JP2500772B2 - Sample preparation method for transmission electron microscope - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission electron microscope sample preparation method used for observing crystal defects in a silicon substrate.

[0002]

2. Description of the Related Art A transmission electron microscope is used as a means for observing crystal defects of a silicon substrate. Conventionally, an ion milling method, a chemical etching method, or the like is known as a method for producing a sample for observation with the transmission electron microscope.

Next, a typical sample preparation method by the ion milling method will be described with reference to the perspective view and sectional view of FIG.

First, as shown in FIG. 2A, a sample made of a silicon substrate is cut into about 5 mm square pieces with a diamond cutter to prepare sample pieces. Next, use an ultrasonic wave machine to adjust the sample holder for the transmission electron microscope to 3 m.
The sample piece 1A of mΦ is processed.

Next, as shown in FIG. 2 (b), the surface (rear surface) opposite to the surface 1 to be observed is thinned to a thickness of about 100 μm using a flat polishing machine or the like, and then, Two
Only the central portion of the sample piece 1A is thinned to a thickness of 10 to 20 μm with a bowl grinder so that the cross-sectional shape shown in FIG.

Finally, as shown in FIG. 2 (d), a sample that can be observed with a transmission electron microscope is obtained by setting the observation section 6 to several hundreds nm or less with an ion milling device.

When a sample is prepared by the chemical etching method, the sample is sliced into the shape shown in FIG. 2 (b) or 2 (c) and then immersed in a chemical etching solution for several hundred nm.
The thickness may be set as follows, and this portion may be used as an observation portion.

[0008]

However, the observable range of the transmission electron microscope sample prepared by the above-mentioned conventional method is about several tens of μm in width, and for example, a small number of crystal defects are observed. In that case, it is necessary to prepare many samples. Further, when the cause of the defect of the LSI is to be elucidated, there are cases where the cause cannot be elucidated because the observation range is limited.

An object of the present invention is to provide a method for preparing a sample for a transmission electron microscope which solves the problem that a wide observation range cannot be obtained by the conventional method.

[0010]

According to the method of preparing a sample for a transmission electron microscope of the present invention, a predetermined surface of a silicon substrate is covered with a photoresist film, and then an edge portion of the silicon substrate surface around the photoresist film is etched. And a step of forming a silicon oxide film on the surface of the silicon substrate including the etched surface after removing the photoresist film and adhering the surface of the silicon oxide film to a polishing substrate.
Polishing or etching the back surface of the silicon substrate bonded to the polishing substrate to expose the silicon oxide film at the end of the silicon substrate.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1A to 1F are a perspective view and a cross-sectional view of a sample piece for explaining an embodiment of the present invention.

First, as shown in FIG. 1A, a sample of a silicon substrate is cut into about 5 mm square with a diamond cutter in the same manner as in the conventional method to obtain a sample piece 2. Next, the surface opposite to the surface 1 to be observed is polished by plane polishing to a thickness of about 30 μm.

Next, as shown in FIG. 1B, a photoresist film 3 is applied to the entire surface on the front surface 1 side, and then the photoresist film 3 at the end portion of the sample piece 2 is removed.

Next, as shown in FIG. 1C, the portion not having the photoresist film 3 is etched to a thickness of several μm by immersing it in an HF-based silicon etching solution.

Next, as shown in FIG. 1D, after removing the photoresist film 3, a silicon oxide film 4 is formed on the surface including the etching surface by a coating method or a sputtering method.
Next, the silicon oxide film 4 side is adhered to a glass plate which is a polishing substrate or a substrate similar thereto with an electron wax or an adhesive similar thereto.

Next, as shown in FIG. 1 (e), an abrasive such as ethylenediamine.
The back surface of the sample piece 2 is polished using pyrocatechol or piperazine. At this time, since the polishing agent that can selectively polish silicon among silicon and silicon oxide film is used,
Polishing is completed when the silicon oxide film is exposed.

For etching the sample piece (silicon) 2, a dry etching method using a mixed gas of CF ₄ and O ₂ or a wet etching method using a mixed solution of hydrofluoric acid, nitric acid and acetic acid can be used. .

Finally, as shown in FIG. 1 (f), after the reinforcing ring 5 is adhered to the sample piece with an adhesive, the silicon oxide film 4 is removed with an HF-based etching solution, and if necessary. Further, the sample piece 2 is made to have a thickness of several hundreds nm by an ion schilling method or the like to be a sample for a transmission electron microscope.

[0019]

As described above in detail, according to the present invention, in the method for preparing a sample for a transmission electron microscope, by thinning the sample as much as possible before ion milling, a wide observation range of 2 mm square or more is obtained. A sample for transmission electron microscope having is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view and a cross-sectional view of a sample piece for explaining a process of an embodiment of the present invention.

2A and 2B are a perspective view and a cross-sectional view of a sample piece for explaining a conventional process for producing a sample for a transmission electron microscope.

[Explanation of symbols]

 1 Surface to be observed 1A, 2 Sample piece 3 Photoresist film 4 Silicon oxide film 5 Reinforcing ring 6 Observation part

Claims (1)

(57) [Claims] 1. A step of covering a predetermined surface of a silicon substrate with a photoresist film, and then etching an end portion of the surface of the silicon substrate around the photoresist film; and a step of removing the photoresist film and then etching the surface. Including the step of forming a silicon oxide film on the surface of the silicon substrate and adhering the surface of the silicon oxide film to the polishing substrate, and polishing or etching the back surface of the silicon substrate adhered to the polishing substrate to end the silicon substrate. And a step of exposing the silicon oxide film, the method for preparing a sample for a transmission electron microscope.