JP2000199735A - Metal cutting method and method for preparing cross section sample for microscopic observation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a technique for preparing rapidly a cross section sample preventing the generation of burrs to the utmost at precise cutting of a soft metal material and capable of rapidly introducing a cross section sample into an FIB device. SOLUTION: An adhesive is applied to the surface to be observed of a material (a), which is a cross section sample for microscopic observation, and this coated material (a) is bonded to a material (dummy material) (b) same to the material (a) or having hardness which is about the same as that of the material (a) (i). Thereafter, the material (a) and the dummy material (b) are bonded under pressure and dried to form a sandwich-like structure (ii). Next, the sandwich structure is cut by a general-purpose precise cutter using a diamond blade, corresponding to a soft material to form a short strip-like cut piece (iii). After cutting, the cut piece is immersed in a solvent to dissolve the adhesive to have the surface of the sample exposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal cutting method for avoiding generation of burrs at the time of cutting a soft metal material, and a sample for observing a metal cross section for the purpose of observation with a transmission electron microscope (TEM). It relates to a manufacturing method.

[0002]

2. Description of the Related Art Recently, Focused Ion B
eam, hereinafter referred to as "FIB")
It has become relatively easy to prepare a cross-sectional sample for TEM observation, which has been difficult with the conventional method or has relied heavily on know-how. For example, JP-A-6-231719 describes the principle of this FIB processing apparatus and a processing method using the same. Also, Japanese Patent Application Laid-Open No. 7-318468 introduces a special shape processing by FIB processing to reduce a problem at the time of elemental analysis in an electron microscope. However, in order to realize these processes, high cutting accuracy is required at the time of cutting which is a pre-process.

[0003] FIB processing, which has been developed in the semiconductor field,
It is common to process a sample pretreated by a precision cutting device such as a dicing saw, and various devices have been devised for this cutting method. For example, a typical cutting method is introduced in JP-A-5-180739.

[0004]

On the other hand, not only in the field of semiconductors but also in the field of metal materials, preparation of cross-sectional TEM samples using a FIB processing apparatus has been studied. The possibility of sample preparation is expanding. However, it has been found that when the FIB processing method is applied to a metal material, precision cutting as a pre-treatment is not as easy as a semiconductor material.

At present, in the field of semiconductors, rapid pretreatment has been realized in which a sample is cut out with a width of several tens μm or less, and is directly introduced into an FIB apparatus. On the other hand, in the case of a soft metal material in particular, burrs may be generated at the time of cutting and cover the surface of the observation target. That is, when a soft cold-rolled steel sheet for automobiles or the like is cut by a general-purpose precision cutting device having a diamond blade for cutting metal, burrs are generated, and the burrs cover important sample surfaces. Although the degree of burrs depends on the material, the burrs may be deposited by several microns from the outermost surface, and the blade material may be mixed into the deposit. Further, when such a section is directly introduced into an FIB processing apparatus or the like and subjected to a normal process, not only does the thinning of the observation area be significantly delayed, but also the final purpose, a cross-sectional structure analysis using a microscope or the like, is often performed. It leads to having problems.

For this reason, in the case of a soft metal material, it is common to apply a FIB process after processing a relatively thick cut sample by hand polishing or the like, which is a major obstacle in speeding up sample preparation. Has become.

[0007] For example, Japanese Patent Application Laid-Open No. 9-141557 discloses a cutting grindstone using CBN abrasive grains in order to reduce burrs generated during cutting. However, the application range of the present invention in terms of cutting accuracy and the like is described. Is very different. Optimization of the type of diamond blade to be used and the cutting conditions are also being studied, but in many cases, these are counter to rapid processing.
At present, precision cutting as in the field of semiconductors has not been realized in the field of soft metals. As a result, the preparation of a sample for cross-sectional observation by the FIB processing apparatus still requires a complicated pretreatment step.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and when a soft metal material is precisely cut, it is possible to prevent the occurrence of burrs as much as possible and to quickly introduce it into an FIB device or the like. It is an object to provide a sample preparation technique.

[0009]

A first means for solving the above-mentioned problem is a method for cutting a soft metal material having a high frequency of occurrence of burrs, wherein the surface of the material to be cut is the same as the material to be cut. By bonding the surfaces of the material or materials having the same degree of hardness to each other via an adhesive layer, forming a sandwich structure, cutting, and then removing the adhesive layer. This is a characteristic metal cutting method (claim 1).

When soft metals such as Al and mild steel are cut, burrs are generated to varying degrees. This is because shavings are pushed out from the side surface of the blade to the sample surface when the blade used for cutting pushes the sample, and is a phenomenon that cannot be avoided with a metal having high ductility and malleability.

As a result of intensive studies conducted by the inventors on such problems caused by materials, the pretreatment is performed so that the target sample surface is not the outermost surface at the time of cutting. I had the idea that it was possible to completely avoid surface burrs.

For this purpose, the surface of the object may be coated in advance, and the surface may be exposed again after cutting. That is,
The same material as the sample or another material having the same hardness is pressed on the surface of the target sample via an appropriate adhesive layer. At this time, the adhesive layer is desirably as thin as possible and has the same hardness as the sample in consideration of the subsequent cutting step. With such a sandwich structure, the target surface is not the outermost surface at the time of cutting. After such a pretreatment, the sample is cut by a general-purpose precision cutting device, and immersed in an appropriate solvent to remove the adhesive layer, whereby a clean sample surface without burrs can be obtained.

[0013] A second means for solving the above-mentioned problems is as follows.
A method for preparing a cross-sectional sample for microscopic observation, comprising a step of cutting out a strip-shaped sample by the first means, and processing the slice so that it can be observed with a microscope. It is.

Since the observing surface of the strip-shaped sample cut by the first means has no burrs, it is introduced as it is into an FIB apparatus or the like as it is, and is processed so as to enable microscopic observation. As a result, a cross-sectional sample for microscopic observation can be produced more quickly than in the conventional method.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. First, apply an adhesive to the surface to be observed of the material (a), which is a cross-sectional sample for microscopic observation, and apply it to a material (dummy material) (b) that is the same as or harder than the material (a). Match (i). A person having ordinary skill in the art can determine, by a simple experiment, up to which hardness difference the material can be used as the dummy material (b). Thereafter, the material (a) and the dummy material (b) are pressed and dried to form a sandwich-like structure (ii).

As a pretreatment so that the surface of the target sample does not become the outermost surface at the time of cutting, a bonding method using an adhesive that is dissolved with an appropriate solvent is most preferable in consideration of exposing the surface of the target sample again after cutting. it is conceivable that. The adhesive is desirably an acrylic one that dissolves in acetone or the like, but is not limited to this as long as the adhesive can dissolve the material and the dummy material.

Next, the sandwich structure is cut by a general-purpose precision cutting device or the like using a diamond blade compatible with a soft material to produce a strip having a thickness of about 100 μm (iii). As the precision cutting device, a known device can be used. However, in consideration of introduction into a FIB processing device or the like, a processing accuracy of a degree used in the semiconductor field is essential. After cutting, the section is immersed in a solvent to dissolve the adhesive and expose the surface of the sample (iv). The slice with the surface of the target sample exposed is mounted on an appropriate holder and introduced into an FIB processing device or the like, and can be finished into a sample whose cross section can be observed with an electron microscope or the like.

[0018]

FIG. 2 shows a strip-shaped sample collected from a sandwich structure by a treatment according to the embodiment shown in FIG. 1 and immersion in a solvent to remove an adhesive layer. This is an example observed. An acrylic adhesive was used for bonding, and acetone was used for the solvent. On the other hand, FIG. 3 shows the target sample surface after a normal cutting step without covering the target sample surface. As is clear from these, remarkable burr generation is recognized in the conventional cutting method, whereas a clean surface without burrs is obtained in the cutting method of the present invention.

[0019]

As described above, according to the present invention, generation of burrs at the time of precision cutting of a soft material, which has conventionally been a problem, can be completely avoided. Further, by simplifying the pretreatment step that has been manually performed in preparing a metal cross-sectional TEM sample, it is possible to greatly speed up the preparation of a cross-sectional observation sample using an FIB processing apparatus or the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of the present invention.

FIG. 2 is a drawing substitute photograph showing an example in which the surface of a sample cut by the method of the present invention is observed with a scanning electron microscope (SEM).

FIG. 3 is a drawing substitute photograph showing an example in which the surface of a sample cut by a conventional method is observed with a scanning electron microscope (SEM).

Claims (2)

[Claims] 1. A method for cutting a soft metal material having a high frequency of occurrence of burrs, wherein a surface of a material to be cut and a surface of a material having the same hardness as that of the material to be cut or an adhesive layer are formed. A method for cutting a metal, comprising a step of forming a sandwich structure by bonding together, cutting the structure, and thereafter removing the adhesive layer. 2. A microscope observation method comprising a step of cutting out a strip-shaped sample by the metal cutting method according to claim 1, and processing the section so that the section can be observed with a microscope. For preparing cross-sectional specimens.