Time-of-flight secondary ion mass spectrometer and mass spectrometry method thereof

Abstract

The application relates to the field of component analysis, and particularly discloses a time-of-flight secondary ion mass spectrometer and a mass spectrometry method thereof, which comprises the following steps: S1: determining the components of a sample to be measured according to secondary ions generated on the surface of the sample to be measured in a scanning mode; S2: focusing the components on a grating to obtain a first component distribution diagram; S3: judging whether a target region with uniform color distribution exists in the first component distribution diagram; S4: if the target region exists in the first component distribution diagram, scanning the target region in a sputtering mode, and performing mass spectrometry on the sample to be measured; and S5: if the target region does not exist in the first component distribution diagram, replacing the scanning region on the surface of the sample to be measured, and executing the step S1. According to the mass spectrometry method, the surface of the sample to be measured is scanned in the scanning mode before sputtering scanning is performed on the sample to be measured, the sputtering scanning is performed according to the position determined through imaging, and the accuracy of mass spectrometry is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of component analysis, and in particular to a time-of-flight secondary ion mass spectrometer and a mass spectrometry method thereof. BACKGROUND

[0002] Secondary ion mass spectrometry is a nearly non-destructive surface analysis technique that can obtain isotopic and component information of a surface of a measured substance, has high analysis sensitivity, small signal background noise, does not require chemical treatment of a sample, can directly analyze a solid sample, and is widely used in the fields of analytical chemistry, environmental science, life science, and earth science. Secondary ion mass spectrometry can obtain accurate chemical element composition information in a very small range (a few microns) on a sample target, and can be used for surface element analysis of various samples. Secondary ion mass spectrometry analysis techniques are divided into static secondary ion mass spectrometry analysis and dynamic secondary ion mass spectrometry analysis. Static secondary ion mass spectrometry analysis uses low ion flow density (less than 10 -7 A / cm 2 ) and low energy (a few hundred to a few thousand eV) primary ion bombardment of a surface to perform mass spectrometry analysis on the outgoing secondary ions.

[0003] Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis is a static mass spectrometry method that combines secondary ion mass spectrometry technology and time-of-flight mass analysis technology. The technology measures the mass of ions by measuring the time taken by secondary ions of different masses to reach a detector after the secondary ions are excited from a sample surface by primary ions. The technology can analyze layers one by one without damaging the sample surface, and can achieve depth analysis of the sample. Compared with other surface depth analysis methods, time-of-flight secondary ion mass spectrometry analysis has high analysis sensitivity, high signal-to-noise ratio, and high depth resolution. In the current time-of-flight secondary ion mass spectrometry analysis, a sputtering ion gun is directly turned on, and the sample surface is scanned in a sputtering mode to determine the elements and content of the sample based on the data obtained by the scanning. However, the existing time-of-flight secondary ion mass spectrometry analysis method ignores the non-uniformity of the sample surface, which leads to a large error in the measurement results when the sample surface is not uniform.

[0004] Therefore, how to solve the above technical problems should be the focus of those skilled in the art. SUMMARY

[0005] The purpose of the present application is to provide a time-of-flight secondary ion mass spectrometer and a mass spectrometry method thereof to improve the accuracy of mass spectrometry detection.

[0006] To solve the above technical problems, the application provides a time-of-flight secondary ion mass spectrometry method, comprising:

[0007] Step S1: determining the composition of the sample to be measured according to the secondary ions generated on the surface of the sample to be measured in a scanning mode;

[0008] Step S2: focusing the composition on a grating to obtain a first composition distribution map;

[0009] Step S3: determining whether a target region with uniform color distribution exists in the first composition distribution map;

[0010] Step S4: if the target region exists in the first composition distribution map, scanning the target region in a sputtering mode and performing mass spectrometry analysis on the sample to be measured;

[0011] Step S5: if the target region does not exist in the first composition distribution map, replacing the scanning region on the surface of the sample to be measured and performing step S1.

[0012] Optionally, scanning the target region in the sputtering mode and performing mass spectrometry analysis on the sample to be measured comprises:

[0013] In the sputtering mode, the target region is scanned by using a first ion beam to obtain a mass spectrum corresponding to the target region;

[0014] The composition and composition content of the sample to be measured are determined according to the mass spectrum.

[0015] Optionally, when the number of target regions is two or more, determining the composition content of the sample to be measured according to the mass spectrum comprises:

[0016] The composition content of the sample to be measured is determined according to the mass spectrum corresponding to each target region;

[0017] The average value of all the composition contents to be determined is determined as the composition content of the sample to be measured.

[0018] Optionally, the method further comprises:

[0019] Obtaining the spectral peak intensity of each composition per second of scanning;

[0020] Determining the content-depth distribution relationship of each composition in the sample to be measured according to the spectral peak intensity.

[0021] Optionally, the method further comprises:

[0022] Focusing the composition on a grating to obtain a second composition distribution map;

[0023] Verifying the uniformity of the surface of the sample to be measured according to the second composition distribution map.

[0024] Optionally, in the scanning mode, determining the composition of the sample to be tested according to the secondary ions generated from the surface of the sample to be tested comprises:

[0025] In the scanning mode, the surface of the sample to be tested is scanned by the second ion beam to generate secondary ions from the surface of the sample to be tested;

[0026] The mass-to-charge ratio of the secondary ions is determined according to the time of flight of the secondary ions;

[0027] The composition of the sample to be tested is determined according to the mass-to-charge ratio.

[0028] Optionally, scanning the surface of the sample to be tested by the second ion beam comprises:

[0029] The surface of the sample to be tested is scanned by the Bi + ion beam, and the scanning time is 30s-120s.

[0030] Optionally, scanning the target region by the first ion beam comprises:

[0031] The target region is scanned by the O2 + ion beam, and the energy of the O2 + ion beam is 1keV-3keV, the incident angle of the O2 + ion beam is 20°-70°, and the scanning time is 30min-120min.

[0032] Optionally, in the scanning mode, before determining the composition of the sample to be tested according to the secondary ions generated from the surface of the sample to be tested, the method further comprises:

[0033] Neutralizing the electric charge on the surface of the sample to be tested.

[0034] The application also provides a time-of-flight secondary ion mass spectrometer for performing any one of the time-of-flight secondary ion mass spectrometry methods described above.

[0035] The time-of-flight secondary ion mass spectrometry method provided in the application comprises the following steps: S1, determining the composition of a sample to be measured according to secondary ions generated on the surface of the sample to be measured in a scanning mode; S2, focusing the composition on a grating to obtain a first composition distribution map; S3, judging whether a target region with uniform color distribution exists in the first composition distribution map; S4, if the target region exists in the first composition distribution map, scanning the target region in a sputtering mode and performing mass spectrometry analysis on the sample to be measured; and S5, if the target region does not exist in the first composition distribution map, replacing the scanning region on the surface of the sample to be measured and performing step S1.

[0036] It can be seen that, in the mass spectrometry method in the application, before sputtering scanning is performed on the sample to be measured, the surface of the sample to be measured is scanned in a scanning mode, the composition of the sample to be measured is determined according to secondary ions generated on the surface of the sample to be measured, a first composition distribution map is obtained according to the composition, and it is judged whether a target region with uniform color distribution exists in the first composition distribution map. The region with uniform color distribution indicates that the composition distribution of the region is uniform, and then mass spectrometry analysis is performed on the target region with uniform composition distribution. If the target region with uniform color distribution does not exist, the scanning region is replaced, the target region is determined again, and mass spectrometry analysis is performed again, so that the accuracy of mass spectrometry analysis is improved.

[0037] In addition, the application also provides a time-of-flight secondary ion mass spectrometer with the above advantages. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0039] Figure 1 A flowchart of a time-of-flight secondary ion mass spectrometry method provided by an embodiment of the application;

[0040] Figure 2 A flowchart of another time-of-flight secondary ion mass spectrometry method provided by an embodiment of the application;

[0041] Figure 3 A flowchart of another time-of-flight secondary ion mass spectrometry method provided by an embodiment of the application;

[0042] Figure 4 A flowchart of another time-of-flight secondary ion mass spectrometry method provided by an embodiment of the application;

[0043] Figure 5 A flowchart of another time-of-flight secondary ion mass spectrometry analysis method provided in the embodiments of this application;

[0044] Figure 6 A flowchart of another time-of-flight secondary ion mass spectrometry analysis method provided in the embodiments of this application;

[0045] Figure 7 This is a spectrum of iron elements in the stainless steel metal plate according to an embodiment of this application;

[0046] Figure 8 This is a spectrum of chromium in a stainless steel metal plate according to an embodiment of this application;

[0047] Figure 9 This is a spectrum of nickel elements in a stainless steel metal plate according to an embodiment of this application;

[0048] Figure 10 This is a spectrum of molybdenum in a stainless steel metal plate according to an embodiment of this application;

[0049] Figure 11 For the stainless steel metal plate surface in the embodiments of this application, element Ce is shown in scanning mode. 140 Distribution map;

[0050] Figure 12 For the stainless steel metal plate surface in the embodiments of this application, element Ce is shown in scanning mode. 142 Distribution map;

[0051] Figure 13 For the stainless steel sheet surface in the sputtering mode of this application embodiment, element Ce is... 140 Distribution map;

[0052] Figure 14 For the stainless steel sheet surface in the sputtering mode of this application embodiment, element Ce is... 142 Distribution map;

[0053] Figure 15 This is a depth distribution of the content of each element in the stainless steel metal plate of the embodiments of this application;

[0054] Figure 16 This is a schematic diagram of the structure of a time-of-flight secondary ion mass spectrometer provided in an embodiment of this application. Detailed Implementation

[0055] For those skilled in the art, the application will be further described in detail below with the drawings and specific embodiments. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the application.

[0056] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced without the specific details, other than those described herein, and it is understood that the present application is not limited to the embodiments described herein and can be practiced with or without other embodiments.

[0057] As described in the background section, at present, when carrying out time-of-flight secondary ion mass spectrometry, a sputtering ion gun is directly turned on, the surface of the sample is scanned in sputtering mode, and the elements and content of the sample are determined according to the data obtained by scanning. However, the existing time-of-flight secondary ion mass spectrometry method ignores the problem of non-uniformity of the sample surface during analysis, which leads to a large error in the measurement result when the sample surface is not uniform.

[0058] Therefore, the present application provides a time-of-flight secondary ion mass spectrometry method, please refer to Figure 1 The method comprises:

[0059] Step S1: In the scanning mode, the composition of the sample to be measured is determined according to the secondary ions generated by the surface of the sample to be measured.

[0060] Before scanning, the sample to be measured needs to be prepared first, and the sample to be measured must be kept stable under the ultra-high pressure condition (pressure <10 8 Torr) in the SIMS analysis chamber. For various reasons, SIMS analysis must be performed under ultra-high pressure conditions. To ensure that incident particles and secondary ions (secondary ions) propagate from their point of origin to their final destination without colliding with other atoms, molecules or ions; The composition and structure of the sample must remain constant during analysis. Ultra-high pressure conditions are particularly important to prevent contamination of the sample during SIMS analysis, as SIMS is surface-specific and can detect substances with concentrations in the ppm to ppb range.

[0061] The form of the sample under test includes, but is not limited to, pressed powder, bulk film, fiber, particle and film spin-coated on a substrate (e.g. glass, aluminum foil, silver, etc.). The sample under test is fixed on a sample stub by mechanical means or with double-sided adhesive tape. The thickness and morphology of the sample under test will affect the possibility of generating secondary ions, and thus affect the stability of the SIMS spectrum. The cleanliness of the surface of the sample under test is also an important consideration in sample preparation, because any contaminants deposited on the surface during handling or processing will affect the accuracy of the analysis. In addition, the sample under test should be analyzed immediately after preparation to avoid surface diffusion, molecular reorientation or contamination of the surface of the sample under test by the laboratory environment.

[0062] As an implementation manner, in the scanning mode, determining the composition of the sample under test according to the secondary ions generated from the surface of the sample under test includes:

[0063] Step S11: in the scanning mode, the surface of the sample under test is scanned by using the second ion beam to make the surface of the sample under test generate secondary ions.

[0064] Optionally, scanning the surface of the sample under test by using the second ion beam includes: using Bi + The ion beam scans the surface of the sample under test, and the scanning time is 30s-120s. However, the present application does not limit this, and other types of ion beams can also be selected for scanning. The dose of the ion beam and the scanning time are determined according to the specific situation. Bi + The dose of the ion beam is selected to be a smaller value according to the instrument used

[0065] Step S12: determining the mass-to-charge ratio of the secondary ions according to the time of flight of the secondary ions.

[0066] Step S13: determining the composition of the sample under test according to the mass-to-charge ratio.

[0067] Each mass-to-charge ratio corresponds to a composition. When one mass-to-charge ratio corresponds to multiple compositions, the specific type of the sample under test can be combined to determine which composition in the sample under test is.

[0068] The steps S11 to S13 will be described below.

[0069] The ions in the second ion beam are incident on the surface of the sample under test, so that the sample under test generates secondary ions, which enter the TOF analyzer and are finally detected. The TOF analyzer separates the secondary ions according to the mass-to-charge ratio m / z (mass / charge). The mass m of the ions is determined according to the time they take to accelerate to a common energy E in an extraction field and pass through the length L of the field-free flight tube. The relationship between the common energy E and the flight time t is:

[0070] E = mv2 / 2 = mL 2 / 2zt 2 (1)

[0071] where v is the velocity of the secondary ions, m is the mass of the ions, t is the time of flight, E is the acceleration energy of the secondary ions, and L is the length of the field-free flight tube, i.e. the flight distance of the secondary ions.

[0072] The time of flight t is proportional to the square root of the mass m of the exiting secondary ions, i.e.

[0073] t = L(m / 2zE) 1 / 2 (2)

[0074] Therefore, under the condition of the same energy, the ion with smaller mass flies faster and is detected earlier than the ion with larger mass.

[0075] When the ion energy is constant, the best ion separation or mass resolution can be obtained. The primary ion source must produce secondary ions with minimum time dispersion and thus minimum energy dispersion using short pulse width (sub-nanoseconds). Then a fixed voltage accelerates the secondary ions into the TOF analyzer, the polarity of which determines whether positive or negative secondary ions are analyzed. The energy and angular dispersion of the secondary ions produced during the emission process can be compensated by focusing elements such as ion mirrors or mirrors. For example, mirrors focus the secondary ions through a decelerating electric field in the middle of the flight path, thereby improving the mass separation (higher mass resolution).

[0076] After the secondary ions are separated in the TOF analyzer, they are focused onto the detector by ion lenses. Since high-mass ions propagate at a slower speed, a post-acceleration voltage of up to 15 keV is applied to the ions to improve the detection efficiency. The ion impact detection unit usually consists of a photoelectric conversion electrode, a channel plate, a scintillator, a photomultiplier tube, and a counter in series.

[0077] Further, the mass spectrum can also be determined according to the mass-to-charge ratio and the electrical signal intensity of the secondary ions.

[0078] Step S2: focusing the components onto the grating to obtain a first component distribution map.

[0079] The first component distribution map is a picture with color.

[0080] The chemical components of the sample to be tested can be drawn by focusing the primary light beam to a narrow diameter and grating on the surface. A complete mass spectrum includes each point of the ion beam grating, and this mode is called microprobe imaging. Liquid metal ion guns (for example, Ga +The primary beam can be focused to 150 nanometers, allowing images to be generated with the same lateral resolution. Measurements can take from a few minutes to several hours. Smaller beam diameters reduce the amount of material available per pixel (image point) in the uppermost monolayer. This limits the number of secondary ions that can be generated and reduces the sensitivity and dynamic range per point. After data acquisition, specific ions or combinations of ions can be selected and their surface distribution plotted. Similarly using SIMS imaging, regions of interest can be identified from the total ion image and the mass spectra of the pixels within that region summed, allowing spectral evaluation with restored sensitivity and dynamic range. To generate a topographic map of the surface, ion-induced secondary electrons (similar to a scanning electron microscope) or total secondary ion emission can be used.

[0081] Step S3: judging whether there is a target region with uniform color distribution in the first component distribution map.

[0082] The presence or absence of a target region can be determined by observing the first component distribution map.

[0083] Step S4: if the target region exists in the first component distribution map, scanning the target region in sputtering mode and performing mass spectrum analysis on the sample to be tested.

[0084] Step S5: if the target region does not exist in the first component distribution map, changing the scanning area on the surface of the sample to be tested and performing step S1.

[0085] The mass spectrum analysis method in the present application first scans the surface of the sample to be tested in scanning mode before sputtering scanning, determines the components of the sample to be tested according to the secondary ions generated by the surface of the sample to be tested, obtains a first component distribution map according to the components, and then judges whether there is a target region with uniform color distribution in the first component distribution map. The region with uniform color distribution indicates that the component distribution of this part of the region is uniform, and then the target region with uniform component distribution is subjected to mass spectrum analysis. If there is no target region with uniform color distribution, the scanning area is changed, the target region is determined again, and mass spectrum analysis is performed again, avoiding accidental errors caused by unevenness of the surface of the sample to be tested, thereby improving the accuracy of mass spectrum analysis.

[0086] Please refer to Figure 2 On the basis of the above embodiment, in an embodiment of the present application, the time-of-flight secondary ion mass spectrum analysis method comprises:

[0087] Step S1: determining the components of the sample to be tested according to the secondary ions generated by the surface of the sample to be tested in scanning mode.

[0088] Step S2: focusing the components onto a grating to obtain a first component distribution map.

[0089] Step S3: judging whether there is a target region with uniform color distribution in the first component distribution map.

[0090] Step S4: if there is the target region in the first component distribution map, scanning the target region by using the first ion beam in sputtering mode to obtain a mass spectrum corresponding to the target region.

[0091] As an implementable manner, scanning the target region by using the first ion beam includes:

[0092] using O2 + scanning the target region by using the ion beam, wherein the O2 + the energy of the ion beam is between 1 keV and 3 keV, the O2 + the incident angle of the ion beam is between 20° and 70°, and the scanning time is between 30 min and 120 min.

[0093] Step S5: determining the component and component content of the sample to be tested according to the mass spectrum.

[0094] The abscissa of the mass spectrum is the mass-to-charge ratio, and the ordinate is the intensity. The mass spectrum contains a large number of peaks, and the component of the sample to be tested can be determined according to the mass-to-charge ratio, and the component content is determined according to the peak area. By evaluating the quality of the signal, peaks can usually be identified from the molecular ion of the analyte, fragments of the molecular ion, and ions of any other components that may exist in the sample.

[0095] The method for evaluating TOF-SIMS signals is similar to conventional mass spectrometry. One method is to compare the mass spectrum of the sample to be tested with the fingerprint spectrum of the standard by using a spectral library and manual. In addition, the latest software version attached to the TOF-SIMS mass spectrometer contains a database with a searchable spectral library. The operator can add other standard spectra. Another method for TOF-SIMS spectrum evaluation is logical deduction. The molecular structure can usually be identified by the knowledge of fragmentation patterns and fragmentation pathways. The fragmentation rules suitable for electron impact mass spectrometry (alpha and beta cleavage, rearrangement processes) are useful in elucidating fragmentation processes; TOF-SIMS software containing a database that allows "peak identification" is also useful; consider the accurate mass of the peak of interest, and generate a list of possible ion information.

[0096] Step S6: if there is no target region in the first component distribution map, replacing the scanning region on the surface of the sample to be tested, and performing step S1.

[0097] In the mass spectrum analysis, a target region on the surface of the sample to be measured can be directly sputtered and scanned to determine the composition and content of the sample to be measured. In an embodiment of the present application, in order to improve the accuracy of the measurement, a plurality of target regions on the surface of the sample to be measured can be measured. When the number of target regions is two or more, refer to Figure 3 , the time-of-flight secondary ion mass spectrum analysis method comprises:

[0098] Step S1: in the scanning mode, the composition of the sample to be measured is determined according to the secondary ions generated on the surface of the sample to be measured.

[0099] Step S2: focus the composition on the grating to obtain a first composition distribution map.

[0100] Step S3: determine whether there is a target region with uniform color distribution in the first composition distribution map.

[0101] Step S4: if the target region exists in the first composition distribution map, in the sputtering mode, the target region is scanned by using the first ion beam to obtain a mass spectrum corresponding to the target region.

[0102] Step S5: determine the content of the to-be-determined composition of the sample to be measured according to the mass spectrum corresponding to each target region.

[0103] Step S6: determine the average value of all to-be-determined composition contents as the composition content of the sample to be measured.

[0104] Step S7: if the target region does not exist in the first composition distribution map, replace the scanning region on the surface of the sample to be measured, and execute step S1.

[0105] On the basis of the above embodiment, in an embodiment of the present application, refer to Figure 4 , the time-of-flight secondary ion mass spectrum analysis method comprises:

[0106] Step S1: in the scanning mode, the composition of the sample to be measured is determined according to the secondary ions generated on the surface of the sample to be measured.

[0107] Step S2: focus the composition on the grating to obtain a first composition distribution map.

[0108] Step S3: determine whether there is a target region with uniform color distribution in the first composition distribution map.

[0109] Step S4: if the target region exists in the first composition distribution map, in the sputtering mode, the target region is scanned by using the first ion beam to obtain a mass spectrum corresponding to the target region.

[0110] Step S5: determining the components and component contents of the sample to be tested according to the mass spectrum.

[0111] Step S6: obtaining the spectral peak intensity of each component at each second of scanning.

[0112] Step S7: determining the content-depth distribution relationship of each component in the sample to be tested according to the spectral peak intensity.

[0113] Step S8: if the target region does not exist in the first component distribution map, changing the scanning region of the surface of the sample to be tested, and performing step S1.

[0114] The ion mass spectrum analysis method in the embodiment can obtain the content-depth distribution relationship of each component in the sample to be tested, that is, realize the depth analysis of the sample to be tested.

[0115] On the basis of the above embodiment, in an embodiment of the present application, please refer to Figure 5 , the time-of-flight secondary ion mass spectrum analysis method comprises:

[0116] Step S1: determining the components of the sample to be tested according to the secondary ions generated on the surface of the sample to be tested in the scanning mode.

[0117] Step S2: focusing the components onto the grating to obtain a first component distribution map.

[0118] Step S3: judging whether a target region with uniform color distribution exists in the first component distribution map.

[0119] Step S4: if the target region does not exist in the first component distribution map, changing the scanning region of the surface of the sample to be tested, and performing step S1.

[0120] Step S5: if the target region exists in the first component distribution map, scanning the target region by using a first ion beam in the sputtering mode to obtain a mass spectrum corresponding to the target region.

[0121] Step S6: determining the components and component contents of the sample to be tested according to the mass spectrum.

[0122] Step S7: obtaining the spectral peak intensity of each component at each second of scanning.

[0123] Step S8: determining the content-depth distribution relationship of each component in the sample to be tested according to the spectral peak intensity.

[0124] Step S9: focusing the components onto the grating to obtain a second component distribution map.

[0125] It can be understood that the components in this step are the components scanned in the sputtering mode.

[0126] Step S10: judging the uniformity of the surface of the sample to be measured according to the second component distribution map.

[0127] The uniformity of the surface of the sample to be measured is judged according to the color distribution of the second component distribution map.

[0128] In the embodiment, the component and the component content of the sample to be measured can be analyzed to obtain the second component distribution map of the sample to be measured, so that the horizontal analysis of the sample to be measured can be realized, and the vertical analysis of the sample to be measured can also be realized.

[0129] For reference Figure 6 On the basis of the above embodiment, in an embodiment of the present application, the time-of-flight secondary ion mass spectrometry method comprises:

[0130] Step S1: neutralizing the charge on the surface of the sample to be measured.

[0131] The charge on the surface of the sample to be measured can be neutralized by the electrons emitted by the electron gun.

[0132] Most of the samples to be measured of biological materials are electrical insulators, and electric charges will accumulate on the surface during the analysis process. This charge accumulation can reduce or completely eliminate the secondary ion signal. The sample to be measured will be charged during the sputtering process, because the positively charged primary ions bombard the surface of the sample to be measured and lose secondary electrons at the same time. Unless the sample to be measured has sufficient electrical conductivity to transmit electrons to the sputtering area, the area will obtain a net positive charge. In order to neutralize the charge accumulation during the TOF-SIMS analysis process, a low-energy electron pulse is applied between the primary ion pulses on the surface of the sample to be measured. The current and voltage of the electrons must be low enough to minimize the ion emission stimulated by the electrons and the damage to the sample to be measured.

[0133] The collection rate of secondary ions depends on several factors and is not directly proportional to the concentration of components in the sample to be measured, resulting in certain difficulties in the quantitative analysis of TOF-SIMS. The "matrix effect" plays an important role in the quantitative analysis of TOF-SIMS, and the problem can be defined as the change of ion yield with the change of surface components. In different chemical environments, the same analyte will not have the same secondary ion yield, so it is difficult to make direct comparisons between samples. During the analysis, the environment of a single sample to be measured will also change. As a result, preferential sputtering will cause different degrees of removal of particles from the sample to be measured. In addition, due to the change of the sputtering process, the possibility of ion formation can change.

[0134] Step S2: determining the component of the sample to be measured according to the secondary ions generated on the surface of the sample to be measured in the scanning mode.

[0135] Step S3: focusing the components on the grating to obtain a first component distribution map.

[0136] Step S4: judging whether a target region with uniform color distribution exists in the first component distribution map.

[0137] Step S5: if the target region does not exist in the first component distribution map, changing the scanning region on the surface of the sample to be tested and performing step S1.

[0138] Step S6: if the target region exists in the first component distribution map, scanning the target region by using a first ion beam in a sputtering mode to obtain a mass spectrum corresponding to the target region.

[0139] Step S7: determining the components and component contents of the sample to be tested according to the mass spectrum.

[0140] Step S8: obtaining the spectral peak intensity of each component at each second of scanning.

[0141] Step S9: determining the content and depth distribution relationship of each component in the sample to be tested according to the spectral peak intensity.

[0142] Step S10: focusing the components on the grating to obtain a second component distribution map.

[0143] It can be understood that the components in this step are components scanned in the sputtering mode.

[0144] Step S11: verifying the uniformity of the surface of the sample to be tested according to the second component distribution map.

[0145] In this embodiment, the charge of the surface of the sample to be tested is neutralized before the sample to be tested is scanned, so that the electric signal intensity of the secondary ions measured can be enhanced.

[0146] The time-of-flight secondary ion mass spectrometry method in the present application is described below by taking the accurate analysis of the element contents of a processed 316L stainless steel sheet sample as an example, in which the cerium element is artificially added and is of great concern.

[0147] Step 1, sample preparation: each region of the stainless steel sheet is cut into a plurality of 2cm x 2cm square thin plates using a wire cutting machine, labeled and sorted, cleaned with a dust-free cloth before measurement, and the stainless steel sheet is pasted on the secondary ion mass spectrometer workbench using copper glue.

[0148] Step 2, turn on the time-of-flight secondary ion mass spectrometer: including cleaning the vacuum, vacuumizing, opening the air valve, etc.

[0149] Step 3, turn on the electron gun to neutralize the surface charge of the sample to be tested, and enhance the intensity of the electrical signal obtained by measurement.

[0150] Step 4, in the surface scanning mode of the time-of-flight secondary ion mass spectrometer, select the primary ion beam Bi + Scan the stainless steel plate at a low dose, and the scanning sampling time is 60 seconds. The secondary ions generated by the stainless steel plate enter the time-of-flight analyzer, and the spectral peak diagrams of iron (Fe), chromium (Cr), nickel (Ni), and molybdenum (Mo) at this position are calculated, as shown in Figure 7 、 Figure 8 、 Figure 9 、 Figure 10

[0151] Step 5, according to the mass-to-charge ratio and the information of the stainless steel grade, the composition and content of each element can be determined, and it can be determined that the main elements include iron (Fe), chromium (Cr), nickel (Ni), molybdenum (Mo), and cerium (Ce). The chemical composition of the stainless steel plate can be imaged on the grating to obtain the composition distribution diagrams of Ce 140 and Ce 142 , as shown in Figure 11 and Figure 12 . According to the color distribution of the two-dimensional composition distribution diagram, a uniform region is selected as the target region, and step 6 is entered. If a uniform region cannot be found, the sample detection position is changed, and step 4 is returned.

[0152] As can be seen from Figure 11 and Figure 12 , the color uniformity of each region in Figure 11 and Figure 12 is different, indicating that the overall uniformity of the scanned region is poor at this time, and a region with uniform color needs to be found in Figure 11 and Figure 12 as the target region, and the composition distribution uniformity of the target region is good.

[0153] Step 6, turn on the sputtering ion gun to generate O2 + ion beam at an energy of 2 keV and an incident angle of 45 degrees. The instrument analysis mode uses the sputtering mode, the sputtering area is 350 μm x 350 μm, but only the data of the center region with an area of 100 μm x 100 μm is collected, the sampling time is 60 minutes, and the secondary ions generated enter the time-of-flight analyzer to calculate the spectral peak diagram at this position.

[0154] Step 7, according to the obtained spectral peak diagram again, the composition and content of each element are determined, and the composition distribution diagram is imaged again, the composition distribution diagrams of Ce 140 and Ce 142 are as shown in Figure 13 and Figure 14 ​The uniformity of the position is analyzed as shown. Figure 13 It can be seen that the color distribution of the overall area is uniform, Figure 14 The color distribution of the overall area in the middle is also relatively uniform, further proving that the color distribution of the selected target area is uniform.

[0155] Step 8, in sputtering mode, the spectral peak information obtained by scanning per second is summarized and extracted and arranged in the same coordinate to obtain the content-depth distribution of each element of the stainless steel metal plate, as shown in Figure 15 .

[0156] Step 9, turn off the time-of-flight secondary ion mass spectrometer: first stop the software running, stop each ion gun, close the air valve, and wait for the vacuum degree to decrease to near atmospheric pressure before removing the stainless steel metal plate sample;

[0157] The time-of-flight secondary ion mass spectrometer working parameters are as follows:

[0158] Primary ion beam: Bi + , energy 30keV, 45deg incident;

[0159] Scan area: 500μm×500μm;

[0160] Sputtering area: 350μm×350μm;

[0161] Analysis area: 100μm×100μm;

[0162] Secondary ion polarity and mass range: negative ion, 0-900amu;

[0163] Sputtering ion beam: O2 + , energy 2keV, 45deg incident.

[0164] The application also provides a time-of-flight secondary ion mass spectrometer for performing the time-of-flight secondary ion mass spectrometry method described in any of the above embodiments.

[0165] The structure diagram of the time-of-flight secondary ion mass spectrometer is shown in Figure 16 , including an ion source 1 for emitting an ion beam, a primary ion optical system 2, and a time-of-flight analyzer 3.

[0166] The time-of-flight secondary ion mass spectrometer in the application, when performing mass spectrum analysis, first scans the surface of the sample to be measured in a scanning mode before sputtering scanning is performed on the sample to be measured, determines the composition of the sample to be measured according to secondary ions generated on the surface of the sample to be measured, obtains a first composition distribution map according to the composition, and further judges whether a target region with uniform color distribution exists in the first composition distribution map. The region with uniform color distribution indicates that the composition distribution of the region is uniform, and then mass spectrum analysis is performed on the target region with uniform composition distribution. If no target region with uniform color distribution exists, the scanning region is replaced, the target region is determined again, and mass spectrum analysis is performed again, so as to improve the accuracy of mass spectrum analysis.

[0167] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0168] The time-of-flight secondary ion mass spectrometer and the mass spectrum analysis method thereof provided in the application are described in detail above. The principles and implementation manners of the application are described by applying specific examples in the text. The description of the above embodiments is only used to help understand the method and the core idea of the application. It should be pointed out that, for ordinary skilled in the art, some improvements and modifications can be made to the application without departing from the principles of the application. These improvements and modifications also fall within the protection scope of the claims of the application.

Claims

1. A time-of-flight secondary ion mass spectrometry method, characterized by, The method comprises the following steps: S1. In a scanning mode, determining the composition of the sample to be tested according to secondary ions generated on the surface of the sample to be tested; S2. Focusing the composition onto a grating to obtain a first composition distribution map; the first composition distribution map is a picture with color; S3. Judging whether a target region with uniform color distribution exists in the first composition distribution map; the target region with uniform color distribution indicates that the composition distribution of the region is uniform; S4. If the target region exists in the first composition distribution map, scanning the target region in a sputtering mode and performing mass spectrum analysis on the sample to be tested; S5. If the target region does not exist in the first composition distribution map, replacing the scanning region on the surface of the sample to be tested and performing step S1. Scanning the target region in a sputtering mode and performing mass spectrum analysis on the sample to be tested comprises the following steps: In the sputtering mode, the target region is scanned by the first ion beam to obtain a mass spectrum corresponding to the target region; the scanning of the target region by the first ion beam comprises: scanning the target region by the first ion beam in the O2 + The ion beam scans the target region, wherein the O2 + The energy of the ion beam is between 1 keV and 3 keV, the O2 + The incident angle of the ion beam is between 20° and 70°, and the scanning time is between 30 min and 120 min; Determining the composition and content of the sample to be tested according to the mass spectrum map; Obtaining the spectral peak intensity of each component at each second scanning time; Determining the content and depth distribution relationship of each component in the sample to be tested according to the spectral peak intensity; In the scanning mode, determining the composition of the sample to be tested according to secondary ions generated on the surface of the sample to be tested comprises the following steps: In the scanning mode, the surface of the sample to be measured is scanned by the second ion beam to generate secondary ions from the surface of the sample to be measured; and the scanning of the surface of the sample to be measured by the second ion beam comprises: scanning the surface of the sample to be measured by Bi + scanning the surface of the sample to be measured by the ion beam, wherein the scanning time is 30s-120s. Determining the mass-to-charge ratio of the secondary ions according to the time of flight of the secondary ions; Determining the composition of the sample to be tested according to the mass-to-charge ratio.

2. The time-of-flight secondary ion mass spectrometry method according to Claim 1, wherein When the number of target regions is two or more, determining the composition and content of the sample to be tested according to the mass spectrum map comprises the following steps: Determining the content of the sample to be tested according to the mass spectrum map corresponding to each target region; Determining the average value of all the content of the sample to be tested as the composition and content of the sample to be tested.

3. The time-of-flight secondary ion mass spectrometry method according to Claim 1, wherein The method further comprises the following steps: Focusing the composition onto a grating to obtain a second composition distribution map; According to the second composition distribution map, the uniformity of the surface of the sample to be tested is inspected.

4. The time-of-flight secondary ion mass spectrometry method according to any one of claims 1 to 3, characterized by, Before determining the composition of the sample to be tested according to secondary ions generated on the surface of the sample to be tested in the scanning mode, the method further comprises the following step: Neutralizing the charge on the surface of the sample to be tested.

5. A time-of-flight secondary ion mass spectrometer, characterised in that, The time-of-flight secondary ion mass spectrometer is used to perform the time-of-flight secondary ion mass spectrum analysis method according to any one of claims 1 to 4.

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