JPH09133618A - Apparatus and method for manufacture of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an apparatus which can manufacture a thin-film sample which does not comprise any ion damage layer and which is suitable for a high-resolution observation operation and an EDX analysis in the manufacturing method and the manufacturing apparatus, of the thin-film sample which can be observed under a transmission electron microscope, which make use of an ion polishing method. SOLUTION: A sample 5a which is coarsely ground to a prescribed thickness in advance is held in a vacuum, one face of both faces of the sample 5a are irradiated with an ion beam which is converged on a very small region, a prescribed part and its peripheral part are changed into a thin film, the spray of a chemical grinding liquid 9 is jetted to the part and to its peripheral part in their places so as to be chemically ground. In this way, a thin film, for observation under a transmission electron microscope, which does not comprise any ion damage layer and which is suitable for a high-resolution observation operation and an EDX analysis is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film manufacturing apparatus and a thin film manufacturing method capable of manufacturing a thin film applicable to transmission electron microscope observation.

[0002]

2. Description of the Related Art A transmission electron microscope (hereinafter referred to as a transmission electron microscope).
The observation of the material structure by using the is conventionally performed as one means of material evaluation. However, in observing with a transmission electron microscope, the sample is 0.1 to 0 so that the electron beam can be transmitted. ．
It is necessary to reduce the thickness to about 3 μm. In order to reduce the thickness of a sample, an electropolishing method is generally used for a metal material, and an ion polishing method is mainly used for a semiconductor or ceramic because there is no suitable electrolytic solution. However, recently, even in the case of a metal material, when observing the cross-sectional structure of a material having a multi-layered structure, etc., the ion polishing method is often used because an appropriate electrolytic polishing liquid or electrolytic polishing rate varies depending on the layer. .

In the ion polishing method, an ion beam having a diameter of several mm is often used. Further, a focused ion beam (FIB) process using an ion beam of 0.1 μm or less is also used to form a thin film for observing a cross section. Is being used for. For example, JP-A-5-231997
In the publication, after a polymer film is formed on the entire sample, focused ion beam processing and chemical treatment using hydrofluoric acid are sequentially used to leave an observation site as a thin film wall. A sample preparation method for observing the shape has been proposed. However, in the ion polishing method, since the acceleration voltage of the ions is usually about 5 kV, the ions are implanted into the sample, and an amorphous ion damage layer is formed on the surface layer of the sample. In the FIB processing in which the acceleration voltage is as high as about 30 kV as compared with the ion polishing method, the ion damage layer is deep. In case of ion polishing method, about 10n
An ion damage layer having a thickness of about m is known.

The presence of such an ion-damaged layer causes deterioration of image quality during high-resolution observation with a transmission electron microscope, and ion implantation during elemental analysis by energy dispersive X-ray analysis (EDX analysis). Has appeared in the analysis spectrum. The chemical polishing method has been conventionally used for metal materials,
It is often applicable to semiconductor materials. However, in the case of a semiconductor material, it is generally fragile, and when it is formed into a thin film of 1 μm or less, it is often broken during handling. For this reason,
It is necessary to devise a technique such as sealing paraffin around the observation area. Further, Japanese Patent Application Laid-Open No. 7-43277 proposes a device equipped with a device capable of holding an etching solution for preparing a thin film sample. However, in any case, the chemical polishing method has a complicated process, there is a possibility that impurities may be mixed, and it requires a high degree of skill such as selection of a polishing liquid and polishing conditions according to the material.

With the technical development of transmission electron microscopes, high resolution and ancillary equipment for analysis and the like have come to have sophisticated capabilities. In such a situation, the preparation of the observation sample is becoming more important. There has been a demand for a sample preparation method that matches the development of such observation and analysis instruments.

[0006]

The present invention advantageously solves the above problems, can be applied to any material, and is capable of producing a thin film sample suitable for high resolution observation and EDX analysis without an ion damage layer. And to provide a method.

[0007]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, the chemical polishing method is particularly effective for removing the ion-damaged layer. The present invention has been constructed by discovering that it is effective to perform the chemical polishing only in a local region for microscopic observation and further to perform the chemical polishing in the same place as the ion polishing.

The present invention is a thin film forming apparatus comprising a vacuum container, an ion polishing apparatus and a chemical polishing apparatus, wherein the ion polishing apparatus is provided with a sample holder in the vacuum container and a holder relative to the sample holder. Ion gun installed in the position to
An extractor / accelerator electrode installed between the ion gun and the holder, or an ion beam focusing device and a deflecting device is further provided, and the chemical polishing device is installed outside the vacuum container. And a nozzle provided in the vacuum container so as to spray the chemical holding liquid on the sample held by the sample holder, and the tank and the nozzle are connected via a pipe. The thin film forming apparatus is characterized in that a flow control valve is provided in the pipe, and the present invention holds a sample that has been roughly ground to a predetermined thickness or less in advance in a vacuum, An ion damage layer characterized by performing chemical polishing by irradiating the sample with an ion beam to thin a predetermined portion and its peripheral portion, and then immediately injecting a chemical polishing liquid vapor to the portion and its peripheral portion. Without Film, which is a method for manufacturing a.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The thin film forming apparatus of the present invention comprises a vacuum container, an ion polishing apparatus, and a chemical polishing apparatus. 1 and 2 schematically show an embodiment of the present invention. The vacuum container 1 is maintained at a predetermined vacuum degree by an exhaust device (not shown). The degree of vacuum during polishing is preferably about 10 ⁻³ Pa or less.

The sample holder 5 holds a thin film material, and it is preferable that the ion irradiation angle of the sample can be arbitrarily changed. The ion gun 2 is for generating an ion beam, and one ion gun 2 is sufficient, but when polishing both surfaces of the sample at the same time, it is desirable to install one pair with the sample sandwiched therebetween. The form of the ion gun is not particularly limited, but the discharge type using an inert gas such as Ar is simple.
The generated ion beam is accelerated by the extraction / acceleration electrode 3 and irradiated on the sample. Acceleration voltage is 2kV-10kV,
The ion current is preferably 0.2 mA to 1.0 mA from the viewpoint of polishing rate and ion damage. The angle of incidence of the ion beam can be freely selected, but considering the polishing rate, it is preferably 5 to 30 degrees.

In FIB processing, the acceleration voltage is 20
The kV to 50 kV and the ionic current are preferably 1 μA to 3 μA. Although the ion source is not particularly limited, it is possible to obtain a sufficient ion current density even when the ion beam is focused.
Liquid metal ion sources such as a are preferred. Furthermore, FIB
In processing, generally, a sample surface is scanned and irradiated with an ion beam focused from a vertical direction, so that a focusing device 4 and a deflecting device 4a are required as shown in FIG. And so on, 0.1
It can be controlled to scan a beam of ˜2 μmφ in an arbitrary region. Further, in the FIB processing, the secondary electron image generated by the ion beam irradiation can be observed by the secondary electron detector, and the sample holder 5 has a positioning mechanism so that the processing position can be arbitrarily determined.

The chemical polishing liquid is determined by the material to be polished, is supplied from the chemical polishing liquid storage tank 9 installed outside the system of the vacuum container through the pipe 6, and is supplied from the nozzle 7 to the sample 5a.
Is injected as steam into. The injection can be performed from one side or both sides. It is important that the chemical polishing be performed at the same place immediately after the ion polishing is completed in order to minimize polishing other than the observation position.

Although the shape of the nozzle 7 is not particularly specified, it is necessary that the nozzle 7 is not easily corroded by the polishing liquid, and a hole shape having a spray area corresponding to the size of the observation area may be selected.
The spray is preferably atomized. Furthermore, it is desirable that the nozzle be placed outside the path of the ion beam during ion polishing and have a moving mechanism that moves to the vicinity of the sample only during chemical polishing.

It is desirable to install a pair of nozzles so that both surfaces of the sample can be polished at the same time, but the number of nozzles is not limited to one, and one nozzle may be used to polish each surface. The flow rate of the chemical polishing solution vapor is determined by the material of the sample to be polished and the concentration of the polishing solution, and is controlled by the flow rate control valve 8 arranged in the middle of the pipe. Further, the injection time can be changed in consideration of the type of material and the polishing condition. When the material is single crystal silicon, when a 10 vol% hydrofluoric acid aqueous solution is used as the polishing liquid, 1 min is usually suitable at a flow rate of 10 ⁻⁴ ml / min. Since the injection is into a vacuum container, even if the opening of the valve is slight, it is sprayed in a spray form by opening the valve, and local polishing becomes possible. By spraying in the vicinity of the sample in the form of a spray, and without spraying the sample with a nozzle having a narrow hole diameter, the sample is sprayed at that position, so that it is possible to polish only at a desired site and a necessary site and its narrow periphery. In this way, chemical polishing can accurately remove the ion damage layer generated by ion polishing.

In the present invention, the sample is preliminarily polished by preliminary polishing such as mechanical polishing, and has a predetermined thickness or less, preferably 50 μm.
It is preferable to keep m or less. Thereby, the load of ion polishing can be reduced.

[0016]

【Example】

Example 1 A thin piece cut out from a single crystal silicon wafer was used to prepare a thin film using the apparatus shown in FIG. About 20μ after mechanical polishing and concave polishing from a single crystal silicon wafer
After having a thickness of m, ion polishing was performed. Ion polishing was performed under the conditions of an acceleration voltage of 5 kV, an ion current of 0.5 mA, an ion beam incident angle of 20 °, and a vacuum degree of 10 ⁻³ Pa. Subsequently, the same region that was ion-polished was treated with a 10 vol% hydrofluoric acid aqueous solution at a flow rate of 10 ⁻⁴ ml / min from the nozzle 7 for 1 mi.
Chemical spray was performed by spraying for n. Also, as a comparative example, a thin film only by ion polishing was prepared. As a result of observing the thin film thus obtained with a transmission electron microscope, no significant difference is observed in the electron microscope images, but in the electron beam diffraction pattern of the comparative example, a halo pattern showing the presence of an amorphous layer is observed. However, it is not recognized in the examples of the present invention. An EDX spectrum was obtained in a region where the thickness was estimated to be 50 nm or less. FIG.
In the example of the present invention obtained from the thin film subjected to the ion polishing and the chemical polishing shown in (a), only the peak of Si is recognized, whereas in the comparative example of only ion polishing (FIG. 3B), S
An Ar peak is observed in addition to the i peak. Thus, the ion damage layer can be removed by using the apparatus of the present invention to produce a thin film for transmission electron microscopy by the method of the present invention.

(Example 2) A thin film of an Al ₂ O ₃ film formed on a Fe-Cr-Al alloy was prepared by the apparatus shown in FIG. The Al ₂ O ₃ coating was micro-cuttered to give
After being cut to a thickness of 5 mm, it was mechanically polished to a thickness of about 50 μm in the cross-sectional direction, and then FIB processing was performed by the apparatus of the present invention shown in FIG. FIB processing, acceleration voltage 3
A focused ion beam of Ga ions of 0 kV, an ion current of 2 μA and a beam diameter of 2 to 0.1 μm is used, and the degree of vacuum is 10 ⁻³ P.
It carried out on condition of a. Subsequently, the same ion-polished region was treated with a 10 vol% hydrofluoric acid solution at a flow rate of 10 ⁻⁴ ml / mi.
No. n, chemical spraying was performed by spraying from the nozzle 7 for 10 minutes. Also, as a comparative example, a thin film only by ion polishing was prepared. As a result of observing the thin film thus obtained with a transmission electron microscope, a halo pattern showing the presence of an amorphous layer is observed in the electron beam diffraction pattern of the comparative example, whereas it is not observed in the example of the present invention. An EDX spectrum was obtained in a region where the thickness was estimated to be 100 nm or less. In the example of the present invention shown in FIG. 4 (a), only the peaks of Al and O and the peaks of Fe and Cr which are alloy components are observed, whereas in the comparative example of only ion polishing (FIG. 4 (b)), Ga peaks are observed in addition to Al and O, Fe and Cr peaks. As described above, it is understood that the ion damage layer is removed by producing a thin film for a transmission electron microscope by the method of the present invention using the apparatus of the present invention.

[0018]

According to the present invention, the ion damage layer formed during ion polishing can be removed, and it becomes possible to prepare a thin film sample most suitable for high resolution observation and EDX analysis. Furthermore, the risk of sample breakage during sample handling is reduced, and the workability of sample preparation is greatly improved. Further, by selecting the chemical polishing liquid, it is possible to apply to a wider variety of materials.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a thin film sample preparation device in one example of the present invention.

FIG. 2 is a schematic view showing a thin film sample preparation device in one example of the present invention.

FIG. 3 Energy dispersive X of single crystal silicon wafer
It is a figure which shows a line diffraction pattern. (A) is for ion polishing + chemical polishing, and (b) is for ion polishing only.

FIG. 4 is a diagram showing an energy dispersive X-ray diffraction pattern from an Al ₂ O ₃ coating. (A) is for ion polishing + chemical polishing, and (b) is for ion polishing only.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Ion gun 3 Extraction / acceleration electrode 4 Focusing device 4a Deflection device 5 Sample holder 5a Sample 6 Piping 7 Nozzle 8 Flow control valve 9 Chemical polishing liquid storage tank

Claims (2)

[Claims] 1. A thin film forming apparatus comprising a vacuum container, an ion polishing device and a chemical polishing device, wherein the ion polishing device is installed in the vacuum container at a position opposite to the sample holder. And an ion beam focusing device and a deflecting device provided between the ion gun and the holder, or an ion beam focusing device and a deflecting device. A chemical polishing liquid storage tank installed outside the vacuum container, and a nozzle provided inside the vacuum container so as to spray the chemical polishing liquid on the sample held by the sample holder, the tank and the nozzle being A thin film forming apparatus, which is connected through a pipe and is provided with a flow rate control valve in the pipe. 2. A sample preliminarily rough-polished to a predetermined thickness or less is held in a vacuum, and the sample is irradiated with an ion beam to thin a predetermined portion and its peripheral portion, and immediately thereafter, the portion and its portion. A method for producing a thin film having no ion damage layer, which comprises performing chemical polishing by spraying a chemical polishing liquid vapor to the peripheral portion.