JPH03207864A - Production of cubic boron nitride - Google Patents

Abstract

PURPOSE:To produce c-BN by a CVD method by heating after glow plasma on an after glow plasma CVD system and also carrying out thermal activation by providing a thermion generator in the after glow plasma. CONSTITUTION:B2H6 and NH3 are introduced as reactant gases into a reaction cylinder 2 and a plasma produced from a high frequency coil 3 is allowed to act to produce an active intermediate product. An after glow plasma containing this intermediate product is heated by means of a heating furnace 4 to accelerate reaction. Further, in order to decompose the intermediate product, heating is performed by means of a W filament 5 to carry out thermal activation. By this method, c-BN can be produced by a CVD method capable of forming a film on a large area by means of a reaction with minimized residual stress.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention is directed to the production of cubic boron nitride (c-
BN). ``Prior Art'' Because c-BN is as hard as diamond, there has recently been much research into synthesizing c-BN using a gas phase method under reduced pressure. For example, Mr. Sato, a carpenter's examiner, reported that he succeeded in producing c-BN using a combination of ion irradiation and vacuum evaporation (Proceedings of the 33rd Applied Physics Association Conference 1986).
spring). However, this method requires ions accelerated by high voltage, and is considered unsuitable for industrialization. In addition, Ito et al. reported that c-BN could be synthesized by the HCD-ARE method in the above-mentioned manuscript, but the residual stress was large and films with a thickness of 5000 μm or more would peel off from the substrate. It has drawbacks and is not suitable for industrialization. In general, the CVD method is characterized by lower residual stress during film formation than the PVD method described above. but,
In the CVD method, hexagonal BN (h-BN) is synthesized and c-
BN has not been approved. "Problems to be Solved by the Invention" When forming a film of hexagonal BN (h-BN) using the conventional CVD method, it has the industrially advantageous feature of being able to form a film over a large area with low residual stress. There is. However, it has generally been the case that the synthesis of c-BN has not been achieved using the CVD method. As a BN film formation method using the CVD method, it is generally done to use B2Hs and NH3 as reaction gases and add plasma.
Only N is synthesized. The reason why h-BN is synthesized is thought to be that the BN polymer, which exists as an intermediate in the chemical reaction process, is deposited as is on the substrate. Therefore, the present inventors thought that in order to synthesize c-BN, it is necessary to decompose the BN polymer and give energy to a single BN molecule. "Means for Solving the Problems" The present invention is characterized in that the afterglow is heated by an afterglow plasma CVD method, and a thermionic generation device is provided during the afterglow to thermally activate the c-BN.
This is the manufacturing method. An example of a device used for uninvented invention is shown in the first example.
This will be explained using a diagram. The reaction gas is B2H. and NH3 are used, and the reaction gases are introduced into the reaction column 2 through an inlet pipe 1. The reaction tube 2 is made of quartz glass and can withstand high temperatures. A high-frequency coil 3 is provided on the outer periphery of the upper part of the reaction tube 2, thereby generating an inductively coupled plasma in the reaction tube z to excite the reaction gas and form an active intermediate. A heating furnace 4 is provided at the lower outer periphery of the reaction 1v12, thereby heating the afterglobe plasma containing the active intermediate to promote the reaction. A W filament 5 as a thermionic generator is provided on the inner periphery of the lower part of the reaction tube 2, and by applying a voltage to it through an electrode 6, thermionic electrons are generated and the intermediate polymer can be further decomposed. ing. In addition, a sample holder 7 is provided at the bottom of the reaction tube 2, on which a substrate is placed. "Operation" Using the device described in the above means, a reaction gas is introduced into the reaction tube 2, excited by the high frequency coil 3 to produce an active intermediate, and heated in the heating furnace 4. This accelerated the reaction. The afterglow plasma containing the intermediate was heated with a rough W filament 5 to thermally activate it. Through the above steps, c-BN was obtained on the substrate surface. Furthermore, since h-BN was obtained when the W filament was not energized or thermally activated, it was confirmed that the inventors' idea was valid. "Example" Using the apparatus shown in Fig. 1, a reaction gas is introduced into the reaction tube z, and the plasma generated from the high frequency coil 3 is applied to the reaction gas to generate an active intermediate. The afterglobe plasma containing the body was heated in a heating furnace 4 to accelerate the reaction (CVD method). In order to further decompose the intermediate, a film of c-BN was formed on the substrate by heating with a W filament 5 (thermal activation). For comparison, a film was also formed on the substrate without thermal activation using the W filament 5. The conditions for the above membrane process are as follows. I%B2H6 (H2 dilution) and 1%NHff (H2
(diluted), and the film was formed for 90 minutes at a reaction pressure of ITorr. Si (10G) was used as the substrate that was placed on the sample holder 7 provided in the reaction tube z to form a film on its surface. The input power to the high-frequency coil 3 that generates inductively coupled plasma was set to IOOW, and the temperature at which the afterglow was heated in the heating furnace 4 was fixed at 800°C. The heating temperature of the W filament 5 is 2000℃ every 200℃ from 800℃.
The structure of the BN film formed on the substrate was identified using electron diffraction and infrared absorption spectroscopy, and the identification results are shown in Table 1. An example of electron beam diffraction of the thermally activated film is shown in Figure 2 (^), and its lattice constant was a, = 3.B2A, and it was identified as c-BN. An example of electron diffraction of a film that does not undergo any activation is shown in Figure 2 (B), and its lattice constants are a, = 2.50λ, c0 = 6.66λ, and it can be identified as h-BN. In addition, the membrane was thermally activated.
The infrared absorption spectra of the films without thermal activation are shown in Figure 3. In Figure 3, when thermal activation is performed, h- around 1380 cm-' and around 800 cm-'
Absorption by BN disappears, and c around 1100 cm-'
The fact that -BN is absorbed indicates that C -BN can be obtained by thermal activation. From Table 1, the temperature of the W filament is 1 for c-BN film formation.
This is a case of 400°C to 2000°C, and it can be seen that there was a thermal activation effect in that temperature range. Note that in this example, W
Although thermal activation was achieved by heating with a filament, it is also possible to use other thermionic generators instead. "Effects of the Invention" According to the present invention, c-BN can be produced using the CVD method, which was previously impossible.
This makes it possible to manufacture films, and the residual stress during film formation can be reduced, which has a great effect on industrialization.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the apparatus used in the present invention, Figure 2 is a diffraction diagram obtained by electron beam diffraction of a film formed using the same apparatus, and Figure 3 is an infrared absorption spectrum diagram of a film formed in the same manner. be.

Claims (2)

[Claims] (1) B_2H_6 and NH as reaction gases in the reaction column
_3 and apply plasma to the reaction gas,
A method for producing cubic boron nitride, which comprises forming an active intermediate, heating an afterglow plasma containing this intermediate to promote the reaction, and further heating with a thermionic generator. (2) The temperature at which the intermediate is heated by the thermionic generator is 1
The method for manufacturing cubic boron nitride according to claim 1, wherein the temperature is 400 to 2000°C.