JP2006071339A - Analytical sample, sample preparing method and sample analyzing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample preparing method capable of forming an analytical sample containing a film to be analyzed having a minute film thickness without changing the crystal structure of the film to be analyzed. <P>SOLUTION: After a laminated film 1Z is formed, first and second soluble films 20Z and 30Z are selectively removed partially in its thickness direction using an FIB method so as to respectively leave first and second adjacent parts 23 and 33 adjacent to the film 10 to be analyzed. The first and second adjacent parts 23 and 33 are partially dissolved and removed in its thickness direction using a solvent capable of dissolving the first and second soluble films 20Z and 30Z to further reduce the thicknesses t21 and t31 precisely. By this method, the analytical sample 1 suitable for performing analysis using, for example TEM can be prepared. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an analysis sample including a film to be analyzed, a sample preparation method for preparing the analysis sample, and a sample analysis method for analyzing the analysis sample.

  Conventionally, various thin film patterns have been widely used in electronic and magnetic devices (hereinafter referred to as thin film devices) such as thin film magnetic heads and semiconductor devices formed using a thin film formation process. For example, a magnetoresistive (MR) element in which a magnetic thin film or the like is laminated is used in a thin film magnetic head, and a wiring pattern made of a conductive thin film is used in a semiconductor device. When such various thin film patterns are used as analysis target films and analysis such as crystal grain size and composition analysis of the specific region is performed, a transmission electron microscope (TEM) is generally used. However, when TEM is used, it is necessary to process the film thickness of the analysis target region in the analysis target film so as to be thin enough to transmit electrons (for example, about several hundred nm).

As a method for producing an analysis sample having an analysis target film having a thickness suitable for TEM observation, a method using etching (FIB etching method) in which etching is performed by irradiation with a focused ion beam (FIB etching method) is generally used. Yes (see, for example, Patent Document 1). According to the FIB etching method, only a specific region (analysis target region) in the analysis sample having the analysis target film can be thinned relatively uniformly.
JP-A-8-261894

  By the way, in recent years, with the miniaturization of a thin film device, the thin film pattern included therein has been remarkably reduced in thickness, and for example, there is a film having a thickness of 20 nm or less. For this reason, physical properties such as the crystal grain size and composition distribution of the thin film pattern have a greater influence on various characteristics as a thin film device than ever before. Under such circumstances, there is an increasing need for more accurate analysis of physical properties such as crystal grain size and composition distribution in a specific region with respect to the thin film pattern constituting the thin film device.

  However, in the FIB etching method as described above, the film thickness of the processing object is limited to about 50 nm. This is because if the film is made thinner than this, the object to be processed to be the analysis target film is damaged by the ion beam, and the original crystal structure is damaged. Usually, a thin film pattern (analysis target film) in a thin film device is in a state where both surfaces are covered with a non-analysis target film such as a protective film. Therefore, when an analysis sample suitable for TEM observation is prepared by the FIB etching method, if the film thickness of the analysis target film is lower than the processing limit of the FIB etching method (for example, less than 50 nm), the analysis target region However, the non-analysis target film covering the analysis target film cannot be sufficiently removed. That is, the analysis target film remains covered with the non-analysis target film. Here, when the film thickness of the remaining non-analysis target film becomes significantly larger than the film thickness of the analysis target film, a moire image (a striped pattern image) as shown in FIG. Occurs, which causes a problem that the crystal grain size of the analysis target film cannot be measured accurately.

  If argon ion milling is performed instead of the FIB method, the entire thickness of the analysis sample can be reduced to about 30 nm. However, in this case, it is difficult to make the thickness of a certain region uniform, and the accuracy of the analysis result is lacking.

  Further, according to the method using chemical etching, the analysis sample can be made relatively thin, but it is difficult to etch only a specific region, and the entire analysis sample becomes thin. Therefore, it is difficult to handle the analysis sample itself, and it is difficult to specify a desired analysis target region at the stage of analysis.

  The present invention has been made in view of such problems, and a first object thereof is to provide an analysis sample including an analysis target film having a minute film thickness and suitable for accurate analysis of the analysis target film. It is in. A second object of the present invention is to provide a sample preparation method capable of forming the analysis sample with higher accuracy without changing the crystal structure of the analysis target film. A third object of the present invention is to provide a sample analysis method for analyzing an analysis sample prepared by the sample preparation method as described above.

  The analysis sample of the present invention includes an analysis target region, an analysis target film including a support region other than the analysis target region, and first and second support layers facing each other with the analysis target film interposed therebetween. The first and second support layers are each provided only in the region corresponding to the support region, or provided so as to have a smaller thickness in the region corresponding to the analysis target region than the region corresponding to the support region, The analysis target film retains a crystal structure equivalent to the crystal structure at the time of film formation. Here, “equivalent to the crystal structure at the time of film formation” means that a TEM observation image equivalent to that at the time of film formation can be obtained for the analysis target film in the sample for analysis.

  In the analysis sample of the present invention, the first and second support layers facing each other across the analysis target film are provided only in the region corresponding to the support region, or the analysis is performed more than the region corresponding to the support region. Since the thin film is provided in the region corresponding to the target region, even the very thin analysis target film is supported by the first and second support layers in the support region, and in the analysis target region. It is possible to analyze the analysis target film. Furthermore, since the analysis target film has a crystal structure equivalent to the crystal structure at the time of film formation, the crystal structure and various physical properties of the analysis target film at the time of film formation can be analyzed.

The sample preparation method of the present invention includes the following steps (1) to (3).
(1) The 1st process of laminating | stacking in order the analysis object film | membrane containing a support area | region other than an analysis object area | region and this analysis object area | region, and a 2nd soluble film | membrane on a 1st soluble film | membrane.
(2) Using the dry etching method, a part of the first and second soluble films in the thickness direction is left so as to leave the first and second adjacent portions adjacent to the analysis target film in the analysis target region, respectively. A second step of forming first and second recesses facing each other with the analysis target film and the first and second adjacent portions sandwiched in the analysis target region by removing.
(3) Using a solvent capable of dissolving the first and second soluble membranes, the first and second adjacent membranes while leaving portions corresponding to the support regions of the first and second soluble membranes, respectively. A third step of forming a sample for analysis by dissolving and removing at least a portion of the portion in the thickness direction.
Here, the “soluble film” is a film made of an inorganic material or an organic material that can be dissolved by a predetermined solvent.

  In the sample preparation method of the present invention, the analysis target film corresponds to the analysis target region of the first and second soluble films without being affected by the irradiation of the energy beam by including the above steps. Since the portion (the first and second adjacent portions) is thinned, an analysis sample including an analysis target film having a crystal structure equivalent to that at the time of film formation is formed. Further, since the portions corresponding to the support region are left out of the first and second soluble membranes, the analysis target membrane is supported by the first and second soluble membranes in the support region. The sample becomes easy to handle, and the analysis target region can be easily identified.

  In the sample preparation method of the present invention, it is desirable to form the first and second soluble films using aluminum oxide containing 1% or more of argon (Ar). In that case, it is desirable to use a sodium hydroxide (NaOH) solution as a solvent.

  In the sample preparation according to the present invention, in the second step, the first and second recesses are formed by irradiating the focused ion beam, and the first and second soluble films of the first and second soluble films are formed. It is desirable that the thickness of the adjacent portion of the be 50 nm or more.

The sample analysis method according to the present invention includes a sample preparation step of preparing an analysis sample and a sample analysis step of analyzing the analysis sample using a transmission electron microscope. The sample preparation process includes the following processes (1) to (3).
(1) The 1st process of laminating | stacking in order the analysis object film | membrane containing a support area | region other than an analysis object area | region and this analysis object area | region, and a 2nd soluble film | membrane on a 1st soluble film | membrane.
(2) Using the dry etching method, a part of the first and second soluble films in the thickness direction is left so as to leave the first and second adjacent portions adjacent to the analysis target film in the analysis target region, respectively. A second step of forming first and second recesses facing each other with the analysis target film and the first and second adjacent portions sandwiched in the analysis target region by removing.
(3) Using a solvent capable of dissolving the first and second soluble membranes, the first and second adjacent membranes while leaving portions corresponding to the support regions of the first and second soluble membranes, respectively. A third step of forming a sample for analysis by dissolving and removing at least a portion of the portion in the thickness direction.

  In the sample analysis method of the present invention, in the sample preparation step, the analysis target film is not affected by the irradiation of the energy beam, and the portion corresponding to the analysis target region in the first and second soluble films (first And the second adjacent portion) are reduced in thickness, so that an analysis sample including an analysis target film having a crystal structure equivalent to that at the time of film formation is formed. Further, since the portions corresponding to the support region are left out of the first and second soluble membranes, the analysis target membrane is supported by the first and second soluble membranes in the support region. The sample becomes easy to handle, and the analysis target region can be easily identified. In the sample analysis step, the analysis sample is analyzed using a transmission electron microscope, so that the analysis of the crystal structure and various physical properties of the analysis target film at the beginning of film formation can be performed more easily than before.

  The analysis sample of the present invention includes an analysis target region, an analysis target film including a support region other than the analysis target region, and first and second support layers facing each other with the analysis target film interposed therebetween. The first and second support layers are provided only in the region corresponding to the support region, or are provided so as to have a smaller thickness in the region corresponding to the analysis target region than in the region corresponding to the support region. Therefore, when analyzing the analysis target film, it can be easily handled even when the thickness is very thin, and the analysis target region can be easily discriminated. Furthermore, since the analysis target film has a crystal structure equivalent to the crystal structure at the time of film formation, the crystal structure and various physical properties of the analysis target film at the time of film formation can be analyzed. At this time, if the first and second soluble films have a thickness equal to or less than the thickness of the analysis target film in the region corresponding to the analysis target region, the first and second soluble membranes are suitable for more accurate analysis.

  According to the sample preparation method of the present invention, the first soluble film, the analysis target film, and the second soluble film are sequentially stacked, and then adjacent to the analysis target film in the analysis target region using the dry etching method. By removing portions of the first and second soluble films in the thickness direction so as to leave the first and second adjacent parts to be left, respectively, the analysis object film and the first and second films in the analysis object region are removed. First and second recesses that are opposed to each other with an adjacent portion of the first and second soluble membranes being further formed using a solvent capable of dissolving the first and second soluble membranes. Of these, at least a part of the first and second adjacent portions in the thickness direction is dissolved and removed while leaving portions corresponding to the support regions, respectively. Analyze vs. without First and second variable 溶膜 of the portion corresponding to the region, namely the first and second adjacent portion can be thinned with high accuracy. Therefore, it is possible to form an analysis sample having an analysis target film that retains the crystal structure at the time of film formation, and the first and second soluble films that are thinned with high accuracy in the analysis target region. At this time, since the portion corresponding to the supporting region of the first and second soluble layers is left, it can be easily handled even when the analysis target membrane is very thin, and Therefore, the analysis target region can be easily determined.

  According to the sample analysis method of the present invention, in the sample preparation process, the analysis target film retaining the crystal structure at the time of film formation, and the first and second soluble films thinned with high precision in the analysis target region The analysis target area can be easily discriminated, and an analysis sample that can be easily handled can be formed. Therefore, in the sample analysis process, analysis on various physical properties of the analysis target film can be performed more easily. In particular, if the thickness of the first and second soluble membranes according to the thickness of the analysis target membrane is set in the analysis target region, more accurate analysis can be performed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, with reference to FIG. 1 and FIG. 2, the structure of the sample for analysis which concerns on one embodiment of this invention is demonstrated. FIG. 1 is a perspective view illustrating a schematic configuration of an analysis sample 1 according to the present embodiment, and FIG. 2 is a plan view of the analysis sample 1 viewed from an arrow direction II in FIG.

The analysis sample 1 is a laminate in which the first support layer 20, the analysis target film 10, and the second support layer 30 are sequentially laminated on a substrate 40 such as Altic (Al ₂ O ₃ · TiC). A pair of recesses 21 and 31 are formed so that a part of the laminated cross section (YZ plane) has an H shape (FIG. 2). The analysis target film 10 is, for example, a single layer film or a laminated film made of metal, and a specific example is a magnetoresistive effect element in a thin film magnetic head. The analysis target film 10 holds a crystal structure equivalent to the crystal structure at the time of film formation, and the thickness t10 is, for example, 20 nm. The analysis target film 10 includes an analysis target region 10R and a support region 10S extending in the laminated surface. For example, when the analysis target film 10 is analyzed using TEM, electrons are transmitted through the analysis target region 10R. It will be.

The first and second support layers 20 and 30 are made of amorphous aluminum oxide (Al ₂ O ₃ ) containing, for example, 1% or more of argon (Ar), and each correspond to the analysis target region 10R. Recesses 21 and 31 are provided in the region. For this reason, the thicknesses t21 and t31 of the region corresponding to the analysis target region 10R are thinner than the thicknesses t20 and t30 of the region corresponding to the support region 10S. The thicknesses t21 and t31 are each, for example, 5 nm or less, and the thicknesses t20 and t30 are each 100 nm or more.

  Next, a sample preparation method for forming the analysis sample 1 will be described with reference to FIGS. 3 to 5 are cross-sectional views corresponding to FIG. The sample preparation method of this embodiment uses a focused ion beam (FIB) etching method and a chemical etching method in combination.

  First, as shown in FIG. 3, the laminated film 1 </ b> Z is formed on the substrate 40 by sequentially laminating the first soluble film 20 </ b> Z, the analysis target film 10, and the second soluble film 30 </ b> Z (the first film 1 </ b> Z). Process). Here, for example, a sputtering method is used.

  After forming the laminated film 1Z, the first and second adjacent portions adjacent to the analysis target film 10 are irradiated with FIB on the portion corresponding to the analysis target region 10R in the first and second soluble films 20Z and 30Z. Part of the thickness direction (Z direction) of the first and second soluble films 20Z and 30Z is removed so as to leave 23 and 33, respectively (FIG. 4). In this case, for example, FIB is irradiated after the analysis target region 10R is covered with a protective film. By doing so, in the analysis target region 10R, it is possible to form a pair of recesses 21 and 31 that face each other with the analysis target film 10 and the first and second adjacent portions 23 and 33 interposed therebetween (second step). At this time, in order to prevent the analysis target film 10 from being affected by FIB irradiation, etching is performed so that the thicknesses t21 and t31 of the first and second adjacent portions 23 and 33 are not thinner than 50 nm, respectively. Here, the substrate 40 in the region corresponding to the analysis target region 10R is also selectively etched together with the first soluble film 20Z.

  Subsequently, a solvent capable of dissolving the first and second soluble membranes 20Z and 30Z (for example, an alkali solvent such as sodium hydroxide (NaOH) or potassium hydroxide (KOH)) is used to correspond to the support region 10S. A part of the first and second adjacent portions 23 and 33 is further dissolved and removed in the thickness direction while leaving a part of the first and second soluble films 20Z and 30Z. As a result, the thicknesses t21 and t31 are further reduced to 5 nm or less. As described above, the analysis target film 10 that retains the crystal structure at the time of film formation without being affected by the FIB irradiation, and the first and second support layers 20 and 30 that are thinned with high accuracy in the analysis target region 10R. The formation of the analysis sample 1 having the above is completed (third step).

  Subsequently, a sample analysis method according to an embodiment of the present invention will be described with reference to FIG. The sample analysis method of the present embodiment is to analyze the analysis sample 1 obtained by the sample preparation method using a TEM.

  FIG. 6 shows the configuration of the TEM 60 used in the sample analysis method of the present embodiment. The TEM 60 is for observing the internal fine structure using an electron beam having information of the analysis sample 1 obtained by transmitting the analysis sample 10. In TEM, it is possible to perform observation at an atomic level by obtaining a projection image of several tens of thousands times or more, and by irradiating an electron beam, the analysis sample 1 is reflected electrons, Auger electrons or X-rays (characteristic X-rays and Continuous X-rays) are emitted, and various analyzes can be performed using this. For example, by detecting the characteristic X, elemental analysis (elemental qualitative analysis and element distribution state investigation) can be performed.

  In the TEM 60, an electron gun 61 as an electron beam source, an irradiation lens system 62, an imaging lens system 63, and an image sensor 64 are sequentially arranged in a housing (not shown). The analysis sample 1 is provided between the irradiation lens system 62 and the imaging lens system 63. The electron gun 61 is an electron beam source called a thermionic emission type, and includes a cathode (filament) 61A, a Wehnelt 61B, and an anode (acceleration electrode) 61C. The cathode 61A is made of, for example, tungsten (W), and is heated by applying a voltage to emit electrons. Further, a negative voltage is applied to the cathode 61A with the anode 61C as the ground potential. A minus voltage (bias voltage) slightly lower than that of the cathode 61A is applied to the Wehnelt 61B. The Wehnelt 61B focuses electrons from the cathode 61A to form an electron beam bundle having a high electron density. The diameter of the electron beam bundle immediately after passing through the Wehnelt 61B is, for example, about 10 μm to 30 μm. The anode 61C functions to accelerate the electron beam bundle from the Wehnelt 61B.

  The irradiation lens system 62 includes first and second focusing lenses 62A and 62B, and irradiates the sample 1 for analysis with the electron beam bundle from the electron gun 61. The imaging lens system 63 includes an objective lens 63A and an intermediate lens 63B for enlarging the electron beam bundle that has passed through the analysis sample 1, and a projection lens 63C for forming an image on the imaging element 64. . The imaging device 64 is, for example, a charge coupled device (CCD).

  In the TEM 60 having such a configuration, first, the inside of the housing is evacuated. Next, electrons are emitted by heating the cathode 61A, and are converged in the Wehnelt 61B to form an electron beam bundle having a high electron density. Further, the electron beam bundle is accelerated by the anode 61C and directed to the irradiation lens system 62. To radiate. The electron beam bundle is narrowed down to a minute spot diameter by the irradiation lens system 62 and irradiated to the analysis sample 1. Since the irradiated electron beam bundle passes through the analysis sample 1, an observation image of the internal structure of the analysis sample 1 can be obtained by projecting this onto the image sensor 64 through the imaging lens system 63. A fluorescent screen may be used instead of the image sensor 64.

  As described above, according to the present embodiment, first, the FIB method is used to first leave the first and second adjacent portions 23 and 33 adjacent to the analysis target film 10 in the analysis target region 10R. By selectively removing a part of each of the second soluble films 20Z and 30Z in the thickness direction, a pair of concave portions 21 and 31 facing each other with the analysis target film 10 interposed therebetween are formed in the analysis target region 10R. Thus, for example, higher dimensional accuracy can be ensured and processing can be easily performed in a shorter time compared to photolithography, for example.

  Thereafter, by using a solvent capable of dissolving the first and second soluble films 20Z and 30Z, a part of the first and second adjacent portions 23 and 33 in the thickness direction is dissolved and removed, and the thicknesses t21 and t31 are accurately determined. Since the thickness is made much thinner, an analysis sample 1 suitable for performing an analysis using a TEM can be produced. Here, since the FIB irradiation is not affected on the analysis target film 10, the crystal structure of the analysis target film 10 is not changed. Furthermore, since the first and second support layers 20 and 30 have a larger thickness in the region corresponding to the support region 10S than in the region corresponding to the analysis target region 10R, the analysis target film 10 is in the support region 10S. It will be supported by the first and second support layers 20 and 30. Therefore, even when the thickness t10 of the analysis target film 10 is very thin, it can be easily handled, and the analysis target region 10R can be easily determined.

  Further, since the analysis target region 10R of the analysis sample 1 is analyzed using the TEM, the in-plane state of the analysis target film 10 retaining the crystal structure at the time of film formation is accurately analyzed. Can be performed easily.

  Next, specific examples in the above embodiment will be described. In this example, based on the sample preparation method in the above embodiment, the analysis sample 1 was prepared, and the analysis target region 10R was observed by TEM.

Specifically, first, a first soluble film 20Z made of 200 nm thick Al ₂ O ₃ and a 20 nm thick iridium manganese alloy (IrMn) are formed on a substrate 40 made of silicon (Si) by sputtering. The target film 10 to be analyzed and the second soluble film 30Z made of 200 nm thick Al ₂ O ₃ were sequentially stacked to form a stacked film 1Z. Next, after the laminated film 1Z was cut out by dicing, the first and second soluble films 20Z and 30Z were selectively removed using the FIB etching method so that the thicknesses t20 and t30 were 50 nm, respectively. After that, by immersing in 4N (N) NaOH maintained at 40 ° C. for 10 minutes and dissolving and removing part of the first and second soluble films 20Z and 30Z, the thicknesses t20 and t30 are reduced. Each was 5 nm or less. At the same time, only FIB etching was performed on the laminated film 1Z so that the thickness t1 of the analysis target region 10R was 30 nm, and a sample for analysis as a comparative example was manufactured.

  When the analysis sample 1 of the present example produced as described above was observed with a TEM, as shown in FIG. 7A, an observation image with a small moire image was obtained, and the crystal grain size, etc. It was confirmed that accurate analysis was possible. On the other hand, in the case of the analysis sample as a comparative example produced only by the FIB etching method, a moire image is generated as shown in FIG. It was difficult.

  As described above, according to the present embodiment, by using the FIB etching method and the chemical etching method in combination, the first and second soluble components in the analysis target region 10R can be obtained without altering the crystal structure of the analysis target film 10. Since the films 20Z and 30Z are processed to be sufficiently thin, an observation image with a small moire image can be obtained when performing an analysis by TEM, and an accurate analysis of various physical properties of the analysis target film 10 is possible. It could be confirmed.

  The present invention has been described above with reference to some embodiments and examples. However, the present invention is not limited to the above embodiments and examples, and various modifications can be made. For example, in the above embodiments and examples, the first and second soluble films in the region corresponding to the analysis target region are left thin so as to cover the analysis target film. When deterioration such as oxidation does not become a problem, the first and second soluble films in the region corresponding to the analysis target region may be completely removed and left only in the region corresponding to the support region. In that case, the generation of moire images can be completely prevented.

In the present embodiment and example, the first and second soluble films are formed of Al ₂ O ₃ and NaOH is used as a solvent for dissolving the first and second soluble films. However, the present invention is not limited to this. is not. For example, the first and second soluble films may be made of silicon (Si).

  In the above embodiment, the FIB etching method is used as the dry etching method, but another dry etching method may be used. Alternatively, a laser etching method of irradiating laser light may be used in combination with the dry etching method.

  In the above embodiment, the case where the analysis sample is analyzed by irradiating the electron beam with TEM has been described. However, the present invention is not limited to this. For example, an analysis method for performing analysis by irradiating X-rays or ion beams can be used. Examples of such analysis techniques include X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), or Rutherford backscattering analysis (RBS). Spectrometry).

The sample preparation method and sample analysis method of the present invention can be suitably used for analysis of various thin film patterns included in electronic / magnetic devices such as semiconductor elements and magnetoresistive elements, for example.

It is a perspective view showing schematic structure of the sample for analysis concerning one embodiment of the present invention. It is a top view showing the plane structure of the sample for analysis shown in FIG. It is a top view showing 1 process in the sample preparation method concerning one embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a process following FIG. 3. FIG. 5 is a plan view and a cross section showing one process following FIG. 4. It is the schematic showing the structure of TEM used in the sample analysis method which concerns on one embodiment of this invention. It is a TEM observation image in the analysis object area | region of the sample for analysis shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Analytical sample, 1Z ... Laminated film, 10 ... Analysis object film | membrane, 10R ... Analysis object area | region, 10S ... Support area | region, 20 ... 1st support layer, 20Z ... 1st soluble film | membrane, 21, 31 ... Recessed part, 22 , 32 ... bottom surface, 23, 33 ... adjacent part, 30 ... second support layer, 30Z ... second soluble film, 40 ... substrate, 60 ... TEM, 61 ... electron gun, 62 ... irradiation lens system, 63 ... imaging Lens system, 64... Image sensor.

Claims (9)

An analysis target membrane including an analysis target region and a support region other than the analysis target region;
First and second support layers facing each other across the analysis target film,
Each of the first and second support layers is provided only in a region corresponding to the support region, or has a smaller thickness in a region corresponding to the analysis target region than in a region corresponding to the support region. Provided in
The analysis sample characterized in that the analysis object film has a crystal structure equivalent to the crystal structure at the time of film formation. The analysis sample according to claim 1, wherein the first and second support layers are made of amorphous aluminum oxide containing 1% or more of argon (Ar). On the first soluble membrane, a first step of sequentially stacking an analysis target region and an analysis target membrane including a support region other than the analysis target region, and a second soluble membrane;
Using dry etching, a part of the first and second soluble films in the thickness direction is removed so as to leave the first and second adjacent portions adjacent to the analysis target film in the analysis target region, respectively. A second step of forming first and second recesses facing each other across the analysis target film and the first and second adjacent portions in the analysis target region;
Using the solvent capable of dissolving the first and second soluble membranes, the first and second soluble membranes, while leaving portions corresponding to the support regions, respectively, of the first and second soluble membranes. And a third step of forming a sample for analysis by dissolving and removing at least a part of the adjacent portion in the thickness direction. The sample preparation method according to claim 3, wherein the first and second soluble films are formed using aluminum oxide containing 1% or more of argon (Ar). The sample preparation method according to claim 4, wherein a sodium hydroxide (NaOH) solution is used as the solvent. The sample preparation method according to any one of claims 3 to 5, wherein the first and second recesses are formed by irradiation with a focused ion beam. The said 2nd process WHEREIN: The thickness of the said 1st and 2nd adjacent part of the said 1st and 2nd soluble membrane shall be 50 nm or more. Any of the Claims 3-6 characterized by the above-mentioned. 2. The sample preparation method according to item 1. The sample preparation method according to any one of claims 3 to 7, wherein in the first step, the analysis target film is formed to have a thickness of 20 nm or less. A sample preparation process for preparing a sample for analysis;
A sample analysis step of analyzing the analysis sample using a transmission electron microscope,
The sample preparation process includes
On the first soluble membrane, a first step of sequentially stacking an analysis target region and an analysis target membrane including a support region other than the analysis target region, and a second soluble membrane;
Using dry etching, a part of the first and second soluble films in the thickness direction is removed so as to leave the first and second adjacent portions adjacent to the analysis target film in the analysis target region, respectively. A second step of forming first and second recesses facing each other across the analysis target film and the first and second adjacent portions in the analysis target region;
Using the solvent capable of dissolving the first and second soluble membranes, the first and second soluble membranes, while leaving portions corresponding to the support regions, respectively, of the first and second soluble membranes. A third step of forming a sample for analysis by dissolving and removing at least a part of the adjacent portion in the thickness direction.

Images