JPH1019751A - Method of making sample for transmission type electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of making a transmission type electron microscope which enables the obtaining of a clear image of the electron microscope by reducing the roughness of the shape of an observing surface. SOLUTION: The bottom surface of a flat substrate 2 is stuck on a flat specimen 1. Subsequently, after the grinding of the backside of the specimen, a sample piece is cut out flat by a dicer in a size that allows mounting thereof in a mirror body of an electron microscope. Then, the top surface of the specimen 1 is left as thin as possible so that an observing location is contained from the rear of the specimen 1 to shorten FIB(focused ion beam) working time and side rim parts of the sample is worked by the dicer along the length thereof so that the cross section thereof orthogonal to the longitudinal direction of the sample piece is made convex. Finally, the specimen 1 is produced having an FIB worked place 3 thinned to a thickness that allows observation of the observing surface with a transmission type electron microscope from the surface thereof using the FIB.

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 transmission electron microscope sample, and more particularly to a transmission electron microscope (TEM) in which an observation point is formed by a focused ion beam (FIB).
e) relates to a method for preparing an observation sample.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional method for manufacturing a transmission electron microscope sample and an explanatory diagram of a problem. Conventionally, first,
As shown in (a), the sample 1 is large enough to be mounted in the body of an electron microscope with a dicer (for example, about 0.2 mm × 2
(mm × 0.5 mm). When the sample 1 is a wafer, the sample 1 is cut out to a thickness of the wafer.

Then, as shown in FIG. 3 (b), the upper surface is left as thin as possible so as to include the observation point 5 in order to shorten the FIB processing time in the next step, and both side edges are formed. The sample 1 is processed in a longitudinal direction by a dicer so that a cross section orthogonal to the longitudinal direction of the sample 1 has a convex shape. Finally, as shown in FIG. 3 (c), the observation portion 5 is thinned using FIB to the extent that it can be observed from the surface with a transmission electron microscope, and a sample is prepared.

[0004]

However, in the above-described conventional manufacturing method, the surface shape of the sample 1 is reduced at the FIB processing location 3 where the observation location 5 shown in FIG.
Alternatively, a difference in etching rate occurs due to a difference in the internal structure and constituent elements, and the observation surface may be rough, which hinders the observation during the TEM observation as shown in FIG. However, there is a problem that a clear electron microscope image cannot be obtained.

[0005] The present invention has been made in view of the above points,
An object of the present invention is to provide a method for manufacturing a transmission electron microscope sample capable of reducing roughness of the shape of an observation surface and obtaining a clearer electron microscope image.

[0006]

In order to achieve the above object, the present invention provides a first step of attaching a bottom surface of a flat substrate to the surface of a sample, and a back surface opposite to the surface of the sample to which the substrate is attached. A second step of polishing the sample, a third step of cutting the sample and the substrate into a flat plate shape large enough to be mounted in the body of the electron microscope, and a step of cutting the upper surface so as to include the observation point from the back surface of the sample. A fourth step in which both sides are processed in the longitudinal direction and the cross section perpendicular to the longitudinal direction of the sample is formed in a convex shape, and the observation point can be observed from the surface with a transmission electron microscope And a fifth step of thinning the film to an appropriate thickness.

In the method of the present invention, the back surface of the sample which is not attached to the flat substrate is polished, and then the polished surface is thinned so as to include an observation portion. The roughness of the observation surface due to the difference in etching rate due to the difference can be reduced.

In the present invention, the substrate is a transparent substrate, and before the substrate is pasted, on the side where the sample is adhered to the substrate,
In addition, the method is characterized in that it includes a step of marking at a position near the place to be observed. Thereby, the marking position and the thickness of the sample can be identified from the back side of the sample by the color of the transmitted light.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of a first embodiment of a method for producing a transmission electron microscope sample according to the present invention, and FIG.
FIGS. 4A to 4C are views showing a sample before dicing, FIGS. 4D and 4E are views showing a sample during dicing, and FIG. Explanatory drawing of the sample after FIB processing, and FIG. 9 (g) shows a TEM observation state diagram.

In this embodiment, first, a flat bottom surface of a substrate 2 is attached to a flat sample 1 shown in FIG. 1A, as shown in FIG. 1B. This is because Sample 1 has a small thickness and is difficult to polish as it is. Here, the sample 1 has a circuit pattern formed on a semiconductor substrate, and the substrate 2 is attached as a dummy wafer on the circuit pattern. Subsequently, as shown in FIG. 1C, the back surface of the sample 1, that is, the semiconductor substrate is polished. Next, as shown in FIG. 1 (d), the sample is cut into a flat plate having a size such that the sample can be mounted in the body of an electron microscope with a dicer.

Next, as shown in FIG. 1 (e), the sample 1 is processed from the back side with a dicer so as to include the observation point of the sample 1 and to shorten the FIB processing time of the next stage. Then, the upper surfaces of the sample 1 and the substrate 2 are left as thin as possible, and both side edges are formed so that the cross section orthogonal to the longitudinal direction of the sample in the longitudinal direction has a convex shape. Finally, FIG.
As shown in (f), a sample 1 is formed in which the FIB processing site 3 is formed by thinning the observation site from the surface to a thickness that allows observation with a transmission electron microscope using FIB.

In this embodiment, since the FIB processing place 3 is formed on the polished back surface of the sample 1, the surface is flat and the composition is uniform, so that the roughness of the observation surface due to the difference in the etching rate during processing is reduced. it can. Therefore, as shown in FIG. 1 (g), a clear electron microscope image is obtained during the TEM observation, particularly on the back side of the sample 1.

FIG. 2 is an explanatory view of a main part of a second embodiment of the method of the present invention. In this embodiment, before the cross-section forming step using the focused ion beam (FIB), FIG.
As shown in FIG. 2, after performing marking 4 by etching with a FIB or a laser marker on the surface of the sample 1 and near a specific portion 5 to be observed, as shown in FIG. The transparent substrate 6 is attached to the surface on the side where the marking 4 is provided.

Thereafter, a transmission microscope sample can be manufactured through the steps shown in FIGS. 1 (c) to 1 (f). Here, in each of these steps, when performing each processing on the back surface of the sample 1, the color and brightness of the transmitted light seen through the transparent substrate 6 and the sample 1 are different between the marking 4 and other portions. In addition, since the color changes according to the thickness of the sample 1, it serves as a mark for cutting by the dicer and FIB processing, so that a specific portion can be accurately observed, and
Work time can also be reduced.

The applicant of the present invention has previously filed Japanese Patent Application No. 4-332.
Japanese Patent Application Publication No. 845 discloses a transmission electron microscope sample preparation method in which a sample surface is irradiated with FIB, an appropriate marking is made by etching, and then the sample is cut out. Unlike the method, the sample is polished from the side of the marking, and there is no step of polishing the sample after attaching the substrate to the sample.

The present invention is not limited to the above-described embodiment. For example, the substrate 2 may have a thickness of about 500
A μm quartz substrate can be used. When this transparent substrate is used as the substrate 2, when the sample 1 has a thickness of 10 to 20 μm, white light is incident on the transparent substrate and the color of transmitted light seen through the transparent substrate and the sample 1 (silicon substrate) is red. As shown in the figure, the thickness can be used as a standard, which is effective in shortening the polishing time of the sample 1.

[0017]

Next, an example of the first embodiment will be described. The substrate 2 attached on the surface of the sample 1 shown in FIG. 1B is a silicon (Si) substrate having a thickness of about 500 μm. The sample 1 shown in FIG. 1C has a circuit pattern formed on a silicon (Si) substrate, and the back surface (the side on which the Si substrate exists) after polishing has a thickness of about 10 to 10. 20 μm. In addition, as shown in FIG. 1D, the size of the sample cut out by the dicer and composed of the sample 1 and the substrate 2 can be mounted in the body of the electron microscope.
It is about 0.2 mm x 2 mm x the thickness of the sample (about 0.5 mm).

Next, the upper surface is set to a thickness of about 20 μm and the height is set to about 50 μm so that the observation point is included from the back of the sample 1.
1E, the both side edges shown in FIG. 1E are machined in the longitudinal direction with a dicer so that the cross section orthogonal to the longitudinal direction of the sample 1 has a convex shape. Thereafter, as shown in FIG. 1 (f), the portion to be observed is thinned by using a FIB to a thickness such that it can be observed from the surface with a transmission electron microscope.

Next, in the example of the second embodiment, the sample 1 is a silicon substrate having a thickness of 10 to 20 μm on which a circuit pattern is formed, and the transparent substrate 6 as a dummy wafer to be adhered to the surface is a thick substrate. The quartz substrate had a thickness of about 500 μm. According to this embodiment, when white light is incident on the transparent substrate 6, the color of the transmitted light that is seen through the transparent substrate 6 and the sample 1 is dark red, for example, where the marking 4 is not applied. Since the place where the marking 4 is applied is thin, it looks bright red and the location of the marking 4 can be clearly identified.

Further, the color of the transmitted light of the transparent substrate 6 and the sample 1 changes sequentially from red to orange and yellow as the thickness of the sample 1 becomes thinner. Since the marking position and the thickness of the sample can be identified based on the brightness, it is possible to produce a sample that is thinned accurately and includes a portion to be observed in a short time. In addition,
The incident light may be light other than white light.

[0021]

As described above, according to the present invention,
After polishing the back surface of the sample that is not attached to the flat substrate, the polished surface is thinned to include the observation point, so that the difference in the etching rate due to the difference in the surface shape and material of the sample can be observed. Since the surface roughness can be reduced, a clearer electron microscope image can be obtained as compared with the related art, and the quality of observation of the internal structure of the sample by the electron microscope can be improved.

Further, according to the present invention, there is provided a step of forming a transparent substrate as a substrate and, before attaching the substrate, marking the sample on the side where the sample is to be attached to the substrate and in the vicinity of the place to be observed. By including, since the marking position and the thickness of the sample can be identified by the color of the transmitted light from the back side of the sample, it is possible to produce a thinned sample accurately and to include the observation portion in a short time. .

[Brief description of the drawings]

FIG. 1 is an explanatory view of a first embodiment of the method of the present invention and TE
It is an M observation state diagram.

FIG. 2 is an explanatory view of a main part of a second embodiment of the method of the present invention.

FIG. 3 is an explanatory diagram of an example of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sample 2 Substrate 3 FIB processing place 4 Marking 5 Observation place 6 Transparent substrate

Claims (4)

[Claims] A first step of attaching a bottom surface of a flat substrate to a surface of a sample; a second step of polishing a back surface of the sample opposite to an attachment surface of the substrate; and the sample and the substrate. A third step of cutting out the sample into a flat plate shape in such a size that it can be mounted in the body of the electron microscope, and leaving the upper surface so as to include the observation point from the back surface of the sample, and extending both side edges in the longitudinal direction. A fourth step of processing so that a cross section orthogonal to the longitudinal direction of the sample has a convex shape, and thinning the observation portion from the surface to a thickness that allows observation with a transmission electron microscope. A method for producing a transmission electron microscope sample, comprising: a fifth step. 2. The method according to claim 1, wherein the substrate is a transparent substrate. 3. The method according to claim 2, further comprising the step of, before attaching the substrate, marking the sample on the side where the sample is to be attached to the substrate and at a position near a place to be observed. A method for preparing a transmission electron microscope sample. 4. The semiconductor device according to claim 1, wherein the sample is a sample in which a circuit pattern is formed on a semiconductor substrate, and the semiconductor substrate is polished in the second step. The method for preparing the transmission electron microscope sample described in the above.