Analysis system, spectrum generation method, and signal processing device

Abstract

In an analysis system (100), a detector (50) is configured to detect the count of electrons with respect to each of a plurality of channels respectively corresponding to a plurality of energy bands. With respect to the count of each of the plurality of channels, a processing device (60) calculates a correction value by performing a first correction using first dead time corresponding to all of the plurality of channels and a second correction using second dead time corresponding to each of the plurality of channels, and generates an energy spectrum on the basis of the correction value of each of the plurality of channels.

Description

Analysis System, Spectrum Generation Method, and Signal Processing Apparatus

[0001] The present invention relates to an analysis system, a spectrum generation method, and a signal processing apparatus.

[0002] Surface analysis is an analysis for clarifying the structure and composition of the surface and interface of a sample by applying a stimulus to the sample and analyzing the detected response. As a surface analysis method, for example, there is X-ray photoelectron spectroscopy as disclosed in Japanese Patent Application Laid-Open No. 2001-201470 (Patent Document 1). Also, in surface analysis including X-ray photoelectron spectroscopy, a delay line detector (DLD: delay line detector) may be used to detect pulsed radiation or electrons emitted from a sample.

[0003] Japanese Patent Application Laid-Open No. 2001-201470

[0004] A detector for charged particles such as electrons, like the DLD, requires a certain amount of time until the next signal can be detected after a signal is detected. This time is called the dead time. And in an apparatus using such a detector (for example, an X-ray photoelectron spectrometer (XPS)), so-called dead time correction is performed in which the true signal amount is calculated by estimating the signal amount that entered during the dead time and was not detected from the detected signal amount. And in a system including a detector for charged particles, improvement in the accuracy of dead time correction is desired.

[0005] The present invention has been conceived in view of such circumstances, and its object is to provide a technique for improving the accuracy of dead time correction in an analysis system using a DLD.

[0006] An analytical system according to a certain aspect of the present disclosure comprises an X-ray source for irradiating a sample with X-rays, an energy spectrometer for spatially separating electrons according to the kinetic energy of electrons emitted from the sample, a detector for detecting the number of electrons that have passed through the energy spectrometer, and a processing device configured to generate an energy spectrum relating to the sample based on the detection results of the detector, wherein the detector is configured to detect the number of electrons for each of a plurality of channels corresponding to each of a plurality of energy bands, and the processing device is configured to calculate a correction value by performing a first correction using a first dead time corresponding to all of the plurality of channels and a second correction using a second dead time corresponding to each of the plurality of channels for the count of each of the plurality of channels, and to generate an energy spectrum based on the correction value of each of the plurality of channels.

[0007] A spectrum generation method according to a certain aspect of the present disclosure is a method for generating an energy spectrum relating to a sample based on the detection result of electrons emitted from the sample irradiated with X-rays and passing through an energy spectrometer by a count detector, wherein the detector is configured to detect the electron count for each of a plurality of channels corresponding to each of a plurality of energy bands, and the method comprises the steps of: performing a first correction corresponding to all of the plurality of channels for each count of the plurality of channels; calculating a correction value for each count of the plurality of channels by performing a second correction corresponding to each of the plurality of channels for each count of the plurality of channels; and generating an energy spectrum based on each correction value of the plurality of channels.

[0008] A signal processing device according to the aspects of this disclosure is a signal processing device for a charged particle detector including a microchannel plate (MCP) and a delay line detector (DLD), configured to generate a histogram that counts events for each arrival time difference of electrical pulses output from both ends of the wires of the delay line detector, and configured to perform a two-stage dead time correction using a first dead time obtained from the total count of the histogram and a second dead time obtained from the count for each channel of the histogram.

[0009] In accordance with certain aspects of this disclosure, a technique is provided to improve the accuracy of dead time correction in an analysis system that utilizes DLD.

[0010] This figure shows the configuration of the XPS 100 according to the embodiment. This figure illustrates the configuration of the detector 50. This figure illustrates a specific example of the configuration of the detector 50. This figure shows an example of an energy spectrum. This figure shows an example of a histogram used to generate the energy spectrum. This figure illustrates the factors causing dead time in the entire MCP. This figure shows an example of a set of relational equations for determining dead time. This figure illustrates one method of correcting the count number of each channel. This figure illustrates the content of the first correction. This figure shows another example of a model used for correcting the count number. This is a flowchart of the process for generating the energy spectrum of a sample, which is performed in the XPS 100.

[0011] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0012] [Configuration of the Analysis System] Figure 1 shows the configuration of the XPS100 according to an embodiment. The XPS100 is an example of an analysis system. The XPS100 measures the kinetic energy distribution of photoelectrons emitted by irradiating a sample S with X-rays, and obtains information on the types, amounts, and chemical bonding states of elements present on the surface of the sample S. Referring to Figure 1, the XPS100 includes an X-ray source 10, a lens 20, a slit 30, an energy spectrometer 40, a detector 50, and a processing device 60.

[0013] The X-ray source 10 is configured to generate X-rays and irradiate the sample S with the generated X-rays. The X-ray source 10 includes, for example, a filament and an anode plate. The anode plate is made of a metallic material such as aluminum, magnesium, chromium, or copper. When a voltage is applied to the filament, thermionic electrons are emitted from the filament. Thermionic electrons are accelerated by the voltage applied between the filament and the anode plate. When the accelerated thermionic electrons collide with the anode plate, X-rays are generated from the anode plate. When the generated X-rays irradiate the sample S, the inner-shell electrons of elements present near the surface of the sample S are excited, and photoelectrons are emitted. The electrons emitted from the sample S are not limited to photoelectrons, but may also be Auger electrons. In Figure 1, line L1 shows the movement of electrons emitted from the sample S.

[0014] Lens 20 receives electrons emitted from the sample S, slows them down, and focuses them. Lens 20 includes, for example, an electrostatic lens and a deceleration lens. The electrostatic lens focuses the electrons towards the entrance 31 of the slit 30. The deceleration lens slows down the electrons incident on the energy spectrometer 40.

[0015] The energy spectrometer 40 spatially separates electrons according to their kinetic energy when emitted from the sample S. The energy spectrometer 40 includes an outer hemispherical electrode 41 and an inner hemispherical electrode 42. The energy spectrometer 40 applies a voltage to the outer hemispherical electrode 41 and the inner hemispherical electrode 42, generating an electric field between them. This electric field bends the flight path of electrons that have passed through the slit 30. Electrons that have passed through the energy spectrometer 40 are incident on the detector 50. The potential difference between the outer hemispherical electrode 41 and the inner hemispherical electrode 42 corresponds to the kinetic energy of electrons that can pass through the energy spectrometer 40. In Figure 1, the energy spectrometer 40 is an electrostatic hemispherical electron energy spectrometer, but the energy spectrometer 40 is not limited to an electrostatic hemispherical electron energy spectrometer as long as it spatially separates electrons according to their kinetic energy when incident on them.

[0016] The detector 50 detects electrons that have passed through the energy spectrometer 40. By adjusting the potential difference between the outer hemispherical electrode 41 and the inner hemispherical electrode 42, the kinetic energy of electrons that can pass through the energy spectrometer 40 is changed.

[0017] Figure 2 is a diagram illustrating the configuration of the detector 50. As shown in Figure 2, the detector 50 includes a micro-channel plate (MCP) 51 and a delay line detector (DLD) 52.

[0018] The MCP51 has a structure consisting of bundled miniature photomultiplier tubes and amplifies incident charged particles. Electrons incident from the front surface 51X are amplified by the MCP51, and multiple electrons are then emitted from the back surface 51Y.

[0019] The DLD 52 detects the position of electrons emitted from the MCP 51. The DLD 52 has a structure in which a conductor (collector wire 52X, which will be described later with reference to Figure 3) is wound around it. When electrons emitted from the MCP 51 collide with the conductor, as indicated by arrow L2, a charge flows from the collision point toward both ends of the conductor. This charge flow is detected as the movement of an electrical pulse P.

[0020] The time it takes for charge to reach both ends of a wire differs depending on the location of the electron collision. Specifically, the charge reaches the end of the wire closer to the collision location faster than the end of the wire further away from the collision location. For example, if an electron emitted from the back surface 51Y hits position P on the DLD 52, charge V1 will go towards terminal 52A of the DLD 52, and charge V2 will go towards terminal 52B, which is located on the opposite side of terminal 52A. The difference in the time it takes for the charge to reach the terminals provides information about the location of the electron collision.

[0021] Terminals 52A and 52B are connected to the processing unit 60. The processing unit 60 identifies the location of the electron collision based on the difference between the time it takes for charge V1 to reach terminal 52A and the time it takes for charge V2 to reach terminal 52B, and identifies the energy of the electron based on the identified location. The processing unit 60 includes a dedicated circuit (e.g., an ASIC (Application Specific Integrated Circuit)) or processor for processing the acquired information. In the processing unit 60, the dedicated circuit or processor is an example of a processing circuit, and the processing described herein is realized either as a function of the dedicated circuit or by the processor executing a given program non-temporarily stored in a memory device within the processing unit 60. The processing unit 60 may be configured separately from the XPS 100 main unit. The processing unit 60 is an example of a “signal processing unit”.

[0022] Figure 3 is a diagram illustrating a specific example of the configuration of the detector 50. As shown in Figure 3, in the detector 50, the MCP 51 is a plate-shaped element. The element includes a bundle of numerous glass tubes (the "photomultiplier tubes" mentioned above). Each glass tube has an inner diameter of about 10 μm. The bundle of glass tubes is cut to a thickness of about 2 mm on a surface inclined at about 8°, thus forming the element.

[0023] In Figure 3, the MCP51 has a front surface 51X and a back surface 51Y. In the MCP51, electrons incident on the front surface 51X enter one of the glass tubes constituting the bundle, strike the inner wall of that glass tube and generate secondary electrons. A voltage is applied to the MCP51 from the front surface 51X toward the back surface 51Y to accelerate the electrons. Therefore, the secondary electrons generated as described above are accelerated, collide with the inner wall of the glass tube, and generate even more secondary electrons. By repeating this process, 10 ７ A few electrons are released.

[0024] The DLD 52 includes a holder 52Z made of metal, and a collector wire 52X and a reference wire 52Y wound around the holder 52Z with an insulator in between. The collector wire 52X corresponds to the "conductor" described above. The reference wire 52Y is wound around the holder 52Z so as to be parallel to the collector wire 52X. A voltage approximately 50V lower than that of the collector wire 52X is applied to the reference wire 52Y. This ensures that electrons emitted from the MCP 51 are reliably collected by the collector wire 52X.

[0025] In the detector 50, electrons emitted from the MCP 51 reach the collector wire 52X. The electrons then travel along the collector wire 52X, generating two electrical pulses that move toward each end (terminals 52A and 52B). The processing unit 60 determines the position on the collector wire 52X where the electrons arrived by measuring the time difference between the arrival of these two electrical pulses. For example, if the time difference is zero, the center of the collector wire 52X is determined as the position where the electrons arrived. The larger the time difference, the closer the position is to terminal 52A or terminal 52B on the collector wire 52X.

[0026] [Energy Spectrum] In the XPS100, the energy spectrometer 40 strongly bends the orbits of low-energy electrons, while the orbits of high-energy electrons are weakly bent. Therefore, the position where electrons arrive at the exit of the energy spectrometer 40 is affected by the energy level of the electrons introduced into the energy spectrometer 40. The processing unit 60 uses the detector 50 to count the number of electrons arriving at each position at the exit of the energy spectrometer 40, generates a histogram showing the energy distribution, and obtains an energy spectrum from the histogram.

[0027] Figure 4 shows an example of an energy spectrum. In the example in Figure 4, the spectrum is shown when "Ag3d5 / 2" is used as the sample. Various information about the sample (e.g., peak energy) can be obtained from the energy spectrum and used for evaluating the sample. As shown in Figure 4, resolution and signal intensity can also be obtained from the energy spectrum.

[0028] Figure 5 shows an example of a histogram used to generate an energy spectrum. The histogram represents the number of electrons at each arrival position in the DLD 52. The horizontal axis of the histogram in Figure 5 represents channels related to the time difference in electron arrival times between terminal 52A and terminal 52B, which are physical quantities corresponding to the arrival positions. In Figure 5, k is an integer obtained by dividing the time t by a given time interval (100 ps in the example in Figure 5) and rounding up the result, and 2k+1 channels are shown. The values ​​representing the range of each channel ("-450 ps", "-350 ps", "-250 ps", ... "250 ps", "350 ps", "450 ps", etc.) represent values ​​relative to a given reference value. A channel represents a group (time period) related to arrival time. Each channel corresponds to a group consisting of one or more glass tubes of the MCP 51 through which electrons arriving at each time zone pass. In other words, each channel corresponds to one of several energy bands defined for electrons detected by the detector 50.

[0029] The processing unit 60 converts the counts of each channel in the histogram into a count rate. The counts are converted into a count rate by dividing them by the time T required to acquire the histogram. That is, the relationship between the count C(i) of channel i and the count rate V(i) of each channel is expressed by the following equation (1) using the above time T.

[0030] V(i) = C(i) / T …(1) The processing unit 60 also converts the values ​​of each time period in the histogram into corresponding energy values. This converts the histogram representing the relationship between the number of counts and the time period into a histogram representing the relationship between the count rate and energy. By converting the latter histogram into a smooth graph, the processing unit 60 generates a spectrum from the histogram.

[0031] [Count Correction] In detectors using DLDs, two types of factors are assumed to cause dead time. One is that the potential difference between the front and back of the MCP decreases as electrons pass through the glass tube, which temporarily prevents electron multiplication (a factor that occurs in some channels of the MCP). The other is that if the next group of electrons reaches the DLD while an electrical pulse is running along the collector line, the DLD will not be able to detect the correct position, and the signal output from the DLD must be discarded (a factor that occurs in the DLD as a whole).

[0032] Conventionally, no technology has been provided that corrects the count of each channel by taking both of the above two factors into consideration. On the other hand, in the technology described herein, the count is corrected by taking both of these factors into consideration. More specifically, a dead time is determined for each of the two types of factors. In this specification, the corrected value of the count is calculated by performing a correction using one of the two types of dead times (first correction) and a correction using the other (second correction) on the detected count.

[0033] Each of the two factors mentioned above, along with the dead time used in each, will be explained in more detail below.

[0034] <Factors affecting the entire DLD and the first dead time> Position detection in a detector using a DLD is performed by determining the time difference between pulses coming from both sides of the collector wire 52X. However, if a pulse is traveling along the collector wire 52X in response to an electron reaching the MCP 51, and the next pulse is incident on the DLD 52 as the next electron reaches the MCP 51, the arrival order of the four pulses generated by the previous and subsequent pulses may be reversed, making it impossible to detect the correct position.

[0035] Figure 6 is a diagram illustrating the factors causing dead time in the entire MCP. In the example in Figure 6, arrow 80 represents the first electron, and arrow 90 represents the second electron.

[0036] Figure 81 represents the pulse flowing from the collector wire to terminal 52A in response to the first electron, and Figure 82 represents the pulse flowing from the collector wire to terminal 52B in response to the first electron.

[0037] Figure 91 represents the pulse flowing from the collector wire to terminal 52A in response to the second electron, and Figure 92 represents the pulse flowing from the collector wire to terminal 52B in response to the second electron.

[0038] In the example in Figure 6, the first electron (arrow 80) reaches the reference line at a position close to terminal 52A, while the second electron (arrow 90) reaches the reference line at a position close to terminal 52B. As a result, the pulse in Figure 92 reaches terminal 52B before the pulse in Figure 82. In other words, the pulse caused by the later-arriving electron reaches terminal 52B before the pulse caused by the earlier-arriving electron.

[0039] More specifically, the arrival position of the first electron should be determined by the time difference between the detection of the pulse in figure 81 and the pulse in figure 82. However, the DLD 52 cannot distinguish the detection of the pulse in figure 82 from the pulse in figure 92. The DLD 52 mistakenly detects the pulse in figure 92 as the pulse in figure 82. In such cases, the time difference between the detection of the pulse in figure 81 and the pulse in figure 92 is shorter than the shortest interval between pulses expected to determine the arrival position. Therefore, in the XPS 100, if the next pulse is detected within a certain time after the detection of a certain pulse, it is necessary to ignore both "the current pulse" and "the next pulse". The time that represents the period during which detected pulses are ignored in this way is an example of a dead time.

[0040] The dead time described with reference to Figure 6 may be applied to the entire MCP51 (all channels). In this specification, the dead time applied to the entire MCP51 (all glass tubes) may be referred to as the "first dead time τ1".

[0041] <Factors causing issues in some channels of the MCP and the second dead time> In the MCP 51, in each of the one or more glass tubes that make up each channel, charge loss occurs when electrons are multiplied. Until the charge loss is compensated for, the electron multiplication factor decreases in that glass tube. If the next electron is incident on the MCP 51 while the multiplication factor is decreasing, the number of electrons reaching the collector line 52X of the DLD 52 from the MCP 51 decreases, which lowers the height of the electrical pulse obtained from both ends of the collector line 52X. If the height of the electrical pulse becomes too low, it becomes indistinguishable from noise, and counting stops.

[0042] The decrease in the height of the electrical pulse described above occurs only in channels where electrons are continuously incident, and not in other channels.

[0043] As described above, dead time is utilized to compensate for the reduction from the original number of detected electrical pulses due to the continuous incidence of electrons on a certain channel. In this specification, the dead time applied only to some channels may be referred to as "second dead time". More specifically, the dead time applied only to some channels may be referred to as the second dead time τ2.

[0044] <Determination of Dead Time> In one implementation example, the first dead time and the second dead time are each determined by fitting to a previously obtained relational expression.

[0045] FIG. 7 is a diagram showing an example of a set of relational expressions for obtaining the dead time. In FIG. 7, the vertical axis is the output count rate, and the horizontal axis is the input count rate. The input count rate represents the true count rate incident on the detector, and the output count rate represents the count rate of the signals that could be counted by the detector. Although the true count rate incident on the detector cannot be known, FIG. 7 can be drawn by substituting the horizontal axis with some value proportional to it. In one implementation example, the input count rate can be defined by converting the X-ray irradiation intensity of the X-ray source 10 when electrons are input to the energy spectrometer 40 in a given manner.

[0046] In FIG. 7, the relationship between the input count rate and the output count rate calculated by a given model formula for each of the four types of dead times (200 ns, 120 ns, 80 ns, 0 ns) is illustrated.

[0047] To determine the first dead time, the user measures the total count number of the entire MCP 51 for the standard sample with the XPS 100 while changing the X-ray irradiation intensity by the energy spectrometer 40. Thereby, the processing device 60 obtains the relationship between the input count rate and the output count rate for the standard sample. Then, the processing device 60 determines the first dead time by selecting the dead time such that the curve calculated from the obtained relationship and the model formula matches as much as possible.

[0048] To identify the second dead time, the processing unit 60 acquires the relationship between the input count rate and the output count rate for each channel of the standard sample. The processing unit 60 then identifies the second dead time by selecting a dead time such that the acquired relationship and the curve calculated from the model equation match as closely as possible.

[0049] [Specific Example of Count Correction] Figure 8 is a diagram illustrating one method of correcting the count of each channel. In this specification, as one method of implementing correction using a first dead time (first correction) and correction using a second dead time (second correction), the processing device 60 generates an intermediate value from the count of each channel by the first correction, and generates a corrected value from the intermediate value by the second correction.

[0050] In Figure 8, C(i) represents the count of channel i detected by the detector 50. C(ci) represents the intermediate value generated from the count of channel i. C(fi) represents the correction value generated from the intermediate value of channel i.

[0051] The processing device 60 detects photoelectrons emitted from a sample by irradiating the sample with X-rays. The detection result includes the count numbers for each of the multiple channels. The processing device 60 generates the above-mentioned correction values ​​for the count numbers of each channel. Then, the processing device 60 generates the energy spectrum of the sample using the correction values ​​for each channel instead of the count numbers for each channel.

[0052] The first and second corrections will be explained below. (1) First Correction Figure 9 is a diagram illustrating the content of the first correction. Figure 9 shows equations (2) to (5).

[0053] In equation (2), C(i) represents the count of channel i in the detection result of a certain sample. Nout(t) represents the total output count rate of all channels in the above detection result. Nin(t) represents the total input count rate of all channels in the above detection result. And C(ci) represents the median value of channel i in the above detection result. As shown in equation (2), C(ci) is derived by multiplying C(i) by the value obtained by dividing Nin(t) by Nout(t).

[0054] Note that Nout(t) is the sum of the count rates C(i) of all channels. Nin(t) can be obtained from Nout(t) according to a model that defines the relationship between the input count rate and the output count rate.

[0055] Equation (4) and its modified form, equation (5), represent an example of a model. In equations (4) and (5), Nin represents the input count rate, and Nout represents the output count rate. Also, τ represents the dead time. The τ used when generating C(ci) is the dead time common to all channels, i.e., the first dead time τ1.

[0056] By performing the calculations in the order of equation (3) → equation (5) → equation (2), C(ci) can be generated using C(i) and τ1.

[0057] (2) Second Correction In the second correction, C(fi) can be found as Nin by simply substituting τ² for τ and C(ci) for Not in equation (5) in Figure 9.

[0058] [Other Examples of Models] In the example described with reference to Figure 9, models following equations (4) and (5) were used. However, the models used for correcting the count are not limited to those following equations (4) and (5). Figure 10 shows other examples of models used for correcting the count. As shown in Figure 10, models following equation (6) and its modified form, equation (7), may also be used for correcting the count.

[0059] In models according to equations (4) and (5), the dead time is simply doubled if the next electrical pulse occurs during the dead time. Therefore, the dead time may be calculated to be more than it is in reality. In models according to equations (6) and (7), the dead time is not extended even if the next electrical pulse occurs during the dead time. However, in models according to equations (6) and (7), the dead time may be calculated to be less than it is in reality. More complex but more realistic models for calculating dead time are also conceivable. This disclosure does not limit the models to be used. In one implementation, the characteristics of each model are taken into consideration, and different models may be used for the first correction and the second correction.

[0060] [Processing Flow] Figure 11 is a flowchart of the process performed in the XPS 100 to generate the energy spectrum of a sample. In one implementation example, the process in Figure 11 is started when the XPS 100 is instructed to measure the sample, and is performed by the processing device 60.

[0061] In step S10, the processing unit 60 causes the X-ray source 10 to emit X-rays. In step S20, the processing unit 60 uses the detection results of the detector 50 to obtain the electron count for each channel.

[0062] In step S30, the processing unit 60 performs a first correction on the count of each channel.

[0063] In step S40, the processing unit 60 performs a second correction on the count of each channel. The second correction may be performed on the intermediate value generated by performing the first correction on the count. That is, the second correction on the count may be indirectly achieved by performing the second correction on the intermediate value generated from the count.

[0064] In step S50, the processing device 60 generates an energy spectrum of the sample using the correction values ​​for each channel generated by the first and second corrections.

[0065] In step S60, the processing unit 60 outputs the energy spectrum generated in step S50. This output may be achieved by transmitting data representing the energy spectrum to an external device, or by displaying a graphic representing the energy spectrum on a display device. After that, the processing unit 60 terminates the process shown in Figure 11.

[0066] In the process shown in Figure 11, the processing unit 60 may generate a histogram from the counts of each channel in step S20. The processing unit 60 may also correct the histogram in steps S30 and S40, and generate an energy spectrum using the corrected histogram in step S50. The histogram is corrected in two steps by steps S30 and S40.

[0067] [Aspects] The above-described exemplary embodiments will be understood by those skilled in the art to be specific examples of the following aspects.

[0068] (Section 1) An analysis system according to one embodiment comprises an X-ray source for irradiating a sample with X-rays, an energy spectrometer for spatially separating electrons according to the kinetic energy of electrons emitted from the sample, a detector for detecting the count number of electrons that have passed through the energy spectrometer, and a controller configured to generate an energy spectrum relating to the sample based on the detection result of the detector, wherein the detector is configured to detect the count number of electrons for each of a plurality of channels corresponding to each of a plurality of energy bands, and the controller is configured to calculate a correction value by performing a first correction using a first dead time corresponding to all of the plurality of channels and a second correction using a second dead time corresponding to each of the plurality of channels for the count number of each of the plurality of channels, and to generate the energy spectrum based on the correction value for each of the plurality of channels.

[0069] According to the analysis system described in paragraph 1, a technique is provided to improve the accuracy of dead time correction in an analysis system that utilizes a delay line detector.

[0070] (Section 2) In the analysis system described in Section 1, the first correction may include calculating the product of the count of each of the plurality of channels and the ratio of the incident count rate to the output count rate of the plurality of channels.

[0071] According to the analysis system described in paragraph 2, the count for each channel can be appropriately corrected according to the dead time common to all channels of the detector.

[0072] (Clause 3) In the analysis system described in paragraph 1 or 2, the second correction may be performed on the intermediate value obtained by the first correction.

[0073] According to the analysis system described in Section 3, the count for each channel can be appropriately corrected according to a correction value common to all channels of the detector and a correction value applied only to each channel.

[0074] (Clause 4) In the analysis system described in paragraph 1 or 2, the detector includes a delay line detector, and the second correction may include determining the incident count rate of each of the plurality of channels using the intermediate value obtained by the first correction, and deriving the correction value as the product of the incident count rate of each of the plurality of channels and the time required to acquire the histogram.

[0075] According to the analysis system described in Section 4, the count for each channel can be appropriately corrected according to a correction value common to all channels of the detector and a correction value applied only to each channel.

[0076] (Clause 5) A spectrum generation method according to one embodiment is a method for generating an energy spectrum relating to a sample based on the detection result of a count detector of electrons emitted from a sample irradiated with X-rays and passing through an energy spectrometer, wherein the detector is configured to detect the count number of electrons for each of a plurality of channels corresponding to each of a plurality of energy bands, and the method may include the steps of: performing a first correction corresponding to all of the plurality of channels for each of the count numbers of the plurality of channels; calculating a correction value for each of the plurality of channels by performing a second correction using a second dead time for each of the plurality of channels; and generating the energy spectrum based on the correction value for each of the plurality of channels.

[0077] According to the spectrum generation method described in Section 5, a technique is provided to improve the accuracy of dead time correction when generating an energy spectrum using detection results in an analysis system that utilizes a delay line detector.

[0078] (Clause 6) In a spectrum generation method according to Clause 5, the first correction may include calculating the product of the count number of each of the plurality of channels and the ratio of the incident count rate to the output count rate of the plurality of channels.

[0079] According to the spectrum generation method described in Section 6, the count of each channel can be appropriately corrected according to the dead time common to all channels of the detector.

[0080] (Clause 7) In the spectrum generation method described in paragraph 5 or 6, the second correction may use the intermediate value obtained by the first correction as the count number for each of the plurality of channels.

[0081] According to the spectrum generation method described in Section 7, the count for each channel can be appropriately corrected according to the dead time common to all channels of the detector and the dead time applicable only to each channel.

[0082] (Clause 8) In the spectrum generation method described in Clause 5 or 6, the detector includes a delay line detector, and in the second correction, the intermediate value obtained by the first correction is used as the count number for each of the plurality of channels, and the second correction may include determining the incident count rate for each of the plurality of channels using the intermediate value obtained by the first correction, and deriving the product of the incident count rate for each of the plurality of channels and the time required to acquire the histogram as the correction value.

[0083] According to the spectrum generation method described in Section 8, the count for each channel can be appropriately corrected according to a dead time calculation common to all channels of the detector and a dead time calculation applied only to each channel.

[0084] (Clause 9) A signal processing device according to one embodiment is a signal processing device for a charged particle detector including a microchannel plate (MCP) and a delay line detector (DLD), which is configured to generate a histogram that counts events for each arrival time difference of electrical pulses output from both ends of the conductor of the delay line detector, and is configured to perform a two-stage dead time correction using a first dead time obtained from the total count of the histogram and a second dead time obtained from the count for each channel of the histogram.

[0085] The signal processing device described in paragraph 9 provides a technique for improving the accuracy of dead time correction in an analysis system that utilizes a delay line detector.

[0086] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope of the claims are intended to be included. Furthermore, each technique in the embodiments is intended to be practiced individually or, as far as possible, in combination with other techniques in the embodiments.

[0087] 10 X-ray source, 40 energy spectrometer, 50 detector, 51 MCP, 52 DLD, 52A, 52B terminals, 52X collector wire, 52Y reference wire, 52Z holder, 60 processing unit, 80, 90 arrows, 81, 82, 91, 92 figures, 100 XPS.

Claims

1. An analytical system comprising: an X-ray source for irradiating a sample with X-rays; an energy spectrometer for spatially separating electrons according to the kinetic energy of electrons emitted from the sample; a detector for detecting the count number of electrons that have passed through the energy spectrometer; and a processing device configured to generate an energy spectrum relating to the sample based on the detection results of the detector, wherein the detector is configured to detect the count number of electrons for each of a plurality of channels corresponding to each of a plurality of energy bands; the processing device is configured to calculate a correction value by performing a first correction using a first dead time corresponding to all of the plurality of channels and a second correction using a second dead time corresponding to each of the plurality of channels for the count number of each of the plurality of channels; and generates the energy spectrum based on the correction value for each of the plurality of channels.

2. The analysis system according to claim 1, wherein the first correction includes calculating the product of the count of each of the plurality of channels and the ratio of the incident count rate to the output count rate of the plurality of channels.

3. The analysis system according to claim 1, wherein the second correction is performed on the intermediate value obtained by the first correction.

4. The analysis system according to claim 1, wherein the detector includes a delay line detector, and the second correction includes determining the incident count rate of each of the plurality of channels using the intermediate value obtained by the first correction, and deriving the product of the incident count rate of each of the plurality of channels and the time required to acquire the histogram as the correction value.

5. A method for generating an energy spectrum relating to a sample irradiated with X-rays, based on the detection result of electrons emitted from the sample and passing through an energy spectrometer by a count detector, wherein the detector is configured to detect the electron count for each of a plurality of channels corresponding to each of a plurality of energy bands; the method comprises the steps of: performing a first correction corresponding to all of the plurality of channels for each of the counts of the plurality of channels; calculating a correction value for each of the plurality of channels by performing a second correction corresponding to each of the plurality of channels for each of the plurality of channels; and generating the energy spectrum based on the correction value for each of the plurality of channels.

6. The spectrum generation method according to claim 5, wherein the first correction includes calculating the product of the count number of each of the plurality of channels and the ratio of the incident count rate to the output count rate of the plurality of channels.

7. The spectrum generation method according to claim 5, wherein in the second correction, the intermediate value obtained by the first correction is used as the count number for each of the plurality of channels.

8. The spectral generation method according to claim 5, wherein the detector includes a delay line detector, the second correction uses the intermediate value obtained by the first correction as the count for each of the plurality of channels, the second correction includes determining the incident count rate for each of the plurality of channels using the intermediate value obtained by the first correction, and deriving the product of the incident count rate for each of the plurality of channels and the time required to acquire the histogram as the correction value.

9. A signal processing device for a charged particle detector including a microchannel plate (MCP) and a delay line detector (DLD), wherein the signal processing device is configured to generate a histogram that counts events for each arrival time difference of electrical pulses output from both ends of the conductor of the delay line detector, and is configured to perform a two-stage dead time correction using a first dead time obtained from the total count of the histogram and a second dead time obtained from the count for each channel of the histogram.

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