detection mechanism 4 or a peak value measured by a pulse height analyzer 5 depending on a change width for a case in which the change in the baseline current exceeds a setpoint” (see abstract in patent literature 1).

[0009] Patent literature 2 discloses a radiation analyzer with "a sensitivity correction operating unit 7 which corrects the sensitivity of a TES 1 on the basis of the ratio between a pre-seen output from a first heater 20 and a peak value measured by a pulse height analyzer 5" (see summary in patent literature 2). List of citations from patent literature Patent literature 1: JP 2009 - 271 016 A Patent literature 2: JP 2014 - 38 074 A

[0010] A radiation analyzer in which the temperature is controlled by means of peak and correction values ​​of the signal pulses based on a known radiation energy is disclosed in DE 10 2013 108 819 A1. Summary of the invention: Technical problem

[0011] However, in the X-ray analyzer according to patent literature 1, the baseline current must be constantly monitored and additional correction data must be recorded each time the baseline current flowing through the TES changes.

[0012] The radiation analyzer according to patent literature 2 pre-captures correlation characteristics between the heater output and the TES sensitivity and then corrects the peak value of the TES signal pulse using the TES sensitivity corresponding to the heater output when the TES signal pulse is captured in an actual measurement. However, because the heater output has a slow response time, high energy resolution cannot be achieved when the baseline current changes rapidly.

[0013] Therefore, the present disclosure provides a radiation analysis system that does not need to acquire additional correction data and that can maintain a stably high energy resolution. Solution to the problem

[0014] The radiation analysis systems and radiation analysis methods of the present invention are defined in the independent claims. Further advantageous embodiments are specified in the dependent claims.

[0015] Further features relating to the present disclosure will become clear from the description in this patent specification and the accompanying drawings. Moreover, aspects of the present disclosure are achieved and realized through elements and combinations of various elements, as well as the following detailed descriptions and modes of the accompanying claims.

[0016] The description of the patent specification merely presents typical examples and does not in any way restrict the claims or application examples of the present disclosure. Advantageous effects of the invention

[0017] The radiation analysis system according to the present disclosure can obtain a stably high energy resolution without the need to acquire additional correction data.

[0018] Other problems, configurations and effects will become clear from the following description of embodiments. Brief description of the drawings

[0019] They show: Fig. 1 a configuration of a scanning electron microscope system according to a first embodiment, Fig. 2 a schematic diagram of a configuration of a radiation analyzer, Fig. 3 a schematic diagram of a TES configuration, Fig. 4 a schematic diagram of a configuration of part of the radiation analyzer, Fig. 5 a flowchart of a measurement preparation procedure performed by the radiation analyzer, Fig. 6. A graph of the change in baseline current from the beginning to the end of the measurement preparation. Fig. 7 a schematic diagram of a correlation data acquisition screen display for measurement preparation, Fig. 8 a flowchart of a procedure for correcting a peak value by a correction unit, Fig. 9 a graph of a change in a current detected by the correction unit, Fig. 10 Correlation data between the baseline current and the peak value of the radiation analyzer, Fig. 11 the correlation data, when the energy of radiation entering the TES of the radiation analyzer is proportional to the peak value, Fig. 12 the correlation data when the energy of the radiation entering the TES of the radiation analyzer is not proportional to the peak value, and Fig. 13 a correlation data acquisition screen display for acquiring correlation data according to a second embodiment. Description of embodiments

[0020] The following describes embodiments of the present disclosure with reference to the drawings.

[0021] Although an example of the use of a scanning electron microscope as an electron microscope (subsystem in which a beam of charged particles is used) in a system operating with a beam of charged particles according to the embodiments is described, this is merely one example of a technology disclosed herein, and the technology of the present disclosure is not limited to the embodiments described below. In the present disclosure, the electron microscope is intended to encompass a wide variety of devices that acquire an image of a sample using an electron beam. For example, the technology according to the present disclosure can also be applied to a scanning electron microscope, a transmission electron microscope, and a sample processing device or sample analyzer equipped with a scanning electron microscope.

[0022] Furthermore, examples of an X-ray analyzer using the electron beam include an inspection device, an examination device, a sample measurement device, and the like, employing a scanning electron microscope. The X-ray analyzer using the electron microscope should include a system in which respective devices incorporating the electron microscope described above are interconnected via a network, and a device combining the respective devices described above.

[0023] Here, a "sample" encompasses a wide variety of objects to be observed and analyzed. For example, a "sample" might include a semiconductor wafer made of silicon or similar materials, a high-performance material such as those used in lithium batteries, a biological sample, and the like. First embodiment<Konfiguration des Rasterelektronenmikroskopsystems>

[0024] Fig. Figure 1 shows a configuration of a scanning electron microscope system 100 (a system operating with a beam of charged particles) according to a first embodiment. As in Fig. As shown in Figure 1, the scanning electron microscope system 100 includes a radiation analysis subsystem 200 (radiation analysis system), a scanning electron microscope 300 (subsystem for irradiation with a beam of charged particles), a high voltage supply 400 and a computer subsystem 500.

[0025] The scanning electron microscope 300 includes an electron source 301, a converging lens 303, a deflection coil 304, an objective lens 305, a sample stage 307, a backscattered electron detector 308 and a secondary electron detector 309.

[0026] The computer subsystem 500 controls the operations of the scanning electron microscope 300 and the high-voltage power supply 400 and includes a total control unit 501, a control unit 502 for the electron-optical system, a table control unit 503, an A / D conversion unit 504, an image operating unit 505, a storage device 506, a display unit 507 and an input device 508.

[0027] A sample 306 to be examined is placed on the sample stage 307. The sample stage 307 moves in the XY direction based on a command signal from the stage control unit 503. The high-voltage supply 400 is connected to the electron source 301, and a voltage is applied from the high-voltage supply 400 to the electron source 301 based on the command signal from the overall control unit 501.

[0028] An electron beam 302 (beam of charged particles) emitted from the electron source 301 is collected by the converging lens 303 and the objective lens 305 on the basis of the command signal from the control unit 502 for the electron-optical system, and it is scanned by the deflection coil 304 over the sample 306.

[0029] The electron beam 302, striking sample 306, generates backscattered electrons and secondary electrons. The backscattered electrons reaching the backscattered electron detector 308 and the secondary electrons reaching the secondary electron detector 309 are converted into a current, output to the A / D conversion unit 504, and converted into a digital signal. The image processing unit 505 generates a SEM image and performs image processing using the digital signal generated by the A / D conversion unit 504.

[0030] The storage device 506, the display unit 507 and the input device 508 are connected to the overall control unit 501, and the SEM image generated by the image operating unit 505 is stored in the storage device 506 and displayed on the display unit 507 via the overall control unit 501.

[0031] The display unit 507 also shows a GUI screen to a user of the scanning electron microscope system 100 for entering a command. The user sends the command to the master control unit 501 by pressing the input device 508 via the GUI screen displayed on the display unit 507. The master control unit 501 controls each unit by changing an imaging condition or imaging position of the SEM image, changing a acquisition condition of the radiation analysis subsystem 200, and the like, by sending a command to the high-voltage power supply 400, to the control unit 502 for the electron-optical system, to the stage control unit 503, to the image operating unit 505, or to the radiation analysis subsystem 200 based on the user input.

[0032] The radiation analysis subsystem 200 is a device that can be used as a composition analyzer, for example, an electron microscope, an ion microscope, an X-ray microscope, a fluorescence X-ray microscope, and the like. The radiation analysis subsystem 200 detects a characteristic X-ray beam (radiation) emitted by the sample when irradiated with the electron beam 302 and calculates its energy. Because the characteristic X-ray beam has an element-specific energy, the radiation analysis subsystem 200 can analyze which element is located at the position on the sample 306 irradiated by the electron beam 302 by generating a spectrum in which the horizontal axis indicates the energy and the vertical axis indicates a count of X-rays.

[0033] The radiation analysis subsystem 200 is designed to send and receive (transmit) data and the command signal to and from the overall control unit 501 in the computer subsystem 500. The result of the element analysis performed by the radiation analysis subsystem 200 is output via the overall control unit 501 to the storage device 506 and the display unit 507. The overall control unit 501 can also transmit information about the detected element over the network to a data management server (not shown).

[0034] Fig. Figure 2 is a schematic diagram of a configuration of the radiation analysis subsystem 200. As in Fig. As shown in Figure 2, the radiation analysis subsystem 200 includes a TES 201, a sensor circuit unit 202, a bias current source 203, a current sensing mechanism 206, a first thermometer 209, a heater 210, a cooler 211 and a computer subsystem 250.

[0035] After receiving radiation, the TES 201 detects its energy as a temperature change and outputs this temperature change as a current signal. The detailed configuration of the TES 201 is described later. The bias current source 203 applies a current to the sensor circuit unit 202 to artificially drive the sensor circuit unit 202 at a constant voltage. The sensor circuit unit 202 is connected to the TES 201 and has a shunt resistor 204 and an input coil 205.

[0036] The shunt resistor 204 is connected in parallel to the TES 201 and has a resistance value lower than that of the TES 201. The input coil 205 is connected in series with the TES 201. When a bias current is applied to the sensor circuit unit 202 from the bias current source 203, the current is divided according to the resistance ratio between the resistance value of the shunt resistor 204 and the resistance value of the TES 201. That is, the voltage value of the TES 201 is determined by the voltage value determined by the current flowing through the shunt resistor 204 and the resistance value of the shunt resistor 204.

[0037] The current sensing mechanism 206 comprises a SQUID amplifier 207 (SQUID: Superconducting Quantum Interference Device) and a room-temperature amplifier 208. The SQUID amplifier 207 detects the magnetic field generated by the input coil 205, generates an electrical signal, and outputs this signal to the room-temperature amplifier 208. The room-temperature amplifier 208 detects a signal pulse of the current flowing through the TES 201 by amplifying and shaping the electrical signal output by the SQUID amplifier 207. In this way, the current sensing mechanism 206 can detect even very small changes in the current flowing through the TES 201 using the SQUID amplifier 207.It is mentioned later that, although the SQUID amplifier 207 using the input coil 205 and the room temperature amplifier 208 are used as the current sensing mechanism 206, other configurations can also be used as long as the change in the current flowing through the TES 201 can be detected.

[0038] In Fig. Figure 2 schematically represents the cooler 211 by an area surrounded by a dashed line, and it is shown that the TES 201, the sensor circuit unit 202, the SQUID amplifier 207, the first thermometer 209, and the heater 210 are installed inside the cooler 211. Furthermore, a cooling head (in Fig. 2 (not shown) are installed inside the cooler 211 and the first thermometer 209 and the heater 210 are installed in the cooling head.

[0039] The computer subsystem 250 comprises a pulse height analyzer 251, a correction unit 252, a spectrum generator 253, and a temperature control unit 254. Although not shown in the figures, the computer subsystem 250 also includes a display unit, a processor (operating circuit) in the form of a central processing unit (CPU), and a storage device for storing programs and the like. The functions of the respective modules of the computer subsystem 250 (pulse height analyzer 251, correction unit 252, spectrum generator 253, and temperature control unit 254) can be implemented, for example, by program processing by the processor. It should be noted that each module of the computer subsystem 250 can be incorporated into the overall control unit 501 described above or into another personal computer.

[0040] The pulse height analyzer 251 receives an input of a current detection signal from the current detected by the current detection mechanism 206 and calculates the peak value of the signal pulse of the current flowing through the TES 201. It should be noted that the "peak value" here includes a wide variety of signal pulses calculated to improve the accuracy of the analysis. For example, the "peak value" includes a height component of the signal pulse, an integrated value of the signal pulse, the signal pulse convolved with a filter such as a bandpass filter, and the like.

[0041] The correction unit 252 corrects the peak value calculated by the pulse height analyzer 251. Details of the peak value correction by the correction unit 252 according to the present embodiment are described later. In addition, the correction unit 252 receives an input of a detection signal of the current detected by the current detection mechanism 206 and calculates an average value of the baseline current.

[0042] The spectrum generation unit 253 generates an energy spectrum of the radiation detected by the TES 201 using the peak value corrected by the correction unit 252. The spectrum generation unit 253 generates the spectrum by repeating an operation to increment the peak value count by one in a histogram where the horizontal axis represents the peak value and the vertical axis represents the count value. Furthermore, if peak-to-energy conversion data is pre-acquired into the pulse height analyzer 251, the correction unit 252, or the spectrum generation unit 253, a histogram where the horizontal axis represents the energy and the vertical axis represents the count value can be displayed on the display unit.

[0043] The temperature control unit 254 controls the output of the heater 210.

[0044] Fig. Figure 3 is a schematic diagram of a TES 201 configuration. As shown in Fig. As shown in Figure 3, the TES 201 comprises an absorber 212, a second thermometer 213, and a membrane 214. The absorber 212 is a metal, a semimetal, a semiconductor, or the like for absorbing radiation such as X-rays, for example, made of gold, copper, or bismuth. The second thermometer 213 consists of the semiconductor and detects heat generated in the absorber 212 as a temperature change. The second thermometer 213 consists of a stack of two layers, for example, made of titanium and gold. The membrane 214 is made, for example, of silicon nitride. The membrane 214 loosely connects the second thermometer 213 to the cooling head 215 and controls the heat flow to the cooling head 215.

[0045] Fig. Figure 4 is a schematic diagram of a configuration of part of the radiation analysis subsystem 200. As in Fig. As shown in figure 4, the TES 201 and the shunt resistor 204 (in Fig. (4 not shown) and the SQUID amplifier 207 is provided at one tip of the heatsink 215. A substrate containing the TES 201 and a substrate containing the SQUID amplifier 207 are connected by superconducting wiring 216. The heatsink 215 is surrounded by a heat shield 217.

[0046] Within the cooling head 215 are provided the first thermometer 209, which monitors the temperature of the cooling head 215, and the heater 210. A resistance thermometer can be used as the first thermometer 209, and the sensor material can be, for example, a semiconductor such as germanium, a superconductor, or a metal oxide such as ruthenium oxide. The first thermometer 209 has a resistance value that depends on the temperature of the cooling head 215. Accurate temperature information of the cooling head 215 can be obtained by correlating the temperature and the electrical signal output by the first thermometer 209 and pre-storing this information in the temperature control unit 254.

[0047] The cooling head 215 is cooled by the cooler 211 to a temperature of 50 mK to 400 mK. Specifically, the TES 201 must be cooled to a temperature lower than the temperature at which the superconducting transition occurs. Examples of devices for cooling the cooler 211 include a dilution cooler and an insulated demagnetized cooler (adiabatic demagnetization refrigerator, hereinafter referred to as "ADR"). The former uses a cooling technology based on an enthalpy change that occurs when 3He melts from a dense phase in a mixing chamber into a dilute phase. The latter uses a technology for cooling an object connected to a magnetic body based on an entropy change that occurs when the magnetic body is aligned along a spin direction by applying a magnetic field and then the magnetic field is removed.In both cases, the cooling head 215 is installed in the position with the highest cooling.

[0048] If the temperature of the cooling head 215 is stabilized with the dilution cooler, the temperature control unit 254, once a target temperature has been set for it, controls the output of the heater 210 based on the temperature of the first thermometer 209. It should be noted that, in the ADR system, the temperature of the cooling head 215 is kept constant by controlling the strength of the magnetic field applied to the magnetic body based on the temperature of the first thermometer 209. <Arbeitsprinzip des TES>

[0049] The TES 201 uses a superconducting junction in the superconductor and maintains the operating point in an intermediate state between normal conductivity and superconductivity during radiation detection. When a single radiation wave is absorbed by the TES 201, this allows, for example, the detection of a change in resistance of a few mΩ for a temperature change of 100 µK and the detection of a signal pulse on the order of µA, while maintaining the operating point during the superconducting junction. Furthermore, if radiation of unknown energy enters the TES 201, the energy of the incident radiation can be determined from the peak value of the signal pulse by first calculating a relationship between the energy of the radiation and the peak value of the signal pulse.

[0050] When the TES 201 is held at its operating point during the superconducting transition, the operating point of the TES 201 is determined by the thermal equilibrium between the current flowing through the TES 201 (hereinafter referred to as the "TES current It") and a thermal connection to the heat sink 215. The energy resolution of the TES 201 is correlated with temperature, and the temperature is preferably kept as low as possible. The temperature of the heat sink 215 is, for example, maintained at approximately 50 mK to 400 mK. The TES current It is determined by the following formula (1): [Formula 1] It2Rt(T)=G(T−Tb)

[0051] In formula (1), the TES current It is described by the dynamic resistance Rt of the TES 201, the thermal conductivity G of the thermal connection between the second thermometer 213 and the cooling head 215 provided in the TES 201, the temperature T of the second thermometer 213, and the temperature Tb of the cooling head 215. Here, the baseline current represents the TES current It in a state where the TES 201 is not irradiated.

[0052] Furthermore, the relationship between the TES current It and the signal pulse ΔI is given by the following formula (2). Ideally, if the TES current It is constant, the signal pulse ΔI is always constant. [Formula 2] It=CTαEΔI

[0053] In equation (2), the TES current It and the signal pulse ΔI are described by the sensitivity α of the TES 201, the heat capacity C, the energy E of the incident radiation, and the temperature T of the second thermometer 213. As can be seen from equation (2), if the baseline current flowing through the TES 201 changes, the signal pulse ΔI changes, even if the TES 201 is irradiated with radiation of the same energy. Moreover, as can be seen from equation (1), the baseline current changes if the temperature of the cooling head 215 changes. That is, the signal pulse ΔI changes when the temperature of the cooling head 215 changes.

[0054] The signal pulse ΔI, when the TES 201 is irradiated, changes in an increasing direction according to the formula (2) described above with the increase in the current flowing through the SQUID amplifier 207 (equal to the TES current It). The signal pulse ΔI is convolved with the filter by the pulse height analyzer 251, and the peak value calculated from this is corrected by the correction unit 252 and transferred to the spectrum generator 253. The spectrum generator 253 then produces the spectrum, with the horizontal axis indicating the peak value and the vertical axis indicating the count value. For example, if the peak value is 100, one is counted at position 100.

[0055] The fact that the signal pulse varies despite irradiation with radiation of the same energy means that the peak value fluctuates. The degree of this fluctuation corresponds to the energy resolution described above. This means that to achieve high energy resolution, the fluctuation of the peak value with respect to radiation of the same energy must be reduced.

[0056] When the TES 201 is maintained in the intermediate state between normal conductivity and superconductivity, the Joule heating generated in the second thermometer 213 is in thermal equilibrium with the heat flowing through the membrane 214 to the cooling head 215. The thermal equilibrium between the Joule heating and the heat flow is given by the formula (1) described above. Here, the formula (1) described above is rewritten as the following formula (3), taking into account that the TES current It is influenced by the heat Pex from outside the TES 201: [Formula 3] It2Rt(T)+(V+GTIα)δIt+Pex=G(T−Tb)

[0057] When the heat Pex from outside the TES 201 increases, δIt in the second term on the left-hand side decreases, so that formula (3) is satisfied. This means that the baseline current changes when the heat Pex from outside the TES 201 changes, and that the signal pulse ΔI changes when the baseline current changes. Because the peak value changes when the signal pulse ΔI changes, the energy resolution is affected. Exemplary variations in the heat Pex from outside the TES 201 include a temperature change of the cooling head 215, a change in thermal radiation due to a temperature change in the heat shield 217 surrounding the cooling head 215, a change in thermal conductivity from the heat shield 217 to the TES 201 due to residual gas present in the cooler 211, or the like. <Betrieb des Strahlungsanalyse-Untersystems>

[0058] Accordingly, the present embodiment uses the peak correction method described below. In summary, the correction unit 252 acquires the baseline current and the peak value during irradiation with radiation of a predetermined energy (first energy) under at least two different temperature conditions and stores them in advance as correlation data (before the start of the analysis). When the actual radiation is analyzed (when the scanning electron microscope system 100 is in operation), the correction unit 252 measures the baseline current normally flowing through the TES 201 immediately before the TES 201 acquires the signal pulse. Then, an accurate peak value can be obtained by correcting the peak value of the signal pulse using the previously acquired correlation data between the baseline current and the peak value.It should be noted that the correlation data need only be based on the baseline current and the peak value, and that the baseline current and the energy value calculated from the peak value can be taken as correlation data.

[0059] The baseline current has a statistical fluctuation because it is a current that normally flows through the TES 201. Therefore, for example, approximately 100 sampled data points can be averaged and the averaged value used. It is possible, for instance, to monitor a current value that is the output of the room temperature amplifier 208 using a 1 ms / s analog-to-digital converter (ADC), to acquire several data points at a 1 µs sampling interval, and to average them.

[0060] In the radiation analysis subsystem 200, by suppressing the change in the baseline current during the operation of the scanning electron microscope system 100 (during sample analysis) within ±2.0 µA, the change in the measured radiation energy can be reduced to a maximum of 1 eV, which is used as the bin width of the energy spectrum, and a consistently high energy resolution can be obtained. (Measurement preparation: Collecting correlation data)

[0061] Fig. Figure 5 is a flowchart of a measurement preparation procedure executed by the radiation analysis subsystem 200. The correlation data mentioned are obtained during this measurement preparation. Although the in Fig. Since the work process described in section 5 is actually performed by the computer subsystem 250, which executes a program to implement the function of the respective modules, any module of the computer subsystem 250 can be taken as the subject of each work process in the description below.

[0062] During measurement preparation, the TES 201 must be irradiated with radiation of the same energy (energy E0 (first energy)). The energy of the radiation entering the TES 201 is determined by an element contained in sample 306, which is placed on sample stage 307 of the [system name missing]. Fig. The scanning electron microscope 300 is arranged as shown in Figure 1. Accordingly, the measurement preparation is carried out using the sample 306, whereby radiation with the desired energy E0 can be obtained. For example, a sample for measurement preparation and a sample to be viewed by the scanning electron microscope 300 can be arranged on the sample stage 307. The element to be irradiated with the electron beam 302 can be changed by moving the sample stage 307 in the XY direction using a sample containing several element types for measurement preparation. Alternatively, the element to be irradiated with the electron beam 302 can be changed by scanning the sample for measurement preparation, which contains several element types, using the deflection coil 304 with the electron beam 302. For example, if silicon is irradiated with the electron beam 302, radiation with an energy of 1740 eV is generated.

[0063] First, the computer subsystem 250 confirms, based on the temperature detected by the first thermometer 209, that the cooler 211 is being cooled sufficiently. The temperature control unit 254 then sets a reference temperature of T0 and adjusts the output of the heater 210 based on the temperature detected by the first thermometer 209. Once the temperature of the cooling head 215 reaches T0, the output of the first thermometer 209 fluctuates around the temperature T0.

[0064] In step S11, the temperature control unit 254 confirms that the temperature change received from the first thermometer 209 has been reduced to less than ±0.1 mK, and the correction unit 252 confirms that the change in baseline current has been reduced to less than ±0.2 µA.

[0065] In step S12, after detecting the signal pulse resulting from irradiation with radiation having energy E0, the pulse height analyzer 251 calculates the peak value and outputs it as peak value PH0 to the correction unit 252. The correction unit 252 stores the baseline current BL0 and the peak value PH0 at this time as correlation data.

[0066] In step S13, the temperature control unit 254 adjusts the output of the heater 210 by changing the setpoint temperature to T+ and increases the temperature such that the baseline current is approximately 2.0 µA greater than BL0. The temperature control unit 254 confirms that the temperature change has become less than ±0.1 mK, and the correction unit 252 confirms that the change in the baseline current has become less than ±0.2 µA.

[0067] In step S14, after detecting the signal pulse resulting from irradiation with radiation having energy E0, the pulse height analyzer 251 calculates the peak value and outputs it as peak value PH+ to the correction unit 252. The correction unit 252 stores the baseline current BL+ and the peak value PH+ at this time as correlation data.

[0068] In step S15, the temperature control unit 254 changes the setpoint temperature to T-, adjusts the output of the heater 210, and reduces the temperature such that the baseline current is approximately 2.0 µA lower than BL0. The temperature control unit 254 confirms that the temperature change has become less than ±0.1 mK, and the correction unit 252 confirms that the change in the baseline current has become less than ±0.2 µA.

[0069] In step S16, after detecting the signal pulse resulting from irradiation with radiation having energy E0, the pulse height analyzer 251 calculates the peak value and outputs it as peak value PH- to the correction unit 252. The correction unit 252 stores the baseline current BL- and the peak value PH- at this time as correlation data.

[0070] In step S17, the temperature control unit 254 adjusts the output of the heater 210 so that the temperature is at a reference value T0. The temperature control unit 254 confirms that the temperature change has become less than ±0.1 mK. This completes the measurement preparation and enables analysis with a consistently high energy resolution.

[0071] Fig. Figure 6 is a graph showing the change in baseline current from the beginning to the end of the measurement preparation. Fig. Figure 6 indicates the horizontal axis as time and the vertical axis as the baseline current. In the Fig. In the example shown in Figure 6, the baseline current BL0 at the setpoint temperature T0 is 10 µA, the baseline current BL+ at the setpoint temperature T+ is 12 µA, and the baseline current BL- at the setpoint temperature T- is 8 µA. The Fig. The graph shown in Figure 6 can be displayed on the display unit of computer subsystem 250 or on the display unit 507 of computer subsystem 500.

[0072] Furthermore, the display unit of the computer subsystem 250 can show the user a GUI screen display for entering the energy E0 of the radiation, the set temperatures T0, T+ and T- of the temperature control unit 254, which were set in the aforementioned measurement preparation, and for displaying the recorded correlation data.

[0073] Fig. Figure 7 is a schematic diagram of a correlation data acquisition screen display 255 (GUI screen display) for measurement preparation. As in Fig. As shown in Figure 7, the correlation data acquisition screen display 255 has an input box for, for example, three temperatures (T0, T+, T-) and for the energy of the radiation (E0) to be entered by a user. The correlation data acquisition screen display 255 has a start button, and when the user clicks the start button, the computer subsystem 250 performs the measurement preparation according to the instructions in Figure 7. Fig. The system analyzes the flowchart shown in Figure 5 and records the correlation data between the baseline flow and the peak value. Computer subsystem 250 displays the obtained correlation data between the baseline flow and the peak value on the correlation data acquisition screen display 255. Because the correlation data acquisition screen display 255 allows the user to confirm the correlation data between the baseline flow and the peak value in this way, the system is made user-friendly. (Method for correcting the peak value in the analysis of radiation)

[0074] The following describes a method for correcting the peak value in the analysis of radiation with unknown energy (second energy).

[0075] Fig. Figure 8 is a flowchart of the procedure for correcting the peak value using the correction unit 252. As described above, the baseline current can be less affected by fluctuations if approximately 100 sampled data points are averaged and the averaged value is used. Accordingly, in step S21, the correction unit 252 acquires one point of current value sampled at each µs, acquiring the current value sampled from a total of 110 points.

[0076] In step S22, the correction unit 252 captures a point of the current value sampling data. In step S23, the correction unit 252 determines whether the last current value captured in step S22 exceeds a threshold and whether the signal pulse is detected. Steps S22 and S23 are repeated until the signal pulse is detected.

[0077] If the last current value exceeds the threshold (Yes), the process continues in step S24, where the correction unit 252 calculates the average value of a total of 100 current values ​​from 110 points before the threshold is exceeded up to 11 points before it is exceeded, with the average value being considered the baseline current BL.

[0078] Fig. Figure 9 is a graph showing the change in the current detected by the correction unit 252. Fig. 9. The horizontal axis indicates the count of sampled points, and the vertical axis indicates the baseline current. In the Fig. In the example shown, the current value exceeds the threshold at point 526 and the baseline current BL is 9.042 µA when an average value is taken from point 416 to point 515.

[0079] To Fig. Returning to point 8, it should be noted that the correction unit 252 determines the peak value PH of the signal pulse as a result of irradiation with the radiation having the unknown energy, using the baseline current BL detected at the same time and the value previously determined by the in Fig. The five described methods correct the recorded correlation data. In particular, an accurate peak value PH' is calculated after correlation using the baseline current (BL0, BL+, BL-) recorded during measurement preparation and the peak value (PH0, PH+, PH-) of the signal pulse of the radiation with energy E0.

[0080] The correction unit 252 first calculates the peak value PH0' of the radiation with energy E0 when the baseline current is B0, using the following formula (4). The correction unit 252 then calculates the post-correction peak value PH' using a relationship where the ratio between the peak value PH and the peak value PH0' is equal to the ratio between the peak value PH' and the peak value PH0, using the following formula (5). The correction unit 252 or the spectrum generating unit 253 can determine the value of the unknown energy by converting the post-correction peak value PH' into the energy. [Formula 4] PH0'={PH0+PH+−PH0BL+−BL0×(BL−BL0)(BL≥BL0)PH0−PH0−PH−BL0−BL−×(BL0−BL)(BL <BL0) [Formula 5] PH'=PH0PH0'×PH

[0081] Fig. Figure 10 shows an example of the correlation data between the baseline current and the peak value of the signal pulse of the radiation with energy E0 and a relationship between PH0, PH0', PH and PH'. Fig. In figure 10, the horizontal axis indicates the baseline current and the vertical axis indicates the peak value. As in Fig. As shown in Figure 10, although the correlation data are approximated using three data points, there can be at least two data points for recording the correlation data. It should be noted that, as described above, the correction unit 252 in step S24, when the energy calculated from the peak value (PH0, PH+, PH-) and the peak value (PH0, PH+, PH-) is used as correlation data, can obtain the post-correction energy value by correcting the energy value calculated from the peak value PH.

[0082] To Fig. Returning to point 8, it should be noted that in step S25, for example, the correction unit 252 captures 900 points of the current value sampling data to wait until the current flowing through the TES 201 returns to its static state.

[0083] In step S26, the correction unit 252 captures a point of the current value sampling data. In step S27, the correction unit 252 determines whether the last current value is lower than the threshold. Steps S26 and S27 are repeated until the last current value is lower than the threshold.

[0084] If step S27 determines that the last current value is lower than the threshold (Yes), the process returns to step S21 and performs the same process as described above.

[0085] The above-described method for correcting the peak value according to the present embodiment is applicable if the energy of the radiation entering the TES 201 is proportional to the peak value of the signal pulse of the TES 201.

[0086] Fig. Figure 11 is a graph showing an example of the correlation data when the energy of the radiation entering the TES 201 is proportional to the peak value. Fig. Figure 11 indicates the energy of the radiation on the horizontal axis and the peak value on the vertical axis. As in Fig. As shown in Figure 11, the ratio between the peak values ​​PH0, PH+, and PH- of the signal pulse remains constant regardless of the energy value if the radiation energy is proportional to the peak value. Accordingly, it is possible to acquire the correlation data using radiation with energy E0 and to calculate the peak value PH' after correction, as described above using formulas (4) and (5). <Technische Wirkung>

[0087] As described above, the radiation analysis subsystem 200, according to the present embodiment, corrects the peak value according to the baseline current flowing through the TES 201 immediately before the peak value is measured during the actual analysis by the pulse height analyzer 251, using the previously obtained correlation data based on the baseline current and the peak value. Because this makes it possible to obtain a constant peak value regardless of a change in the baseline current with respect to the radiation with the same energy, without acquiring the additional correction data, a consistently high energy resolution can be maintained. Second embodiment

[0088] In the first embodiment, the technology for peak correction was described based on the assumption that the energy of the radiation entering the TES 201 is proportional to the peak value of the TES 201 signal pulse. However, in an actual radiation analyzer, the energy of the radiation may not be proportional to the peak value of the signal pulse. Even in such a case, it is possible to obtain an accurate peak value by first obtaining correlation data based on the energy of the radiation and the peak value of the signal pulse. Accordingly, a second embodiment proposes a procedure for the operation of the radiation analysis subsystem in a case where the energy of the radiation is not proportional to the peak value.

[0089] The configuration of the radiation analysis subsystem according to the present embodiment can be the same as the configuration according to the first embodiment, therefore its description is omitted. <Betrieb des Strahlungsanalyse-Untersystems> (Measurement preparation: Collecting correlation data)

[0090] Fig. Figure 12 is a graph showing an example of the correlation data when the energy of the radiation entering the TES 201 is not proportional to the peak value. Fig. In figure 12, the horizontal axis indicates the energy of the radiation and the vertical axis indicates the peak value. As in Fig. As shown in Figure 12, the correlation data must be collected using radiations with two or more energies if the energy of the radiation is not proportional to the peak value.

[0091] The method for acquiring the correlation data according to the present embodiment is essentially the same as that of the first embodiment (flowchart in the following points), except for the following. Fig. 5) This means that when the pulse height analyzer 251 receives the peak value (PH0, PH+, PH-) during the acquisition of the correlation data (steps S12, S14 and S16), it detects the signal pulse corresponding to the two or more radiation energies, and the correction unit 252 stores the peak value. The energy of the radiation can be changed by altering the sample 306 (of the element) to be irradiated with the electron beam 302 by moving the sample stage 307 of the Fig. The scanning electron microscope 300 shown in 1 can be modified, or by scanning with the scanning coil 304. In addition, the correction unit 252 generates a correction curve (function f0, f+, f-) of the data, including the detected radiation energy and the peak value interpolated by a function of nth order (n is a natural number) or a spline curve, and stores the correction curve as correlation data.

[0092] Fig. Figure 13 shows a correlation data acquisition screen display 256 (GUI screen display) for acquiring correlation data according to the second embodiment. As in Fig. As shown in Figure 13, the correlation data acquisition screen display 256 is a GUI screen display for acquiring the baseline current and the correlation data between the radiant energy and the peak value and has an input box, for example, for entering three temperatures (T0, T+, T-), two or more radiant energies and an interpolation method.

[0093] For example, up to approximately 20 radiation energies can be specified. The in Fig. The correlation data acquisition screen 256, shown in Figure 13, is designed to allow the setting of nine energies. Furthermore, the interpolation method can be selected, for example, either the nth-order function (n being a natural number) or the spline curve. The correlation data acquisition screen 256 is equipped with a start button, and when the user clicks the start button, the computer subsystem 250 performs the measurement preparation according to the procedure described in Figure 13. Fig. The computer subsystem 250 extracts the flow diagram shown in section 5 and stores the baseline current and peak values ​​for all radiant energies. It then generates the correction curve for the radiant energy and peak value and stores this correction curve as correlation data. The computer subsystem 250 displays the acquired baseline current and the correlation data for the radiant energy and peak value for each baseline current on the correlation data acquisition screen display 256. (Method for correcting the peak value in the analysis of radiation)

[0094] The method for acquiring the correlation data according to the present embodiment is essentially the same as that of the first embodiment (flowchart in the following points), except for the following. Fig. 8).

[0095] The correction unit 252 corrects the peak value PH of the signal pulse of the radiation with unknown energy E (second energy), measured by the pulse height analyzer 251, in the following manner using the baseline current BL measured at the same time and the correlation data. Specifically, the exact peak value PH' after correction is calculated using the baseline current (BL0, BL+, BL-) recorded during measurement preparation and the correction curve of the radiation energy and the peak value at each baseline current (function f0, f+, f-). At this time, the relationship between the unknown energy E and the peak value PH is given by the following formula (6). The correction unit 252 then calculates the peak value PH' after correction using the inverse function of the correction curve, according to the following formula (7): [Formula 6] E={f+(PH)(BL=BL+)f0(PH)(BL=BL0)f−(PH)(BL=BL−) [Formula 7] PH'={f0−1(f0(PH)+f+(PH)−f0(PH)BL+−BL0×(BL−BL0))(BL≥BL0)f0−1(f0(PH)−f0(PH)−f−(PH)BL0−BL×(BL0−BL))(BL <BL0)

[0096] In formula (7), the expression in parentheses after f0 gives -1 It is suggested that if a single radiation is detected, the energy value of the radiation can be calculated from the peak value of the pulse and the baseline current. Formula (7) is used to calculate an accurate peak value PH' after correction using the inverse function of the energy value. <Technische Wirkung>

[0097] As described above, the radiation analysis subsystem according to the second embodiment obtains the peak values ​​at 254, confirms at least two baseline currents with respect to each energy value using radiations with at least two known energy values, and thereby obtains the correlation data (correction curve) of the peak value and the energy value. This correlation data is used to correct the peak value according to the baseline current flowing through the TES immediately before the peak value is measured by the pulse height analyzer. This allows a constant peak value with respect to radiation with the same energy to be obtained regardless of changes in the baseline current, without acquiring the additional correction data, thus ensuring consistently high energy resolution. modification

[0098] The present disclosure is not limited to the embodiments mentioned above, but may include various modifications. For example, the aforementioned embodiments have been described in detail for ease of understanding of the present disclosure, and the invention does not necessarily include all configurations described herein. A part of one embodiment may be replaced by a configuration of another embodiment. A configuration of one embodiment may also be added to a configuration of another embodiment. Moreover, a part of a configuration of one embodiment may be added to, removed from, or replaced by a part of the configuration of another embodiment.

[0099] It goes without saying that, although each of the above-described configurations, functions, control units, or the like has been described with reference to an example for generating a program for implementing it or a part thereof, it or a part thereof can be implemented in hardware, for example, by designing an integrated circuit. That is to say, the function of the control unit, or a part thereof, can be implemented, for example, not by a program, but by an integrated circuit such as an ASIC (application-specific integrated circuit), an FPGA (field-programmable gate array), and the like. Reference symbol list 100 scanning electron microscope systems 200 Radiation Analysis Subsystem 201 TES 202 Sensor circuit unit 203 Bias power source 204 Shunt resistor 205 Input coil 206 Current sensing mechanism 207 SQUID amplifiers 208 Room temperature amplifiers 209 first thermometer 210 Heating 211 coolers 212 absorbers 213 second thermometer 214 Membran 215 Cooling head 216 superconducting wiring 217 Heat shielding 250 computer subsystem 251 Pulse height analyzer 252 correction units 253 Spectrum generation unit 254 Temperature control unit 255, 256: Correlation data acquisition screen display 300 scanning electron microscope 301 Electron source 302 Electron beam 303 Converging lens 304 Deflection coil 305 lens 306 Sample 307 Sample table 308 Backscattered electron detector 309 Secondary electron detector 400 High-voltage supply 500 computer subsystem 501 Total Control Unit 502 Control unit for the electron-optical system 503 Table control unit 504 A / D conversion unit 505 Image Operating Unit 506 Storage device 507 Display unit 508 Input device

Claims

[1] Radiation analysis system comprising: a superconducting transition edge sensor (201) that detects radiation, a current sensing mechanism (206) that detects a current flowing through the superconducting transition edge sensor (201), and a computer subsystem (250) that processes a current detection signal from the current detection mechanism (206), the computer subsystem (250) performs the following: a process for calculating a baseline current of the current detection signal, a process for calculating a peak value of a signal pulse generated in the detection signal when the superconducting transition edge sensor (201) detects the radiation, a process for acquiring correlation data based on the baseline current and the peak value when radiation with multiple energies is detected under two or more different temperature conditions by the superconducting transition edge sensor (201), and a process for correcting the peak value of the signal pulse or an energy value calculated from the peak value based on the baseline current before the signal pulse is generated when radiation of unknown energy is detected by the superconducting transition edge sensor (201) and the correlation data. [2] Radiation analysis system according to claim 1, wherein the computer subsystem (250) further performs a calculation of the unknown energy based on the corrected peak value. [3] Radiation analysis system comprising: a superconducting transition edge sensor (201) that detects radiation, a current detection mechanism (206) that detects a current flowing through the superconducting transition edge sensor (201), a cooling head (215) for cooling the superconducting transition edge sensor (201), a heater (210) provided for the cooling head (215), and a computer subsystem (250) that processes a current detection signal from the current detection mechanism (206), the computer subsystem (250) performs the following: a process for controlling the output of the heating (210), a process for calculating a baseline current of the current detection signal, a process for calculating a peak value of a signal pulse generated in the detection signal when the superconducting transition edge sensor (201) detects the radiation, a process for acquiring correlation data based on the baseline current and the peak value when radiation with at least one first energy is detected by the superconducting transition edge sensor (201) under two or more different temperature conditions, and a process for correcting the peak value of the signal pulse or an energy value calculated from the peak value based on the baseline current before the signal pulse is generated when radiation with an unknown energy is detected by the superconducting transition edge sensor (201), and the correlation data, wherein the computer subsystem (250) controls the output of the heater (210) during the process of acquiring the correlation data such that a temperature change in the cooling head (215) is less than or equal to ±0.1 mK. [4] Radiation analysis system according to claim 3, wherein the computer subsystem (250) controls the output of the heater (210) during the process of acquiring the correlation data such that a change in the baseline current is less than or equal to ±0.2 µA. [5] Radiation analysis system comprising: a superconducting transition edge sensor (201) that detects radiation, a current detection mechanism (206) that detects a current flowing through the superconducting transition edge sensor (201), a cooling head (215) for cooling the superconducting transition edge sensor (201) and a heater (210) provided for the cooling head (215), and a computer subsystem (250) that processes a current detection signal from the current detection mechanism (206), the computer subsystem (250) performs the following: a process for controlling the output of the heating (210), a process for calculating a baseline current of the current detection signal, a process for calculating a peak value of a signal pulse generated in the detection signal when the superconducting transition edge sensor (201) detects the radiation, a process for acquiring correlation data based on the baseline current and the peak value when radiation with at least one first energy is detected by the superconducting transition edge sensor (201) under two or more different temperature conditions, and a process for correcting the peak value of the signal pulse or an energy value calculated from the peak value based on the baseline current before the signal pulse is generated when radiation with an unknown energy is detected by the superconducting transition edge sensor (201), and the correlation data, wherein the computer subsystem (250) controls the output of the heater (210) such that a change in the baseline current is less than or equal to ±2.0 µA. [6] Radiation analysis system according to one of the preceding claims, wherein the computer subsystem (250) has a display unit and wherein the computer subsystem (250) displays a GUI screen display for capturing the correlation data on the display unit. [7] Radiation analysis system according to any of the preceding claims, wherein the current detection mechanism (206) comprises: a superconducting quantum interference amplifier (207) and a room temperature amplifier (208) for amplifying and shaping an electrical signal output by the superconducting quantum interference amplifier (207). [8] System operating with a beam of charged particles, comprising a radiation analysis system (200) according to any of the preceding claims. [9] Radiation analysis methods, comprising: Detection of radiation by a superconducting transition edge sensor (201), Detection of a current flowing through the superconducting transition edge sensor (201) by a current detection mechanism (206), Calculating a baseline current of the current through a computer subsystem (250), Calculating (S12) a peak value of a signal pulse generated in the detection signal by the computer subsystem (250) when the superconducting transition edge sensor (201) detects the radiation, Acquisition (S14) of correlation data based on the baseline current and the peak value by the computer subsystem (250) when radiation with multiple energies is detected under two or more different temperature conditions by the superconducting transition edge sensor (201), and Correcting (S16) the peak value of the signal pulse or an energy value calculated from the peak value on the basis of the baseline current before the signal pulse is generated when radiation of unknown energy is detected by the superconducting transition edge sensor (201) and the correlation data by the computer subsystem (250). [10] Radiation analysis system comprising: a superconducting transition edge sensor (201) that detects radiation, a current sensing mechanism (206) that detects a current flowing through the superconducting transition edge sensor (201), and a computer subsystem (250) that processes a current detection signal from the current detection mechanism (206), wherein the computer subsystem (250) includes a storage device that stores correlation data based on a baseline current and a peak value when radiation with multiple energies is detected under two or more different temperature conditions by the superconducting transition edge sensor (201), and the computer subsystem (250) performs the following: a process for calculating a baseline current of the current detection signal, a process (S12) for calculating a peak value of a signal pulse generated in the detection signal when the superconducting transition edge sensor (201) detects the radiation, and a process (S16) for correcting the peak value of the signal pulse or an energy value calculated from the peak value on the basis of the baseline current before the signal pulse is generated when radiation of unknown energy is detected by the superconducting transition edge sensor (201) and the correlation data. [11] Radiation analysis system comprising: a superconducting transition edge sensor (201) that detects radiation, a current detection mechanism (206) that detects a current flowing through the superconducting junction sensor (201), and a computer subsystem (250) that processes a current detection signal from the current detection mechanism (206), the computer subsystem (250) performs the following: a process for calculating a baseline current of the current detection signal, a process for calculating a peak value of a signal pulse generated in the detection signal when the superconducting transition edge sensor (201) detects the radiation, a process for acquiring correlation data based on the baseline current and the peak value when radiation with multiple energies is detected under two or more different temperature conditions by the superconducting transition edge sensor (201), and a process for calculating an average value of the baseline currents from a point before a first point to a second point before a point where the threshold is exceeded if the baseline current exceeds a threshold before the signal pulse is generated when radiation of unknown energy is detected by the superconducting transition edge sensor (201), and correcting the peak value of the signal pulse or an energy value calculated from the peak value on the basis of the average value of the baseline currents and the correlation data.

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