JPH06275575A - Formation of diamond thin film pattern - Google Patents

Abstract

PURPOSE:To precisely work a diamond thin film so as to manufacture a diamond device which operates at a high temperature by selectively etching the diamond thin film by plasma etching by using a mask. CONSTITUTION:A diamond thin film 2 is formed on the entire surface of a Si substrate 1, the surface 11 of which is scratched with diamond powder, by plasma CVD using reactive gases H2 and CH4. Then, after forming an SiO2 film 3 on the thin film 2 and the pattern of a resist film 4, the exposed parts of the film 3 are selectively etched by plasma etching and the resist film 4 is removed by soft-off. Thereafter, the parts of the thin film 2 which are not protected with the film 3 are selectively etched by performing ECR plasma etching using O2 plasma. Finally, the film 3 and the SiO2 film on the surface of the substrate 1 are removed with HF water. Thus the diamond thin film 2 can be precisely worked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a diamond thin film pattern, which is a technique required for manufacturing a semiconductor device capable of operating at high temperature.

[0002]

2. Description of the Related Art Diamond, which is a crystal material of carbon, is
Since each atom forms a covalent bond, it also has semiconductor properties. Its characteristic is that the bandgap is about five times wider than that of conventionally used Si, and therefore it is expected to be used as a material for devices that operate at high temperatures, which has been difficult until now. Diamonds
CH _4, CO, by activating the like plasma or thermal energy gas and mixed gas of H ₂ and the like CF _4, can be synthesized on a Si substrate scratched. The H ₂ gas at this time has a role of removing the graphite component formed at the same time as the diamond. In recent years, by mixing B ₂ H ₆ gas containing boron at the time of synthesis, B is added to diamond, which acts as an acceptor impurity, enabling the synthesis of diamond having P-type semiconductor properties. It was As a result, trial production of Schottky diodes, FETs, various sensors, etc. has recently been carried out using diamond having P-type semiconductor properties.

[0003]

However, when actually manufacturing a device, it is necessary to form a fine pattern of a diamond thin film. Conventionally, by utilizing the property that diamond grows only on a substrate that has been subjected to a scratch treatment, a selective scratch treatment is performed, or a film such as SiO ₂ is selectively synthesized on the scratched portion, Selective growth has taken place. However, in the case of selective growth, a diamond nucleus may be generated even on a slight scratch on the substrate, and an ultrathin film such as SiC may be formed on a scratch-free portion. SiO _{2 on the} damaged part
Even when a film such as SiO ₂ is synthesized, it is not possible
₂ Diamond may grow on the film. Therefore, it is difficult to form a fine pattern with the technique using selective growth.

In order to actually manufacture a device with diamond, fine processing technology is still indispensable, and how to achieve fine processing is an important issue. An object of the present invention is to provide a pattern forming method of a diamond thin film capable of fine processing required for producing a diamond device.

[0005]

In order to achieve the above object, the method for forming a diamond thin film pattern according to the present invention is to selectively etch a diamond thin film by using a mask. It is effective that the plasma etching is ECR plasma etching and that plasma of gas containing oxygen atoms is used for plasma etching.
Oxygen or water vapor is effective. In that case, it is effective that the mask is made of a silicon oxide film. It is also effective to use hydrogen plasma for plasma etching.

[0006]

It is known that diamond is damaged by oxygen plasma. This is because diamond has the property of easily reacting with oxygen at high temperatures. Based on this fact, it became possible to form a pattern by plasma etching of diamond. In addition to oxygen plasma, water vapor plasma or hydrogen plasma can be used for plasma etching. Therefore, a fine pattern can be formed using a mask manufactured by photolithography. In order to increase the etching rate, it is effective to raise the substrate temperature of the diamond thin film, and SiO ₂ is suitable as the material of the mask that can withstand such high temperature and oxygen plasma atmosphere.

[0007]

EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 (a) to 1 (h) which conceptually show the diamond thin film microfabrication process according to the present invention. Example 1 As a diamond film forming substrate, a Si substrate 1 whose surface 11 was scratched with diamond powder was used [FIG. 1 (a)]. A diamond thin film 2 having a film thickness of about 1 μm was formed on the entire surface of the substrate 1 by μ wave plasma CVD under the following conditions [FIG. 1 (b)].

[0008]

[Table 1] Next, a SiO ₂ film 3 having a thickness of about 0.5 μm was formed on the diamond thin film 2 by sputtering under the following conditions [FIG. 1 (c)].

[0009]

[Table 2] For patterning the SiO ₂ film, a pattern of the resist film 4 was formed by exposing and developing a photoresist [FIG. 1 (d)]. Next, the exposed SiO ₂ film 3 was selectively etched by plasma etching using CF ₄ as a reaction gas [FIG. 1 (e)]. Then, the resist film 4 was removed by lift-off [FIG. 1 (f)]. After that, the diamond thin film 2 not protected by the SiO ₂ film 3 was selectively etched by ECR plasma etching using O ₂ plasma under the following conditions [FIG. 1 (g)].

[0010]

[Table 3]Finally, HF + H₂O (1:20) solution for SiO₂Membrane 3 and
And the surface of the Si substrate 1 which is probably formed by the influence of plasma
Surface sio₂The film was removed [Fig. 1 (h)]. In this way
Diamond thin film 2 as in general semiconductor technology
It could be finely processed. ECR Plasma Etch
Substrate temperature during etching of diamond thin film by etching
Is possible at 100 ° C, but the etching rate is
Becomes faster as becomes higher. However, if the substrate temperature is high
When it ’s time to squeeze₂Mask is damaged, making fine processing difficult
Become. Example 2: Diamond thin film 2 shown in FIGS. 1 (a) and 1 (b)
Deposition process, SiO shown in Fig. 1 (c) ₂Membrane 3 deposition process implemented
Same as Example 1. After this, as in Example 1, the cash register
Pattern of strike film 4 is formed [Fig. 1 (d)], SiO₂Membrane power
Turning [Fig. 1 (e)], removal of the resist film 4 [Fig.
(f)] was performed. Diamond thin as shown in Fig. 1 (g) below
Selective etching of the exposed part of the film 2 is carried out by H in this embodiment.₂
Performed by ECR plasma etching using O plasma
It was. The etching conditions were as follows.

[0011]

[Table 4] When the substrate temperature is as low as 100 ° C, the etching is not promoted so much, indicating that temperature plays an important role in diamond etching. Then, the SiO ₂ film 3 was removed by etching in the same manner as in Example 1 to obtain the structure shown in FIG. 1 (h).

In the above embodiments, the etching was carried out by the plasma of the gas containing oxygen atoms, but the etching of the diamond can also be carried out by the plasma containing no oxygen atoms, for example, H ₂ plasma. Figure 2 shows O ₂ plasma,
The relationship between the substrate temperature and the etching rate in ECR plasma etching of a diamond thin film using H ₂ O plasma and H ₂ plasma is shown.

[0013]

According to the present invention, a chemically stable diamond thin film is microfabricated to form a pattern by plasma etching using a gas containing oxygen or plasma of hydrogen, and by using a SiO ₂ mask. can do. This made it possible to manufacture diamond devices that operate at high temperatures.

[Brief description of drawings]

FIG. 1 is a sectional view conceptually showing the steps of forming a diamond thin film pattern of one embodiment of the present invention in the order of (a) to (h).

FIG. 2 is a relationship diagram of substrate temperature and etching rate in various plasmas.

[Explanation of symbols]

1 Si substrate 2 Diamond thin film 3 SiO ₂ film 4 Resist film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoko Endo 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd.

Claims (7)

[Claims] 1. A pattern forming method for a diamond thin film, which comprises selectively etching by using a mask by plasma etching. 2. The method for forming a diamond thin film pattern according to claim 1, wherein the plasma etching is ECR plasma etching. 3. The pattern forming method for a diamond thin film according to claim 1, wherein plasma of a gas containing oxygen atoms is used for plasma etching. 4. The method for forming a diamond thin film pattern according to claim 3, wherein the gas containing oxygen atoms is oxygen. 5. The method for forming a diamond thin film pattern according to claim 3, wherein the gas containing oxygen gas is water vapor. 6. The method of forming a diamond thin film pattern according to claim 3, wherein the mask comprises a silicon oxide film. 7. The method of forming a diamond thin film pattern according to claim 1, wherein hydrogen plasma is used for plasma etching.