JP2982721B2 - Thin film sample preparation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a thin film sample, and more particularly to a method for preparing a thin film sample capable of monitoring the thickness of a thinned sample by utilizing the interference of light.

[0002]

2. Description of the Related Art Conventionally, a method of preparing a thin film sample is described in, for example, the publication "Electron Microscopy Techniques" (editor: Akira Sotomura, published on August 21, 1989), page 74, line 18 to page 78, 2 Transmission electron microscope (TEM) as described in the row
Used for sample preparation for cross-sectional and planar structure analysis of semiconductor materials and devices. This is because, in order to analyze a device structure using a TEM, it is essential that a sample be thinned on the order of submicrons in order to transmit electrons and obtain a sufficient contrast. Less than,
The steps of the conventional thin film sample preparation method for analyzing a cross-sectional structure will be described with reference to FIG.

First, in a cutting step 101, a portion to be analyzed is cut out from a sample 100 such as a silicon wafer or the like on which an LSI element is formed by cleaving with a glass cutter or a 2-3 mm square with a dicing saw to prepare a sample piece.

[0004] In a bonding step 102, another dummy piece is adhered to the front and back surfaces of the sample piece face-to-face, and solidified while being pressed with a vice so that the adhesive layer becomes thin, thereby producing a sample block.

[0005] In a cutting step 103, the sample block is cut perpendicularly to the sample piece using a low-speed blade (low speed saw) to produce a sample cut piece having a thickness of 1 mm or less.

Mechanical polishing step 1 for both sides of sample cut piece
At 04, planar polishing (see FIG. 3) and bowl polishing (see FIG. 4) are performed in this order. In particular, in bowl polishing, depending on the purpose, coarse polishing using a platen or wheel and abrasive material, and mirror polishing using buff and abrasive material, monitor the sample thickness by changing the color of light transmitted through the sample While thinning as much as possible without destroying the sample (30 to 10 μm).
m).

Next, when the entire surface of the sliced sample is the observation target portion, in the ion polishing step 105, arbitrary irradiation is performed on both surfaces of the sliced sample by an ion polishing apparatus while rotating the sliced sample in a plane. Ar accelerated at an angle
⁺ Irradiate the ion beam to thin the sample until a small hole is opened in the center of the sliced sample (0.2 to 0.1 μm).
m) (see FIG. 5). The small hole at the center of the sliced sample is opened when ion polishing is performed for several to several tens of hours. Thereafter, when the entire surface of the thinned sample is an observation target portion, transmission electron microscope observation 106 is performed.

On the other hand, when the specific fine portion in the sample sliced in the mechanical polishing step is the observation target portion, the transmission electron microscope observation 106 and the ion polishing step 105 are repeated until the specific fine portion can be clearly observed.

[0009]

However, according to the above-mentioned conventional method for preparing a thin film sample, there are the following problems.

The first problem is that when thinning a sample in the bowl polishing step, the sample is destroyed if the thinning is attempted as much as possible.

The reason is that it is difficult to reduce the thickness of the sample to the extent that the sample is not destroyed because the limit of the reduction in the bowl polishing step is unknown. Therefore, the determination of the end time of the bowl polishing largely depends on the subjectivity and experience of the maker.

A second problem is that in order to avoid sample destruction, bowl polishing must be completed before the sample is sufficiently thinned. If ion polishing is performed in a state where the flakes are not sufficiently thinned, it takes time for ion polishing, and the observation field of view becomes narrower, and when the sample is formed of a different material in the device structure, unevenness in ion polishing due to a difference in hardness is caused. It causes adverse effects, such as causing

The reason is that the thickness of the sample is monitored only when the color of the light transmitted through the sample changes when polishing the bowl. The change in transmitted light color corresponding to the change in sample thickness is broad, and the end point of bowl polishing cannot be clearly defined on the order of submicrons.

A third problem is that, in the case of observing a specific minute portion in a sample thinned by ion polishing, ion polishing and transmission electron microscope observation must be repeated to finally complete the sample. It is. In this case, a long time is required for preparing the sample, and the number of times the sample is attached to and detached from the sample stage of the transmission electron microscope is increased, and the possibility of breaking the sample is increased.

The reason is that the change in color of the light transmitted through the sample is as follows.
This is because it is not possible to monitor the film thickness in a minute portion on the order of microns. Therefore, the sample must be thinned little by little by ion polishing while checking the specific fine portion many times with a transmission electron microscope until the target specific fine portion can be clearly observed.

Accordingly, an object of the present invention is to provide a method for preparing a thin film sample which can be thinned as much as possible by mechanical polishing in view of the above-mentioned problems of the prior art.

It is another object of the present invention to provide a method for preparing a thin film sample which minimizes the time spent for ion polishing.

It is a further object of the present invention to provide a method of preparing a thin film sample which can easily monitor the film thickness of a specific minute portion of a thinned sample.

[0019]

In order to achieve the above object, the present invention provides a mechanical polishing step for thinning a sample including a portion to be observed, and an ion polishing step for further thinning the sample thinned in the mechanical polishing step. In the method for preparing a thin film sample including, when thinning in the mechanical polishing step, the sample thickness,
When the thin film material is illuminated with white light, the transmitted light color depends on the thickness ,
It is characterized in that monitoring is performed using changes in reflected light color and interference color. Further, this thin film sample preparation method, when the specific fine portion in the sample thinned in the mechanical polishing step is thinned in the ion polishing step, the thickness of the specific fine portion, the interference color due to the thickness when illuminating the thin film material It is characterized by monitoring using change.

Preferably, the present invention relates to a method for producing a thin film sample, comprising: a mechanical polishing step of thinning a sample including an observation target portion; and an ion polishing step of further thinning the sample thinned in the mechanical polishing step. When the thickness of the sample is reduced in the polishing process, the thickness of the sample is monitored using changes in transmitted light color, reflected light color, and interference color depending on the thickness when the thin film material is illuminated with white light , and the interference color is sharp. The mechanical polishing step is terminated at the time when the condition is satisfied. In addition, this thin film sample preparation method is characterized in that when a specific minute portion in a sample thinned in the mechanical polishing step is thinned in the ion polishing step, the thickness of the specific minute portion is observed with a metallographic microscope, and when the thin film material is illuminated. The method is characterized in that monitoring is performed using a change in interference color due to the thickness of the substrate, and the ion polishing step is terminated when the interference color becomes clear.

Preferably, the present invention provides a method for preparing a thin film sample, comprising: a mechanical polishing step of thinning a sample including an observation target portion; and an ion polishing step of further thinning the sample thinned in the mechanical polishing step. When the sample is thinned in the mechanical polishing step, a thinned sample thickness monitor for monitoring the sample thickness is used, and the thinned sample thickness monitor irradiates white light from one side of the sample to a stereoscopic microscope from the other side of the sample. And a second monitor for observing the sample with the color of light transmitted through the sample and checking the sample thinning state with the color of light reflected from the sample by observing the sample under white light. And a third monitor for observing the sample with a metallurgical microscope and confirming the thinned state of the sample with interference colors appearing on the sample. In this thin film sample preparation method, as the silicon sample becomes thinner in the mechanical polishing step, the transmitted light color confirmed on the first monitor changes in the order of red to orange to yellow, and The reflected light color observed changes in the order of gray to white to transparent, the interference color observed on the third monitor increases in range and changes sharply, the transmitted light color is orange, and the reflected light color is a gray color. In this case, the sample thickness is 10 μm, and when the reflected light color is transparent and the interference color is clear, the sample thickness is several hundred nm. Further, the thin film sample preparation method is characterized in that the mechanical polishing step is completed when the interference color confirmed by the third monitor becomes clear. Further, this thin film sample preparation method, when the specific fine portion in the sample thinned in the mechanical polishing step is thinned in the ion polishing step, at the same time as observing the specific fine portion with a metallographic microscope, the thickness of the specific fine portion, the thin film A thinned sample thickness monitor that monitors using a change in interference color due to the thickness when the substance is illuminated is used, and when the interference color confirmed by the thinned sample thickness monitor becomes clear, The ion polishing step is terminated.

(Function) In the invention as described above, the fact that the sample thickness can be confirmed on the order of submicrons by a change in interference color when the thin film material is illuminated is used for monitoring the sample thickness during the mechanical polishing process. As a result, the end point of the mechanical polishing step becomes clear, and the sample is sliced as much as possible by mechanical polishing. Thereby, much time is not spent in the ion polishing step subsequent to the mechanical polishing step, and the thinning of the sample is achieved before the ion polishing unevenness occurs due to the difference in hardness of the material constituting the sample. Therefore, a thin film sample having a uniform thickness can be manufactured.

Further, when a specific fine portion of the sample thinned by the mechanical polishing step is further thinned by the ion polishing step, the sample thickness is monitored by using a change in interference color, thereby observing the sample with a transmission electron microscope. Since the thickness of the specific minute portion can be confirmed on the order of submicrons without alternately performing the polishing step, the method is simple. For this reason, the sample preparation time is shortened, and sample destruction due to sample handling does not occur.

[0024]

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

(First Embodiment) FIG. 1 is a process diagram for explaining a first embodiment of a thin film sample manufacturing method according to the present invention, and FIG. 2 is a diagram for explaining a mechanical polishing process of FIG. 1 in detail. FIG. 3 is a view showing a state of a sample in a plane polishing step in the mechanical polishing step of FIG. 2, FIG. 4 is a view showing a state of a sample in a bowl polishing step in the mechanical polishing step of FIG. 2, and FIG. FIG. 6 is a diagram showing a state of a sample in the ion polishing step of FIG. 1, and FIG. 6 is a diagram for explaining in detail the thin sample thickness monitor of FIG. 1.

The method of preparing a thin film sample according to the first embodiment is as follows.
This is performed in the case of cross-sectional structure analysis. Referring to FIG. 1, a sample cutting step 1 for cutting out an analysis part from a sample 0 in which a target portion to be observed by a transmission electron microscope is arbitrarily present using a dicing saw or the like, and a cut-out sample A sample bonding step 2 in which another dummy piece is bonded to both sides of the piece to form a sample block, a cutting step 3 in which the sample block is cut using a low-speed saw in a direction perpendicular to the sample piece, and the sample A mechanical polishing step 4 in which the cut pieces are polished into thin pieces using a rough / mirror polishing apparatus, and an ion polishing step 5 in which the thinned sample is polished into thin films using an ion polishing apparatus (FIG. 5). ), A transmission electron microscope observation 6 for observing a thinned sample through the sample cutting step 1 to the ion polishing step 5, and a thinning of the sample to be sliced in the mechanical polishing step 4. Having a sliced sample thickness monitor 7 for monitoring the sample thickness by using an absorption-diffraction and interference of light by a substance. In the case of planar structure analysis, bonding step 2
And cutting step 3 is not required.

Referring to FIG. 2, the mechanical polishing step 4 includes a plane rough polishing step 41 and a plane mirror polishing step 4 shown in FIG.
2 and a bowl rough polishing step 43 and a bowl mirror polishing step 44 shown in FIG.

Referring to FIG. 6, the sliced sample thickness monitor 7 includes a three-stage sample thickness monitor of a first monitor 71, a second monitor 72, and a third monitor 73. The first monitor 71 irradiates white light from the back surface of the sliced sample, observes the surface of the sliced sample with a stereoscopic microscope, and monitors the sample sliced state by the color of light transmitted through the sample (transmitted light color). I do. The second monitor 72 observes the thinned sample under a fluorescent lamp (white light), and monitors the thinned state of the sample based on the color of reflected light from the sample (reflected light color). Third monitor 73
Monitors the sliced sample with a metallographic microscope and monitors the state of the sliced sample from the interference color that appears on the sliced portion when irradiated with white light.

The mechanical polishing step 4 shown in FIG. 2 proceeds in the order of a plane rough polishing step 41, a plane mirror polishing step 42, a bowl rough polishing step 43, and a bowl mirror polishing step 44.

As the monitor 7 for measuring the thickness of the thin sample, the first monitor 71 is used in the bowl rough polishing step 43, and the first monitor 71 and the second monitor 7 are used in the bowl mirror polishing step 44.
Second and third monitors 73 are used sequentially or simultaneously.

When the interference color becomes clear on the third monitor 73, the mechanical polishing step 4 is completed.
After thinning the film until a small hole is formed in a part of the sample, observation with a transmission electron microscope 6 is performed.

The effect of the first embodiment will be described. The first embodiment utilizes a light absorption, diffraction and interference effect of a thin film material to irradiate a thinned sample with white light. The thickness of the thin sample can be monitored on the order of submicron by the transmitted light color, reflected light color, and interference color that appear. For this reason, the end point of sample thinning in the mechanical polishing step can be clarified, and the time spent in the subsequent ion polishing step can be reduced. In addition, the sample can be thinned before ion polishing unevenness occurs due to a difference in hardness of a material constituting the sample. Therefore, a thin film sample having a uniform thickness can be manufactured in a short time.

(Second Embodiment) FIG. 7 is a process chart for explaining a second embodiment of the method for producing a thin film sample according to the present invention. In this figure, the same steps as those in the first embodiment are denoted by the same reference numerals. Further, since the steps from the cutting step 1 to the sliced sample thickness monitor 7 shown in FIG. 7 are the same as those in the first embodiment, the description thereof will be omitted, and only different steps will be described here.

The thin film sample preparation method of the second embodiment is different from that of the first embodiment shown in FIG. 1 in that an ion polishing step 5 and a transmission electron microscope observation 6 are carried out as shown in FIG.
There is a thinned sample thickness monitor 8 between the sample and the target portion to be observed by the transmission electron microscope is not the whole sample thinned by the ion polishing step as in the first embodiment,
This is a portion where the specific fine portion 10A in the sample 10 thinned in the mechanical polishing process is thinned in the ion polishing process.
Note that also in the present embodiment, the bonding step 2 and the cutting step 3 are unnecessary in the case of the planar structure analysis.

The thinned sample film thickness monitor 8 observes the specific minute portion by a metallographic microscope when the specific minute portion 10A of the sample thinned by the mechanical polishing process is further thinned by the ion polishing process, and is irradiated with white light. Specific fine spot 10A
The thinning state of the specific minute portion 10A is monitored by the interference color appearing in the above.

In the second embodiment, while performing the ion polishing step 5 on the specific minute portion 10A of the sample thinned in the mechanical polishing step, the specific minute portion 10A on the order of microns is monitored by the thinned sample film thickness monitor 8. Monitor thickness. That is, the ion polishing step 5 and the thinning sample thickness monitor 8 are repeated to thin the specific minute portion 10A to a desired thickness. After that, observation with a transmission electron microscope 6 of the specific minute portion 10A thinned to a desired thickness 6
I do.

The effect of the second embodiment will be described. In the second embodiment, a metallographic microscope is used for the thinned sample thickness monitor 8 to specify a specific minute portion of a micron order in the ion polishing process. Can be monitored on the submicron order (several tens nm order).
For this reason, the thinning state of a specific minute portion can be confirmed without observing with a transmission electron microscope. Therefore, the sample preparation time can be reduced, and sample destruction due to sample handling can be prevented.

(Other Embodiments) In the mechanical polishing step in the first or second embodiment described above, as shown in FIG. 2, a plane rough polishing step 41 and a plane mirror polishing step 42.
And the bowl rough polishing step 43 and the bowl mirror polishing step 44 are performed, but the present invention is not limited to this, and the bowl rough polishing 43 and the bowl mirror polishing 44 shown in FIG.
The sample may be sliced. That is, when the sample is thinned, the thinning is performed only by the rough surface polishing 41 and the flat mirror polishing 42 while monitoring the thickness of the sample with the thinning sample thickness monitor 7. According to this embodiment, since the sample is sliced only by planar polishing, a wide observation field of view can be obtained.

In the first or second embodiment, the case of manufacturing a thin film sample for observation with a transmission electron microscope has been described. However, a thin film sample used for other microscopes can be manufactured. In addition, a material other than silicon, such as GaAs or glass, can be produced as a sample.

[0040]

Next, each of the above-described embodiments will be described in detail with reference to specific examples.

(First Example) Here, a specific example of a method for producing a thin film sample for analyzing a cross-sectional structure described in the first embodiment will be described with reference to FIGS. 1, 2, 6 and 8. Will be explained.

First, in a cutting step 1 from a sample 0 of a silicon wafer on which an LSI element is formed, an analysis area is cut by a glass cutter or a dicing saw by 2 to 3 mm.
Cut out into corners to make sample pieces.

In a bonding step 2, another dummy piece is adhered to the front and back surfaces of the sample piece face-to-face, and cured while applying pressure with a vice so that the adhesive layer becomes thin, thereby producing a sample block.

In a cutting step 3, the sample block is cut perpendicularly to the sample piece using a low-speed blade (low speed saw) to produce a sample cut piece having a thickness of 1 mm or less.

The sample cut piece is polished in the plane rough polishing step 41 and the plane mirror polishing step 42 of the mechanical polishing step 4 until the thickness of the sample cut piece becomes about 50 μm. afterwards,
Until the first monitor 71 confirms that the color of the light transmitted through the sample piece has changed from red to orange, the bowl rough polishing step 43 is performed on the sample piece for about 3 minutes. At this time, the sample thickness is about 10 μm. Next, in a bowl mirror polishing step 44, thinning is performed slowly while polishing the surface of the sample cut piece to a mirror surface.

As the sample is thinned in the bowl mirror polishing step 44, for example, the transmitted light color, reflected light color, and the like of the sample made of silicon monitored by the first to third monitors shown in FIG.
As shown in the correspondence between the interference color and the sample thickness by the bowl mirror polishing, the transmitted light color of the thin section monitored by the first monitor 71 is step 1 (red) → step 2 (orange) →
Step 4 (yellow) is changed. Also, the second monitor 72
The reflected light color of the thin section to be monitored changes in step 2 (grey) → step 4 (white) → step 6 (transparent). Then, as in step 2, when the transmitted light color monitored by the first monitor 71 is orange, the reflected light color monitored by the second monitor 72 appears as a gray color. The interference color monitored by the third monitor 73 appears faintly in step 5 when the reflected light is changed from white to transparent on the second monitor 72. Then, as the sample becomes thinner, the range of the interference color increases and the image becomes sharper. In step 6 where the interference color becomes clear, the bowl mirror polishing step 44 is completed. When the sample is made of glass, the thickness of the sample cannot be monitored by the colors of the transmitted light and the reflected light since there is no change in the colors of the transmitted light and the reflected light. However, since the interference color changes depending on the thickness even of glass, the thickness of the sample may be monitored using only the third monitor 73 when the sample is glass.

Next, in the ion polishing step 5, the sample thinned while monitoring the thickness as described above is thinned until a small hole is formed in a part of the sample. An electron microscope observation 6 is performed.

(Second Example) Here, a specific example of a method of fabricating a thin film sample in the case of cross-sectional structure analysis described in the second embodiment will be described with reference to FIG. Further, since the present example is the same as the first embodiment from the cutting step to the mechanical polishing step, different steps will be mainly described below.

In FIG. 7, for example, when analyzing a microscopic part of a micron order of a silicon device,
First, in the mechanical polishing step 4 similar to the first embodiment,
The interference color confirmed by the sliced sample thickness monitor 7 is the sample 10
The thin section is made until it becomes clear centering on the specific minute portion 10A.

Next, an ion polishing step 5 is performed on a specific minute portion 10A of the sample sliced in the mechanical polishing step 4.
While repeating the sample thickness monitor 8 and thinning, the specific minute portion 10A is thinned. The interference color becomes sharper as the film thickness is reduced.

FIG. 9 shows the interference color of the thinned sample film thickness monitor when the film thickness is reduced to about 50 nm at a specific minute portion. As shown in FIG.
The color of the interference color in the thinnest state of is cream,
When a transmission electron microscope observation 6 was performed, a lattice image was observed, and the sample film thickness was about 50 nm.

(Third Embodiment) Since the method of preparing a thin film sample of the present invention can be used for preparing a sample for analyzing a planar structure of a silicon device, here, a method of preparing a thin film sample for analyzing a planar structure is described. A specific example of the method will be described with reference to FIG. 1, FIG. 2, FIG. 6, and FIG.

First, in a cutting step 1, a portion to be analyzed is cut into a 2.5 mm square by a dicing saw from a sample 0 of a silicon wafer on which an LSI element is formed, thereby preparing a sample piece. The sample piece is polished in the plane rough polishing step 41 in the mechanical polishing step 4 until the thickness of the sample piece becomes about 50 μm. Thereafter, the bowl rough polishing step 43 is performed on the sample piece for 3.5 minutes until the first monitor 71 confirms that the transmitted light color of the sample piece has changed from red to orange. The sample thickness at this time is about 15 μm. Next, bowl mirror polishing process 4
In 4, the thinning is performed slowly while polishing the surface of the sample piece to a mirror surface.

Here, the transmitted light color, reflected light color and interference color of the sample made of silicon to be monitored by the first to third monitors,
Regarding the relationship with the sample thickness by the bowl mirror polishing process,
This will be described with reference to FIG. In FIG. 8, Step 1 is at the end of the bowl rough polishing step 43. In step 2 after 10 minutes from the start of the bowl mirror polishing process 44,
The transmitted light color monitored by the first monitor 71 is orange, the reflected light color monitored by the second monitor 72 is gray, and the third monitor 7
The interference color monitored in 3 has not yet appeared. The sample film thickness in this state is about 10 μm. Thereafter, the sample thickness in the bowl mirror polishing step 44 is monitored by the sliced sample thickness monitor 7 at intervals of 5 minutes.

In step 3 15 minutes after the start of the bowl mirror polishing process 44, the transmitted light color monitored by the first monitor 71 is orange to yellow, the reflected light color monitored by the second monitor 72 is white, and the third monitor 73 There was no interference color monitored in the above, and the sample film thickness was 7 to 8 μm.

In step 4 20 minutes after the start of the bowl mirror polishing step 44, the transmitted light color monitored by the first monitor 71 is yellow, the reflected light color monitored by the second monitor 72 is white,
There is no interference color monitored by the third monitor 73, and the sample film thickness at this time is 4 to 5 μm. Thereafter, the change in the sample film thickness cannot be confirmed by the transmitted light monitored by the first monitor 71. Therefore, the second monitor 72 and the third monitor
The monitor 73 monitors the thickness of the sample.

At step 5 after 22 minutes from the start of the bowl polishing, the reflected light color monitored by the second monitor 72 appears white to transparent, and the interference color monitored by the third monitor 73 appears faintly. Is 1 to 2 μm.

In step 6 after 23 minutes from the start of bowl polishing, the reflected light color monitored by the second monitor 72 is transparent,
The interference color monitored by the third monitor 73 becomes clear (see FIG. 1).
0), and the thickness of the sample at this time is several hundred nm. If the bowl mirror polishing step 44 is continued any more, the sample will be destroyed. The point at which the interference color clearly appears is determined as the end point of the mechanical polishing step 4, and the mechanical polishing step 4 ends. When the sample is made of glass, the thickness of the sample cannot be monitored by the colors of the transmitted light and the reflected light since there is no change in the colors of the transmitted light and the reflected light. However, since the interference color changes depending on the thickness even of glass, the thickness of the sample may be monitored using only the third monitor 73 when the sample is glass.

Next, an ion polishing step 5 is carried out for about 5 minutes until a small hole is formed in a part of the sample to make a thin film. At this time, the area around the hole is thinned to a thickness of 0.1 μm or less in a region of about 70 μmφ, and observation with a transmission electron microscope 6 is performed at this portion.

[0060]

As described above, the present invention comprises a mechanical polishing step for thinning a sample including a portion to be observed and an ion polishing step for further thinning the sample thinned in the mechanical polishing step. When the sample is thinned, the thickness of the sample is determined by the transmitted light due to the thickness when the thin film is illuminated with white light
A thin film sample preparation method that monitors using changes in color, reflected light color, and interference color to reduce the sample thickness in the mechanical polishing process
Can the endpoint clearly, the thinned sample as possible can be produced. Therefore, it is possible to shorten the next ion polishing step,
Further, it is possible to avoid adverse effects such as non-uniform sample thickness due to uneven ion polishing.

Further, when a specific fine portion of a sample thinned by a mechanical polishing process is thinned by an ion polishing process, the thickness of the specific fine portion is monitored by utilizing a change in interference color due to a thickness when a thin film material is illuminated. Thus, the thinning state of a specific minute portion can be confirmed without observation with a transmission electron microscope. In other words, since there is no sample detachment of the ion polishing device and the sample stage of the transmission electron microscope, the sample preparation time can be reduced,
No sample destruction occurs due to sample handling.

[Brief description of the drawings]

FIG. 1 is a process diagram for explaining a first embodiment of a thin film sample preparation method according to the present invention.

FIG. 2 is a process diagram for describing a mechanical polishing process of FIG. 1 in detail.

FIG. 3 is a view showing a state of a sample in a plane polishing step in the mechanical polishing step of FIG. 2;

FIG. 4 is a view showing a state of a sample in a bowl polishing step in the mechanical polishing step of FIG. 2;

FIG. 5 is a view showing a state of a sample in the ion polishing step of FIG. 1;

FIG. 6 is a diagram for explaining in detail a slice sample thickness monitor of FIG. 1;

FIG. 7 is a process chart for explaining a second embodiment of the thin film sample preparation method of the present invention.

FIG. 8 is a diagram showing a correspondence relationship between a transmitted light color, a reflected light color, and an interference color of a silicon sample monitored by first to third monitors, and a sample thickness by bowl mirror polishing.

FIG. 9 is a diagram showing an interference color of a thinned sample thickness monitor when the thickness of a specific minute portion is reduced to about 50 nm.

FIG. 10 is a diagram showing an interference color by a sliced sample thickness monitor indicating an end point of a mechanical polishing step.

FIG. 11 is a process chart for explaining a conventional method for producing a thin film sample for analyzing a cross-sectional structure.

[Description of Signs] 0 Sample in which the observation target position of the transmission electron microscope is arbitrarily present 1 Sample cutting step 2 Sample bonding step 3 Sample cutting step 4 Sample mechanical polishing step 41 Plane rough polishing step 42 Plane mirror polishing step 43 Bowl coarse Polishing process 44 Bowl mirror polishing process 5 Ion polishing process 6 Transmission electron microscope observation 7 Thinning sample thickness monitor 71 First monitor 72 Second monitor 73 Third monitor 8 Thin film sample thickness monitor 10 Observation purpose of transmission electron microscope Samples containing specific fine spots

Claims (8)

(57) [Claims] 1. A method for preparing a thin film sample comprising: a mechanical polishing step of thinning a sample including an observation target portion; and an ion polishing step of further thinning the sample thinned in the mechanical polishing step. The sample thickness,
When the thin film material is illuminated with white light, the transmitted light color depends on the thickness,
A method for preparing a thin film sample, characterized in that monitoring is performed using changes in reflected light color and interference color. 2. The thin film sample manufacturing method according to claim 1, wherein when the specific fine portion in the sample thinned in the mechanical polishing step is thinned in the ion polishing step, the thickness of the specific fine portion is illuminated with the thin film material. A method for preparing a thin film sample, characterized in that monitoring is performed using a change in interference color due to the thickness at the time of performing the measurement. 3. A thin film sample manufacturing method comprising: a mechanical polishing step of thinning a sample including an observation target portion; and an ion polishing step of further thinning the sample thinned in the mechanical polishing step. The sample thickness,
When the thin film material is illuminated with white light, the transmitted light color depends on the thickness,
A method for producing a thin film sample, characterized in that monitoring is performed by utilizing changes in reflected light color and interference color, and the mechanical polishing step is completed when the interference color becomes clear. 4. The thin film sample preparation method according to claim 3, wherein when the specific fine portion in the sample thinned in the mechanical polishing step is thinned in the ion polishing step, the specific fine portion is observed with a metallographic microscope, The thickness of the specific minute portion is monitored using a change in interference color due to the thickness when the thin film material is illuminated, and the ion polishing step is terminated when the interference color becomes clear. Sample preparation method. 5. A method for preparing a thin film sample, comprising: a mechanical polishing step of thinning a sample including an observation target portion; and an ion polishing step of further thinning the sample thinned in the mechanical polishing step. When thinning, a thinned sample thickness monitor that monitors the sample thickness is used, and the thinned sample thickness monitor is irradiated with white light from one side of the sample, observed with a stereomicroscope from the other side of the sample, and transmitted through the sample. A first monitor for checking the thinned state of the sample with the color of the light obtained, a second monitor for observing the sample under white light and checking the thinned state of the sample with the color of light reflected from the sample, and a metal microscope. A method for preparing a thin film sample, comprising: a third monitor for observing a sample and confirming a state of sample thinning by an interference color appearing on the sample by observation with a sign. 6. The method for producing a thin film sample according to claim 5, wherein as the silicon sample becomes thinner in the mechanical polishing step, the transmitted light color confirmed on the first monitor is in the order of red to orange to yellow. The reflected light color observed on the second monitor changes in the order of gray to white to transparent, the interference color observed on the third monitor increases in range and sharply changes, and the transmitted light color changes to orange. Wherein the sample thickness is 10 μm when the reflected light color is a gray color, and the sample thickness is several hundred nm when the reflected light color is transparent and the interference color is clear. 7. The thin film sample according to claim 5, wherein the mechanical polishing step is completed when the interference color confirmed by the third monitor becomes clear. Production method. 8. The method for producing a thin film sample according to claim 5, wherein when the specific minute portion in the sample thinned in the mechanical polishing step is thinned in the ion polishing step, the specific minute portion is removed. At the same time as observing with a metallographic microscope, a thinned sample thickness monitor is used to monitor the thickness of a specific minute portion using the change in interference color due to the thickness when illuminating the thin film material. A method for preparing a thin film sample, wherein the ion polishing step is terminated when the interference color confirmed by a monitor becomes clear.