JP2636856B2 - Method for producing diamond thin film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a diamond thin film by a hot filament CVD method among gas phase synthesis methods.

(Prior art)

Conventionally, a diamond thin film is formed by a gas phase synthesis method, and the gas phase synthesis method is roughly classified into the following three methods. In other words, chemical vapor phase synthesis (CVD)… pyrolysis CVD, hot filament CVD, plasma CVD… R
F plasma CVD, microwave CVD, ion beam evaporation, etc.

However, in these conventional vapor-phase synthesis methods, in order to form diamond with good crystallinity, it is necessary to raise the substrate temperature to 700 ° C. or higher. In addition to the problem of becoming a carbon film, there is a problem that even if a diamond thin film is formed, the deposition rate is low.

On the other hand, when diamond thin films are applied to semiconductors and electronic devices, such as high-temperature operating transistors, semiconductor lasers, and high power devices, it is essential that the film be formed at a relatively low temperature of at least 600 ° C. or less. Met.

〔Purpose〕

An object of the present invention is to provide a method for producing a diamond thin film having excellent crystallinity at a relatively low temperature at a high deposition rate, which can be applied to the field of semiconductors and electronic devices.

〔Constitution〕

The present inventors have conducted intensive studies in order to achieve the above object, and as a result, a hydrocarbon gas or a hydrocarbon gas was formed by a hot filament disposed near a substrate in a vacuum vessel of 10 ^-3 to 10 ^-1 Torr.
Decompose a source gas consisting of a mixed gas of at least one organic compound gas containing a CH ₃ group and hydrogen gas, and deposit N ₂ and / or He on the substrate surface when depositing a diamond thin film on the substrate. It has been found that low-temperature film formation is possible by irradiating charged energy particles, and the deposition rate is remarkably increased. Thus, the present invention has been completed.

 Hereinafter, the present invention will be described in more detail with reference to examples.

FIG. 1 shows an example of an apparatus used for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a chamber, in which a susceptor 2 is provided, on which a substrate 3 is mounted. The substrate 3 is heated by the heat supply from the susceptor 2 and is kept at 250 to 850C, preferably 300 to 700C during the reaction. Therefore, as the substrate 3, not only a metal plate such as W, Mo, and Ta but also an inorganic material such as a Si wafer, SiC, and quartz glass can be appropriately used. The source gas is inserted from above the chamber 1 and supplied from a gas introduction pipe 6 opening above the substrate 3, and a heating element 4 (hot filament) arranged between the tip of the gas introduction pipe 6 and the substrate 3. To generate active species effective for film formation. As a raw material gas, a mixed gas of a hydrocarbon gas or an organic compound gas containing a CH ₃ group and a hydrogen gas is used. Specifically, examples of the hydrocarbon gas include saturated hydrocarbons such as methane, ethane, propane and butane; unsaturated hydrocarbons such as ethylene, propylene, acetylene and butadiene; and aromatics such as cyclopropane, cyclohexane, cyclobutadiene, benzene and toluene. Any of the group hydrocarbons may be used. The organic compound gas may be any of alcohols such as methyl alcohol, ethyl alcohol and isopropanol, ketones such as acetone, and ethers such as isopropyl ether and diethyl ether. These carbon compounds may be used in combination of two or more. The mixing ratio between the carbon compound and the hydrogen gas is such that the value of (carbon compound gas) / (hydrogen gas + carbon compound gas) is in the range of 0.1 to 10% by volume, preferably 0.5 to 5% by volume. Hydrogen gas in such a source gas generates atomic H by thermal decomposition, and active species effective for removing graphite as a by-product and forming a diamond film, for example, CH ₃ radicals, CH ₃ ion substrate 3 It appears to help move on the surface. As the heating element 4, a wire or boat of a metal heating element such as W, Mo, Ta, Kanthal, or a rod of a ceramic heating element such as SiC or C can be suitably used, and usually 1800 to 2300 ° C., preferably 1900 ° C. Heated to ~ 2100 ° C. Further, charged energy particles composed of an inert gas of N ₂ and / or He are irradiated from the ion source 5 toward the substrate 3 at an energy of several tens to several thousand eV and at an amount of several tens to several hundreds mA / cm ^2. Irradiation.

In such a device, the inside of the chamber 1 is 10 ⁻³ to 10
^{When the} film is formed at ^-1 Torr and the source gas is flowed from tens to hundreds of SCCM, the substrate 3 is required to obtain a high quality diamond thin film without irradiating the charged energy particles from the ion source.
Temperature must be at least 850 ° C or higher, but when the charged energy particles are irradiated, the diamond thin film has good crystallinity even when the substrate temperature is 250 to 850 ° C, preferably 300 to 700 ° C. was gotten. In addition, when irradiation with charged energy particles was performed, the deposition rate of the diamond thin film showed a relatively large value of 150 to 400Å / min. The results of Raman spectrum and electron diffraction of the obtained thin film are shown in FIG. 2 and Table 1.

From the results shown in FIG. 2 and Table 1, it is understood that the thin film obtained by the present invention is a diamond thin film having substantially the same configuration as natural diamond.

In the present invention, the reason for the low-temperature film formation and the improvement of the deposition rate by the irradiation of the charged energy particles from the ion source is that the irradiated charged energy particles collide with the active species on the substrate surface and increase the excited state of the active species. It is also thought that the substrate surface (reaction surface) is energetically excited to promote the migration of active species on the surface.

〔effect〕

According to the present invention as described above, a diamond thin film having good crystallinity can be formed at a low temperature, so that the diamond thin film can be applied to semiconductors and electronic devices, and can be deposited at a high speed, thereby improving efficiency. This has the effect that a good diamond thin film can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of an apparatus for carrying out the present invention. FIG. 2 is a Raman spectrum diagram of a thin film obtained according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Chamber 2 ... Susceptor 3 ... Substrate 4 ... Heating body 5 ... Ion source 6 ... Gas introduction pipe

Claims (1)

(57) [Claims] A mixed gas of at least one of a hydrocarbon gas or an organic compound gas containing a CH ₃ group and a hydrogen gas by a hot filament disposed near a substrate in a vacuum vessel of 10 ^-3 to 10 ^-1 Torr. A method for producing a diamond thin film, comprising decomposing a raw material gas and irradiating the substrate surface with charged energy particles comprising N ₂ and / or He when depositing the diamond thin film on the substrate.