JP2005055387A - Method for making sample - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily making a transmission electron microscopic sample without requiring an exclusive device. <P>SOLUTION: This method for making a sample comprises thinning a sample piece 2 that becomes the transmission electron microscopic sample, forming a pattern by a photo resist 3 followed by etching, and polishing a formed etched part 4 by an ion milling device to form an observation part 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sample preparation method for observation with a transmission electron microscope.

  A typical method for producing a transmission electron microscope observation sample from a silicon substrate by a conventional ion milling method will be described with reference to FIG.

  First, using a dicing saw or the like, a sample of a silicon substrate is cut out to about 10 mm square. Next, in order to match with the sample holder of the transmission electron microscope, a 3 mmφ sample piece was processed by a punching machine in the state of FIG. 2A, and 2 represents the sample piece. Next, FIG. 2B shows a state in which the thickness is reduced to about 100 μm from the opposite side of the surface to be observed using a flat polishing machine or the like, and 1 indicates an observation surface. Further, the central portion of the sample piece is processed to a thickness of 10 to 20 μm with a bowl polishing machine or a dimple machine so as to have a cross-sectional shape as shown in FIG. Finally, the observation part is set to several hundreds to several tens of nanometers or less by an ion milling apparatus, and a transmission electron microscope sample is shown in FIG. 2D, and 5 denotes the observation part.

  As another conventional example, there is a FIB (Focused Ion Beam) method, which is a method of thinning a specific portion of a sample with Ga ions or the like with high accuracy. The sample as described above can also be prepared by this method. An example of a sample preparation apparatus for transmission electron microscope observation by the FIB method is disclosed in Patent Document 1 below.

JP 2002-062226 A

  However, in the sample preparation method based on the ion milling method, it is necessary to prepare devices such as a dimple grinder and a bowl grinder. These devices are expensive and are not used in other sample preparation or processes, and transmission electron It is necessary to prepare a dedicated device for microscopic sample preparation. If these dipping devices are not provided, the process must be omitted and ion milling must be performed. In such a case, a place where ion milling is usually completed in about 5 hours is required for 20 to 100 hours. Very inefficient.

  Further, in this conventional method, due to the limitations of the ion milling time and the dimple process, it was necessary to polish the sample thickness to 100 μm by polishing with a flat polishing machine or the like. In this respect as well, there is a problem that the end portion of the sample is easily chipped.

  In another sample preparation method using FIB in the conventional method, Ga ions having a large ion radius are used to thin a specific portion, and therefore an amorphous layer usually occurs on the surface of the observation surface from several nm to several tens of nm. This hinders high-magnification observation in a transmission electron microscope.

  In this situation, the object of the present invention is to solve the above-mentioned problems of the conventional method, and provide a sample preparation method for observation with a transmission electron microscope that is simpler than the conventional method and does not require a dedicated device. It is to be.

  The sample preparation method of the present invention is a sample preparation method for observation with a transmission electron microscope, wherein a pattern is formed with a photoresist on a substrate to be a sample, and an etching process is performed only on a predetermined portion; And a step of performing polishing by an ion milling device at a place where the treatment has been performed.

  Supplementally, the present invention does not require a dedicated machine as in the prior art and uses a photoresist process and an etching process apparatus that are indispensable for a process of handling a material such as silicon, thereby patterning a sample to obtain a predetermined pattern. Thus, a method for producing a sample for observing an electron microscope in a short time is provided by using a step of thinning the portion by chemical reactive etching.

  According to the present invention, in a sample preparation method for observation with a transmission electron microscope, it is possible to easily thin a part of a sample without performing dimple processing before performing ion milling. Moreover, in terms of damage to the sample, in contrast to the 80-90 μm depression by the conventional mechanical processing method of dimple processing, since the processing method by chemical reaction etching in the present invention, dislocations and defects are generated in the sample. It is clear that the possibility is extremely small compared to the conventional method.

  Furthermore, if the present invention is used, it can be said that the sample preparation time can be shortened without purchasing a new expensive dimple device.

  Further, according to the present invention, since the etching process can be performed exceeding 200 μm, the thickness of the sample when processed by the flat surface polishing machine can be increased to about 200 μm as compared with the conventional case. That is, the thickness of the edge of the final sample is much thicker than that of the conventional sample, and there is no fear of the lack of the edge, so that the convenience of sample handling is significantly superior to the conventional method.

  The best mode for carrying out the present invention will be described in detail below.

  Fig.1 (a)-FIG.1 (f) are figures which show the state of the sample for showing the sample preparation method of this invention. First, as shown in FIG. 1A, a sample of a silicon substrate is cut into a 10 mm square with a dicing saw in the same manner as in the conventional method, and then a disk-shaped sample piece that is aligned with a sample holder of a transmission electron microscope. Get 2. Further, polishing is performed from the opposite side of the surface to be observed with a flat polishing machine to a thickness of about 200 μm, and a sample as shown in FIG. 1B is obtained. Reference numeral 1 denotes an observation surface.

  Next, as shown in the cross-sectional view of FIG. 1C, a selective hole pattern is formed on the observation side surface of the sample using a photoresist process. Reference numeral 3 denotes a photoresist.

  Next, FIG. 1D shows a state where the selective opening portion is subjected to silicon etching by selective etching using a silicon etching solution made of a mixture of hydrofluoric acid and nitric acid. 4 is an etching part. In this example, 180 μm etching was performed.

  Next, the state where the photoresist in the photoresist process is removed is as shown in FIG.

  Finally, as shown in FIG. 1 (f), a sample that can be observed with a transmission electron microscope can be obtained by milling from the observation side surface with an ion milling device to a thickness of several hundred to several tens of nm or less.

In this case, a fluoronitric silicon etching solution is used for etching the sample piece. However, it is obvious that the same effect can be obtained by a dry etching method using a gas such as CF ₄ .

  Moreover, in the best mode for carrying out the present invention, the case where a silicon substrate is used as a sample has been described as an example. However, the same photoresist process and etching process can be performed on other materials. It is clear that sample preparation is possible.

The figure which shows the sample preparation method of this invention. 1A is a perspective view showing a sample piece cut out from a silicon substrate, FIG. 1B is a perspective view showing a sample piece after surface polishing, and FIG. 1C is a sample piece on which a selective opening pattern is formed. 1 (d) is a cross-sectional view showing a sample piece after etching, FIG. 1 (e) is a cross-sectional view showing a sample piece from which a photoresist has been removed, and FIG. 1 (f) is a sample after ion milling. Sectional drawing which shows a piece. The figure which shows the sample preparation method by the conventional ion milling method. 2 (a) is a perspective view showing a sample piece cut out from a silicon substrate, FIG. 2 (b) is a perspective view showing a thinned sample piece, and FIG. 2 (c) is after processing by a bowl polishing machine or a dimple machine. FIG. 2D is a cross-sectional view showing the sample piece after ion milling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Observation surface 2 Sample piece 3 Photoresist 4 Etching part 5 Observation part

Claims (1)

  A method for preparing a sample for observation with a transmission electron microscope, wherein a pattern is formed with a photoresist on a substrate to be a sample, an etching process is performed only on a predetermined part, and an ion is applied to the part subjected to the etching process. And a step of polishing with a milling apparatus.

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