JPH0419954A - Secondary ion mass spectrometry - Google Patents

Abstract

PURPOSE:To enable mass spectrometry of high resolution and accuracy by applying an ion beam to a columnar analysis area left after the required area of a sample is subjected to a sputter etching process. CONSTITUTION:The circumference of the analysis area of a sample is subjected to a sputter etching process and thereby a columnar analysis area is formed. When secondary ion mass spectrometry according to secondary ions from the sample is carried out by irradiation of the area with an ion beam, spatial element distribution in the depth of the analysis area can be detected with high resolution and accuracy from high to low density without reading peripheral information. Further the rate of the shift of secondary ions from their orbit due to electrification of a high resistance portion is reduced.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for secondary ion mass spectrometry of a minute region of a sample using a focused ion beam, and in particular, the present invention relates to a method for secondary ion mass spectrometry of a minute region of a sample using a focused ion beam. This invention relates to a secondary ion mass spectrometry method that avoids information contamination and improves the reliability of analytical data. [Prior Art] With the recent trend toward ultra-fine and highly integrated semiconductor devices, slight contamination and other problems may occur during the semiconductor device manufacturing process. Inclusion of microscopic foreign matter adversely affects the operation of the device, often resulting in fatal damage. In addition, due to the remarkable improvement in the cleanliness of semiconductor manufacturing processes, the amount of contamination by these elements and the size of microscopic foreign objects are becoming smaller and smaller, and it is now necessary to detect and analyze these contaminant elements and microscopic foreign objects. Increasingly, higher sensitivity and higher spatial resolution are required for the equipment used to perform these tasks. Secondary ion mass spectrometry
MassS spectroscopy; Hereinafter,
The SIMS method (abbreviated as the SIMS method) has the essential characteristics of high sensitivity that is incomparable to other surface analysis devices and the ability to perform depth direction analysis. There are high expectations for the department's analysis. On the other hand, a focused ion beam (Focus
d Ion Beam (hereinafter abbreviated as FIB) is in the spotlight. The beam diameter of the FIB is focused on the irradiated sample surface to a diameter of about 0.1 μm. Also,
A liquid metal ion source (LiquidMetal Ion 5our) is one of the ion sources that realize FIB formation.
ce; hereinafter abbreviated as LMIS). LMIS is
This is an ion source that attaches the ionic material in a molten state to a needle-like electrode with a sharp tip, and applies a high electric field to the needle-like electrode to ionize the liquid ionic material through field evaporation and field ionization processes. The effectiveness of LMIS is that the emitted ions can be focused to a beam diameter of about 0.1 μm, that the current density at that time is several orders of magnitude higher than the beam obtained with a conventional surface ionization type ion source, and that it is possible to emit ions. This is because there are many ionic species. Adaptation of LMIS to secondary ion mass spectrometers (hereinafter referred to as SIMS devices) has already been attempted, and gallium F using gallium (Ga), which is easy to handle as an ion material, has already been attempted.
Analysis of minute regions using IB (hereinafter abbreviated as GaFIB) is being carried out. This is, for example, the collection of papers "Ultramicroscopy, Volume 24 (1989), pages 97 to 117 (Ultramicroscopy,
24 (1989) 97-117) J (Conventional Example 1). [Problem to be solved by the invention] Conventional Example 1 and other examples show that due to the unique advantages of FIB, such as high current density and submicron diameter, SIMS analysis of extremely small parts, which has not been possible until now, is possible. . However, the Proceedings of the Society of Photo-Optical
Instrumentation Engineering, 1986 (Society of Photo Optical
Instrumentation Engineer
ing) J, when the current density distribution in the radial direction of the FIB is measured in detail, it is found that the distribution has a wider tail like a curved line rather than a Gaussian distribution like curve a shown in Figure 2 (a). It has been reported that (Conventional Example 2) 9 The above current density distribution is one order of magnitude lower (1/1
0), it starts to deviate from the Gaussian distribution, and if it is, for example, 5 digits below the peak (1/105), it will be 3 to 4 times wider than estimated by the Gaussian distribution. A top view of this situation gives an image as shown in FIG. 2(b). Therefore, FI
When performing SIMS analysis using B, this broadening of the current density can be ignored when analyzing only the very superficial layer of the surface or when analyzing an area that is significantly wider than the primary ion beam diameter. As mentioned above, it is becoming impossible to ignore the recent demand for deep analysis in ultra-fine areas and down to lower agricultural degrees. Problems encountered when performing SIMS analysis of a minute area using FIB are shown below. - In concentration distribution analysis in the depth direction, because the current density distribution of the secondary on-beam broadens, information around the desired analysis area is taken in, making low concentration distributions unreliable. ■ If the analysis section has high resistance or an insulating section near the analysis section, the trajectories of the primary beam and secondary ions will deviate from the normal trajectory due to charging on the surface of the high-resistance section or the insulating section, and the obtained data will be distorted. Lacks reliability. ■ When measuring the depth distribution of a low-concentration part in a small area sandwiched between high-concentration parts, if the -order ion beam current density distribution has a tail spread, information from the periphery of the desired analysis area will be taken in, resulting in low concentration. The concentration distribution is unreliable. Below, ■, ■, and ■ will be explained in detail. (2): As explained in FIG. 2, when the current density distribution in the radial direction of the FIB is measured in detail, it is found that the distribution of current density in the radial direction of the FIB is significantly wider several orders of magnitude below the peak than estimated by a Gaussian distribution. Third
The figure is a diagram schematically showing a state in which SIMS analysis is performed by irradiating an ion beam having such a base spread. Figure 3(a) is a top view showing how the beam is scanned during analysis, where 31 is the beam diameter with the half width of the peak in the current density distribution, and 32 is the tail of the beam several orders of magnitude below the peak. The scanning range of the beam, ie, the desired analysis area, is 33. On the other hand, the range in which the tail of the beam hits the sample is wider. The area where the tail sweeps several orders of magnitude below the peak is 34. The sample is a substrate 30 containing an element (impurity) 4 different from the substrate element.
0 is ion-implanted. FIG. 3(b) shows a YY cross section of FIG. 3(a), and the analysis area 33 is sputtered by the analysis ion beam to form a depression, and secondary ions 35 are ejected from the beam irradiation area. .3
5' is emitting. Of course, secondary ions 35' are also emitted from the sample surface portion 37 struck by the skirt portion 32. FIG. 3(c) shows the amount of impurity elements in the secondary ions 35,35' emitted at this time in terms of the relationship between the depth of the analysis section 33 and the number of atoms per unit volume. In other words, the horizontal axis of graph (c) is the impurity concentration (atoms/cm'
), and the vertical axis represents the depth (nm), which indicates that the depth is deeper toward the bottom, and corresponds to FIG. 3(b). This figure is a curve or a concentration distribution obtained by simulation, and shows that the impurity concentration reaches the maximum concentration A near the sample surface and gradually decreases. This impurity concentration distribution depends on the implanted element, implantation energy,
Once conditions such as the amount of implantation and the elements of the substrate to be implanted are known, it is possible to roughly calculate and make predictions. In addition, when the ion implantation process itself is simulated, there is no guarantee that the conditions are exactly as ideal, and the impurity concentration distribution must be based on actual measurements. However, as is clear from the previous explanation, if the secondary ions are emitted purely from the desired analysis area, that is, if the beam tail does not widen, the analysis depth B and impurity concentration B' However, if the beam has a wide tail, secondary ions 35' are also emitted from the surface portion 37 hit by the skirt 32, so impurity measurement at depth B is difficult. The concentration B T+ appears higher than the actual concentration B'. If the beam continues to be irradiated as it is, the impurity concentration distribution obtained will be a curve y as shown by the broken line in Figure (c). Therefore, the impurity concentration distribution curve actually measured in this way lacks reliability. ■,■: As shown in FIG. 4, if an insulating material 42 exists around the analysis region 41 or the sample itself is a high-resistance material, charges 47 are generated in the insulating region 42 by the scanning of the ion beam 46. It accumulates and becomes charged, or the potential on the sample surface changes. For this reason, -order ion beam 46 (44 is the beam diameter with half the peak intensity in the current density distribution, 45
(shows the tail of the beam several orders of magnitude below the peak) is bent as shown in the figure, and the area that should be irradiated to the analysis area 41 is irradiated to the surrounding area 48, and the secondary ion beam is Since the orbit of the object shifts, the data obtained becomes unreliable. Therefore, ideally, it is desirable to have a beam shape that irradiates only the desired analysis area, but in reality, it is difficult to form a beam with no tails, so analysis methods or analyzes that overcome these problems are difficult. The device was desired. The present invention was made in view of the above-mentioned problems, and the purpose is to analyze the elemental distribution in the depth direction of a desired analysis region with high spatial resolution and down to low concentrations without incorporating surrounding information. It is an object of the present invention to provide a method for accurately determining the distribution of ions, and an analysis method for reducing deviations in secondary ion trajectories due to charging of high-resistance parts. [Means for Solving the Problems] In order to achieve the above object, the SIMS analysis method includes a step of leaving a desired analysis region of the sample and sputter etching the periphery of this analysis region using FIB;
This is achieved by a SIMS analysis method characterized by including a step of irradiating the remaining columnar region with an ion beam to emit secondary ions and analyzing the sample. Furthermore, as a method of sputter etching the periphery of the analysis area, for example, as shown in FIG. 5(a), a plurality of rectangles 52, 53, 54, 5
A method such as dividing the film into 5 parts and performing sputtering is used. Here, FIG. 5(b) is the XX section of FIG. 5(a), and is 51
is the analysis part, and 53°55 is the depression after processing. Furthermore, when sputter etching a sample using FIB, F
Depending on the IB scanning method, the sputtered sample may adhere to the sample again, making it impossible to form a rectangular sputter hole, or the sputtered material may adhere to the area that should originally be analyzed. In order to prevent this, in the process of dividing this sputtering area into rectangles and sputter etching, it is necessary to scan parallel to one side of the analysis area and gradually approaching one side of the analysis area as shown in FIG. 6(a). death,
When one side of the analysis area is reached, the focused beam irradiation is terminated and the next rectangular area is sputter-etched, and this process is repeated to leave the desired analysis area 60, thereby removing the substrate material by sputter etching. The analysis area 60 will not be contaminated with redeposited matter. In addition, analysis area 6
Since the size of 0 indicates the spatial resolution of the analysis section, the analysis region 60 left in the sputter etching process should be made as small as possible.9 Although there are many possible ways to divide this sputter etching region, The method shown in b) may also be used. In this way, the analysis area can be created by sputter etching the area around the analysis area using FIB.
The ion beam that irradiates this remaining columnar analysis area is a surface ionization type ion source, a duo plasma type ion source, an L
This is an ion beam emitted from an ion source such as MIS. [Operation] Means for solving the above-mentioned problems will be explained in detail using FIG. 1. FIG. 1(a) is a three-dimensional view showing how an ion beam 3 for analysis is irradiated onto a sample in which the analysis region 1 is left in the form of a column and the peripheral portion thereof is sputter-etched. Figure (b) is a top view of figure (a) for showing the spread of the ion beam irradiated onto the analysis region. Figure (b
), 1 is the analysis area (F-B scanning area), 3' is the beam diameter where the current density is half the peak value, and 3''
4 is the spread of the beam when the current density is several orders of magnitude below the peak value (base part), and 4 is the area where the base part 3'' hits the sample 5 (ion irradiation area), which indicates the desired area where the FIB is actually scanned. Ions are irradiated to a wider area than the analysis region 1. Secondary ions 6 (6', 6'') are emitted from the ion-irradiated sample surface. Originally, the secondary ions 6 that we want as information are those from region 1 (62), and it is desirable that the secondary ions 6'' from region H are not detected.Here, the impurity element concentration near the surface of sample 5 is as shown in the figure. The result is as shown in (d).The concentration is highest just below the surface of the sample and gradually decreases.On the other hand, the area around analysis area 1 has been etched away to a depth h by sputter etching using an ion beam. Therefore, even if information from region H is taken in, the secondary ion 6'' signal from region H will be extremely weak compared to the secondary ion 6'' signal from desired region 1. In this way, the desired crack analysis can be performed. By sputter-etching the high concentration area near the surface of the peripheral area, which is information of interference information, in advance using FIB3, etc., and reducing the intake of interference information due to the tail 3'' of the beam, the reliability of the analysis data obtained is increased. The above objective can be achieved. [Example 1] An example of the present invention will be described below with reference to the drawings. <Example 1> First, the apparatus used will be explained with reference to FIG. The apparatus used in this example consists of two focused ion beam (FIB) irradiation systems 7
1.71', and the sample stage 73 has a mechanism that can be set perpendicular to each ion irradiation axis. The analysis section is a mass spectrometer having a sector type electric field 74 and magnetic field 75. Of course, this part may be replaced with a quadrupole mass spectrometer. FIB77.77 emitted from ion source 76.76'
' is focused by a focusing lens 78.78', and the FIB 77.77' is scanned on the surface of the sample 79 by a deflector 79.79'. These FIB irradiation systems 71 and 71' also include blankers, apertures, etc. Sometimes a small mass separator is attached, but it is omitted from the diagram. The FIB irradiation system 71 has a maximum energy of 50 keV and a high current density (maximum 5 A /
This is an optical system (referred to as the first irradiation system 71) that can irradiate the FIB 77 of cm2), and the ion species used here is gallium. The other irradiation system 71' is for irradiating the FIB 77' for SIMS analysis, and can form an FIB with a maximum acceleration voltage of 20 kV, an ion current density of 0, and a FIB of about 5 A/cm''. 71').The ion species of the FIB for this analysis is cesium.Cesium (Cs) can increase the secondary ionization rate of elements with high ionization potential, such as C, O, H, As, and P. Therefore, it is an indispensable element for the SIMS method.Next, the analysis procedure will be explained. The sample has phosphorus (P) at 100 ke V.
This is a silicon substrate uniformly implanted with ions of 5×10'' atoms/c+++2.
In order to investigate the depth distribution of phosphorus in the m-hole area, a gallium FI was applied around the area of 3 μm on each side so that the 0.5 μm-hole area in the center remained as the analysis area.
Sputter etching processing was performed using B77 (hereinafter abbreviated as Ga-FIB). The sputter etching method using Ga-FIB77 at this time involves dividing into a plurality of rectangular regions as shown in FIG.
Ga-FI from the far side to the analysis area for each of them.
B was scanned repeatedly until the depth reached approximately 1.5 μm. After completing the processing of the first region, similar processing was performed on the second, third, and fourth regions one after another. In this way, in the first irradiation system 71, the 5Q keV Ga-F I B 77 (
Beam diameter = 0.1μmφ, current density: approximately 5A/cm2)
Processing of a silicon columnar analysis part with a height of 1.5 μm and a side of 0.5 μm was completed. Next, the sample stage 73 is rotated 45', and the second irradiation system 71'
Cesium FIB77° (hereinafter referred to as C5-F I
B77') is irradiated onto the analysis section. At this time, work such as focusing C5-FIB 77' is performed at a point far away from the analysis area, and C5-FIB 77' is
Analysis can be started immediately by irradiating one analysis area with a 7° beam. FI B irradiated onto an analysis area of 0.5 μm on each side
77' is a C6 FIB (acceleration energy: 20 keV) with a diameter of 0.1 μm < 6, the ion current on the sample surface was 20 pA, and the current density was about 0.25 A/am. C5-F The secondary ions 72 generated by the irradiation of 77' were taken into the analysis section 74.75 and subjected to mass spectrometry.The purpose of the analysis is the depthwise distribution of phosphorus in the silicon substrate, so the detected ions are not interfering. Considering the ion, we focused on P"Si" and recorded the concentration change in the depth direction. The analysis results are shown in Figure 8. Using the same sample 79, the conventional method (sputter etching around the analysis area) Comparing the depth distribution curve a of impurities obtained by the method of ion beam irradiation without irradiation with the distribution curve obtained by the method of the present invention, curve a decreases approximately three orders of magnitude below the peak. In contrast to the curve where the curve becomes smaller and asymptotic to a certain value, the curve has a distribution that is more than 5 orders of magnitude below the peak.In other words, with this method, the distribution around the analysis area It can be seen that because the analysis was possible without incorporating information into the analysis results, it was possible to measure the distribution down to low concentrations compared to the conventional method.It was confirmed whether the distribution curve obtained by this method was valid. Therefore, when compared with the theoretically determined distribution, it became clear that the distribution up to about 5 digits from the peak almost matched, and it became clear that the SIMS analysis method of the present invention is effective. , 2> Now that the basic idea of the present invention has been disclosed as described above, it is easy to think of applying the present method to various analytes,
Furthermore, it is easy to modify the equipment involved. Next, an analysis example of another sample using a different type of apparatus than that of Example 1 will be shown. The apparatus used in this example consists of a sample processing column 90 and an analysis column 90' as shown in FIG. 9, each of which is connected by a vacuum conveyance path 100. The processing column 90 is equipped with an electron gun 91 and an ion source 92, and can be used for sample observation using an electron beam 93 in a so-called scanning electron microscope mode, and the observation area can be processed using an FIB 95. It is an electron/ion composite device that can perform The purpose of using the electron beam 93 is to avoid excessive sample contamination and damage caused by the ion beam 95 during pre-analysis exploration. On the other hand, the analytical column 90' also uses a combined electron/ion irradiation system. 94.94' is an ion beam deflector. Additionally, there is a mass spectrometer 98 for secondary ion 97 analysis. Sputter etching as described above is performed on the vicinity of the analysis portion of the sample 96 using a processing electronic/ion composite device (analysis column 90'). Of course, the investigation in the analysis department is carried out by the electron beam 93', and the sputter etching process is carried out by the FI.
This is done by B95'. There are four types of samples 96, and sample 96-1 is shown in Figure 10(a).
This is a sample having a minute low-concentration ion-implanted region 102 sandwiched between regions 10 in which high-concentration ions are implanted, as shown in FIG. The amount of ion implantation in the high concentration part 101 is 5×IQ
"atoms/c11]2, and the low concentration region 102 is implanted with I x 1014 atoms/c112 to a width of approximately 1 μm. Measure the impurity distribution in the depth direction of the low concentration region 102, such as sample 96-1. When using the conventional method, secondary ion signals from the high concentration regions 101 on both sides were mixed in due to the tail of the ion beam, making it impossible to obtain reliable data. An example will be shown. First, a high concentration region 101 adjacent to a low concentration region 102 is processed by sputter etching using FIBIO 3 in a processing column 90. Fig. 10(b) shows a cross-sectional view of the state after processing. However, the processed area was processed so that the analysis part 104 remained in a columnar shape.The depth of this processing was approximately 2 μm, and after completing the processing, sample 96-1 was introduced into the analytical column 90'. , the analysis FI R103' is placed in the analysis area 10 as shown in FIG.
4, and secondary ion analysis was performed. An example of sample 96-2 is shown in FIG. This sample is
The ion implantation depth is partially changed, and specifically, arsenic ions are implanted at high energy into the silicon substrate (5
00 keV) L f: The region 111 has a shape in which a low energy injection part (20 keV) 112 is sandwiched in between. The width of the low energy implantation part 112 is approximately 1 μm, and was formed by performing high energy ion implantation using a resist, then removing the resist and implanting low energy ions. According to calculations, the average range RP of implanted ions is approximately 2450 people (500 ke V) and approximately 135 people (20
keV). In the analysis procedure, first, the high energy injection part 111 adjacent to the low energy injection part 112 is processed by sputter etching using the FIB 113 in the processing column 90. FIG. 11(b) shows a cross-sectional view of the state after processing, and the processing area was processed so that the analysis part 114 remained in a columnar shape. The processing depth is approximately 3μm, and the processing width is approximately 0.7μm.
, the width of the processed groove 115 is approximately 7 μm. The groove 115 is large in order to avoid information from being mixed in from the high energy injection part 111, and both ends of the low energy injection part 112 are also slightly etched. After completing the processing of the analysis area in this way, the sample 96-2 is transferred to the analytical column 90.
As shown in Figure 11(c), the analytical FIB113
The concentration distribution of the six ion-implanted elements in the depth direction can be clearly analyzed by secondary ion analysis by irradiating the analysis region 114 with
It was about 4 orders of magnitude lower than the peak concentration. If the SIMS method according to the present invention is not used, it is difficult to measure the depth distribution of implanted elements in a low-energy implanted region sandwiched between high-energy implanted regions such as sample 96-2. Because the concentration area is distributed deeper than in low-energy injection, the low concentration area in the desired analysis area is affected by the high concentration area in the periphery, making the obtained data unreliable. become. Next, if an insulating layer exists in the vicinity 121 of the desired analysis area (Fig. 12, sample 96-3) or has high resistance (the first
Fig. 3, sample 96-4) will be explained. Conventionally, when analyzing these samples, reliable depth analysis was difficult because the trajectories of the -order ion beam and secondary ions deviated due to differences in charge amplifiers and surface potentials. By adding a step of sputter etching the periphery in advance, the above problem could be solved by moving the insulating region 121 away from the desired analysis region 124 or 133 or by removing the high resistance region. Furthermore, the device configuration as shown in Figure 9 [Secondly, the preparation of the analysis sample and the analysis can be performed simultaneously, and since it is not exposed to the atmosphere, it eliminates atmospheric contamination, and the preparation and analysis of the sample can be performed simultaneously. time loss can be reduced. Embodiment 3 In this embodiment, an apparatus for carrying out the present invention, particularly a liquid metal ion source for irradiating an analysis section with a cesium ion beam, will be described with reference to FIG. The liquid metal ion source 140 includes an emitter 141 and a capillary 142, a reservoir 143, an ion extraction electrode 144, an ion material 145, etc., and is operated in a vacuum container 148. As the ionic material 45, Cs (cesium) alone was used. In addition, in Figure 14,
Only the ion source is described, and other ion optical systems such as the flux lens are omitted. The method of operation is as follows. First, the emitter 141 is held in a state slightly protruding from the tip of the capillary 142 by the emitter position adjustment mechanism 147. ionic material 145
The cesium is introduced into the beam server 143 and supplied to the tip of the emitter 141. When a high voltage is applied to the ion extraction electrode 144 in this state, the molten ion material 145 at the tip of the emitter 141 is ionized and ions 146 are emitted. When stable ion emission continues, the emitter 141 slightly protrudes from the tip of the capillary 142 as shown in FIG. 14, and the molten ion material 145 reaches the tip of the emitter 141.
Emitter 1 is kept covered (wet) with
When the wetting of the molten ion material 145 at the tip of the ion material 145 deteriorates, the emitted ion current becomes unstable, and in the worst case, ion ejection stops. In order to maintain stable ion emission for a long time, it is important that the liquid ion material (cesium) 145 is well wetted to the tip of the emitter 141. The emitter 141 was a stainless steel wire rod with a diameter of 0.37 mm, and its tip was electrolytically polished with phosphoric acid to make it sharp. The capillary 142 has an outer diameter of 0.8 mm, an inner diameter Q,
It is a stainless steel pipe with a length of 4mm and a length of 4In111. Up until now, tungsten has been used as material for Emitsuta. Emitters made of tungsten have been widely used and trusted in gallium liquid metal ion sources, but when the ion material is cesium, the reproducibility of wetting is not necessarily good. In other words, even if cesium is wet with the tungsten emitter and stable ion emission continues, the ion emission may suddenly stop because the cesium at the tip of the emitter does not remain wet. In such a case, if an attempt is made to forcibly increase the extraction voltage to extract the ions, the molten cesium will be pulled by the electric field and fall as droplets. These fallen droplets may block the aperture of the lens system (not shown) or adhere to the extraction electrodes, causing abnormal discharge. Therefore, it is an important factor for a liquid metal ion source to select an emitter material that is highly wettable with cesium and whose wettability is not impaired for a long time. In contrast to the tungsten emitter, which has the problems mentioned above, in the case of the stainless steel emitter 142, cesium 1
41, and the emitter tip always remains covered with cesium. In addition, since the ion material cesium is stably supplied to the emitter tip and an excessive extraction voltage is not applied, cesium droplets do not fall and the cesium ion 14 remains stable for a long time.
6 can be released. However, the selection of such emitter materials cannot be determined from physical property values such as viscosity and surface tension of the liquid material, and cannot be determined without actually assembling an ion source and observing the ion emission state for various emitter materials. I can't. In this way, the combination of the stainless steel capillary 142 and the emitter 141 is adopted, and the ion material is 0.0.
When 8g of cesium 145 was put into the reservoir 143 and ions were released, the stability of the total emitted ion current was 1%/2.
It had high stability within 4 hours and continued to release for more than 1000 hours without stopping. With the liquid metal ion source developed as described above, stable secondary ion mass spectrometry using a cesium ion beam becomes possible over a long period of time, and the secondary ion mass spectrometry method according to the present invention shown in Example 1.2 is reliable. We were able to obtain highly accurate analytical results. Effects of the Invention According to the present invention, a SIMS analysis method that accurately determines the elemental distribution in the depth direction of a desired analysis region with high spatial resolution and down to low concentrations without incorporating peripheral information;
Furthermore, it is possible to provide a SIMS analysis method that reduces the deviation of a partial ion beam or secondary ion trajectory due to charging of a high resistance part and obtains highly reliable analysis results.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing an embodiment of the present invention and its principle;
The figure is an explanatory diagram showing the spread of the current density distribution of the ion beam, Fig. 3 is an explanatory diagram showing the problems in the conventional example, Fig. 4 is an explanatory diagram showing the problems in the conventional example, and Fig. 5 is an explanatory diagram showing the problems in the conventional example. An explanatory diagram showing one method for carrying out the sputter etching processing method around the analysis area which is a part of the invention, FIG. 6 is a plan view of the sample processing section showing one method for carrying out the invention, 7th
The figure is a schematic configuration diagram of the device used to implement the present invention, Figure 8 is a graph for explaining the effects obtained by implementing the present invention, and Figure 9 is an application of the present invention to other embodiments. 10, 11, 12, and 13 are cross-sectional views of the sample processing section showing another example for demonstrating the effectiveness of the method of the present invention. , FIG. 14 is a longitudinal sectional view showing a liquid metal ion source which is an embodiment of the present invention. Explanation of symbols 1.33, 41, 51. ...Analysis area, 2.51,5
2, 53.54... Sputter etching processing area 3.50, 77.77'... Focused ion beam 3', 3
1.44・Beam spread when the current density is half of the peak 3”, 32.45・Beam spread when the current density is several orders of magnitude below the peak 4.34・・Current density is several orders of magnitude below the peak Region 5, 30.79...Sample 6.35, 43.72...Secondary ion 71.71' where the spread of the beam hits the sample
...Focused ion beam irradiation system ω Figure 1 Figure ζa) Figure not shown) Men + d) (b) (ri No. 1 (a) ('0) 12 Yono 23 Brown 13 (d) (shi) No 32 (c) 7th L 1 sword

Claims (1)

[Claims] 1. In a secondary ion mass spectrometry method in which a sample is irradiated with an ion beam and secondary ions emitted from the irradiation part are mass-analyzed, a desired analysis area of the sample is left and the analysis area is A secondary ion mass spectrometry method comprising the steps of sputter etching the surrounding area with a focused beam, irradiating the remaining columnar region with an ion beam to emit secondary ions, and analyzing the sample. 2. The secondary ion mass spectrometry method according to claim 1, wherein the focused beam for sputter etching the periphery of the analysis region is particularly a focused ion beam. 3. The secondary ion mass spectrometry method according to claim 1, wherein in the step of sputter etching the periphery of the analysis region, the sputtering region is divided into a plurality of rectangles and sputter etched. 4. The process of dividing into rectangles and sputter etching is performed by scanning parallel to one side of the analysis area and gradually approaching one side of the analysis area, and when reaching the one side, the focused beam irradiation is terminated, and then 2. The secondary ion mass spectrometry method according to claim 1, further comprising a step of sputter etching a rectangular region, and repeating this step to leave a desired analysis region. 5. The ion beam irradiated to the columnar region is an ion beam extracted from any one of a surface ionization type ion source, a duo plasma type ion source, and a liquid metal ion source. The secondary ion mass spectrometry method according to item 1. 6. A secondary ion mass spectrometer characterized by having a focused ion beam irradiation means for sputter etching processing of an analysis sample and an ion beam irradiation means for analysis. 7. The secondary ion mass spectrometry method according to any one of claims 1 to 5, characterized in that the ion beam irradiated to the analysis region is particularly an oxygen ion beam or a cesium ion beam. . 8. A secondary ion mass spectrometry method according to claim 7, wherein the ion source for generating the cesium ion beam is a liquid metal ion source. 9. A liquid metal ion source for emitting cesium ions in a secondary ion mass spectrometer, characterized in that a needle-shaped emitter electrode arranged to emit ions of a molten ion material from its tip is formed of stainless steel. A liquid metal ion source for releasing cesium ions.