JPH04173957A - Formation of boron nitride film - Google Patents

Abstract

PURPOSE:To form a hard BN film excellent in heat conductivity and electrical insulating property by irradiating the surface of a substrate with the ion of B or a B compd. and the ion of N or an N compd. along with a rare gas or hydrogen gas with a specified ion energy. CONSTITUTION:A vacuum chamber 1 contg. an ion source 5 opposed to a substrate 3 such as an Si wafer is evacuated, the gaseous B or B2H6 and the gaseous N2 or N compd. are mixed with a rare gas such as Ar, and the mixture is supplied to the ion source 5 from a gas inlet pipe 6. The ion source 5 is then driven, the substrate 3 is irradiated with the mixed gas ions at the energy of 50-5000eV, and a high-hardness BN film contg. cubic BN and excellent in heat conductivity and electrical insulating property is formed on the surface of the substrate 3 with high adhesion.

Description

[Detailed description of the invention] <Public funds for industrial use> The present invention is directed to the formation of a boron nitride film, which is hard and contains crystal grains of boron nitride, particularly cubic boron nitride, and has excellent thermal conductivity and electrical insulation properties. Regarding the method.

<Conventional technology> Boron nitride can be roughly divided into two types: ■ Hexagonal boron nitride (hBN), which is easily synthesized at room temperature, is soft, and has excellent lubricity;
Cubic boron nitride (CBN) is synthesized at high temperature and high pressure, and is hard and has excellent thermal conductivity and electrical insulation. Among these, CBN has a hardness second only to diamond and has low reactivity. Known as an excellent wear-resistant material.

On the other hand, methods for synthesizing boron nitride as a film include chemical vapor deposition (CVD) and physical vapor deposition (PVD).
law). Here, in the CVD method, boron halides and diborane (B, H, This is a method of depositing. Furthermore, the PVD method is a method in which metallic boron is evaporated in nitrogen gas plasma and deposited on a base material.

<Problems to be Solved by the Invention> However, boron nitride films formed on substrates by conventional CVD or PVD methods do not contain cubic boron nitride crystal grains; The problem with this method is that a boron nitride film with high hardness cannot be obtained.

In view of these circumstances, an object of the present invention is to provide a method for forming a boron nitride film that contains cubic boron nitride in the film and is hard and has excellent thermal conductivity and electrical insulation.

Means for Solving the Problems> A method for forming a boron nitride film according to the present invention that achieves the above object comprises using gas ions of boron and/or a compound containing boron and gas ions of a compound containing nitrogen in a vacuum. , rare gas and/or hydrogen gas ions are irradiated onto the base material, and the energy of the ions at that time is set to 50 to 5000.
It is characterized by being eV.

<Action> Gas ions of boron and/or a compound containing boron,
When raw material gas ions consisting of nitrogen or gas ions of a compound containing nitrogen are irradiated onto the base material together with gas ions of a rare gas and/or hydrogen mainly for imparting energy,
Boron nitride mixed with cubic boron nitride or consisting of cubic boron nitride is deposited on the substrate. As a result, a hard boron nitride film with high surface smoothness, thermal conductivity, and electrical insulation properties is formed.

Example of implementation Hereinafter, the present invention will be explained based on examples.

First, an apparatus for carrying out this embodiment will be explained with reference to FIG. In the figure, l is a chamber capable of maintaining a vacuum, and its exhaust port IA communicates with a vacuum source (not shown). On the ceiling of chamber 1 is a substrate holder 2.
is attached, and a base material 3 is held below this base material holder 2, and this base material 3 is cooled by cooling water introduced via a cooling water supply/discharge pipe 4. There is. On the other hand, an ion source 5 is provided at the bottom of the chamber 1 so as to face the base material 3 . The ion source 5 is, for example, a microwave discharge type ion source with an ion beam diameter of about 100 m, and includes a gas introduction tube 6 to which gas is supplied. Then, from this gas introduction pipe 6, a gas of boron and/or a compound containing boron (hereinafter referred to as boron-based gas), a gas of nitrogen and/or a compound containing nitrogen (hereinafter referred to as nitrogen-based gas), and a rare gas are introduced. When a mixed gas consisting of gas and/or hydrogen gas is supplied, this mixed gas is ionized and is applied to the base material 3 as mixed ions 7 in a large area and with a large current.
It is irradiated towards.

Next, an example of forming a boron nitride film using such an apparatus will be described.

First, the base material 3 made of Si wafer was attached to the base material holder 2. Thereafter, the inside of the chamber 1 is communicated with a vacuum source (not shown) via the exhaust port IA, and the inside of the chamber 1 is
Preliminary exhaust was performed to -6 torr or higher. This degree of vacuum is usually 2
It is preferable to set the value to about X 10-5 torr or less, but it goes without saying that the value is not limited to such a value if, for example, N2 substitution is performed.

On the other hand, diborane (H, B,) gas as a boron-based gas, nitrogen gas as a nitriding gas, and argon gas as a rare gas were mixed with 15% by volume of diborane gas and 1% by volume of nitrogen gas.
The 1,7-on source 5 was driven by supplying gas through the gas introduction pipe 6 at a ratio of 5% by volume and 0% by volume of Albin gas. This results in
The base material 3 is irradiated with mixed ions 7 of 100 eV and 200 μA/- from the ion source 5, and boron nitride @S is deposited on the base material 3.
was formed to a thickness of about 1 μm.

Note that the degree of vacuum at this time was approximately I x 10''torr.

When the boron nitride film 8 thus formed was analyzed by infrared absorption spectrum analysis, absorption at wavelengths around 100 an', which is unique to cubic boron nitride, was observed; '
No nearby absorption was observed. Further, from the electron diffraction ring pattern obtained by an electron beam diffraction device, the boron nitride film 8 is
It was confirmed that the film was a polymorphic crystal film of cubic boron nitride.

Further, the hardness of the boron nitride film 8 was as high as 4800 kg/m<2 >with respect to a load of 10 g. Furthermore, when the surface roughness of the boron nitride film was measured, the JIS maximum height Rmax was estimated to be about 0.03 μm, and it was confirmed that the film surface had excellent smoothness.

In addition to the examples described above, a boron nitride film 8 was formed by varying the energy of the mixed ions 7, and its hardness was measured. The results are shown in FIG. As a result, when the ionization energy is in the range of 70 to 3000 eV, a boron nitride film consisting of crystal grains of cubic boron nitride can be obtained; It was confirmed that a boron nitride film containing hexagonal boron nitride crystal grains was obtained. Note that if the ion energy exceeds 5000 eV, the energy is too large and the formation of the boron nitride film itself does not occur, and if the ion energy is less than 50 eV, the proportion of cubic boron nitride is small and the hexagonal boron nitride film is not formed. The ratio becomes extremely high, making it impossible to achieve the object of the present invention, which is both undesirable.

In the above-mentioned embodiment, B2 residual gas was used as the boron-based gas, but other boron-based gases! =l, Tlf
, BCJ, BF, B5N5H, and the like. In addition to nitrogen gas, nitrogen-based gases include
Ammonia (NH, ) or the like can be used. Further, as the rare gas, in addition to argon gas, helium, neon, xenon, krypton, etc. can be used.

Note that hydrogen gas can be used together with or in place of the rare gas, but when hydrogen gas is used, it is thought that the chemical effect is greater than the effect of imparting energy.

Further, the degree of vacuum in the chamber 1 in which the method of the present invention is carried out is not particularly limited as long as the ion source 5 is activated and ions having a predetermined energy are irradiated.

Furthermore, in the present invention, a boundary layer in which base and film components are mixed is formed by irradiating ions with such high energy that the ions penetrate into the interior of the base material at the initial stage of film formation, and then, Forming a film has the effect of increasing the adhesion of the film to the base material.

As explained above, according to the method of the present invention, a boron nitride film containing cubic boron can be easily formed.

Furthermore, this method has the advantage that the coating can be formed only by ion irradiation, so the work efficiency is good, and since the ion beam has directivity, the layout of the apparatus can be freely designed.

<Effects of the Invention> As explained above, the present invention forms a film by irradiating ions of a mixed gas of boron-based gas, nitrogen-based gas, rare gas, and/or hydrogen with a predetermined energy. The present invention has the effect of forming a hard boron nitride film that is made of boron nitride or contains cubic boron nitride, and has excellent thermal conductivity and electrical insulation.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a film forming apparatus for carrying out this example, and FIG. 2 is a graph showing the results of the example. In the drawing, 1 is a chamber, 2 is a substrate holder, 3 is a substrate, 5 is an ion source, 6 is a gas introduction tube, 7 is a mixed ion, and 8 is a boron nitride film.

Claims (1)

[Claims] A base material is irradiated with boron and/or gas ions of a boron-containing compound, gas ions of a nitrogen-containing compound, and rare gas and/or hydrogen gas ions in a vacuum, and the energy of the ions at that time is A method for forming a boron nitride film, characterized in that the voltage is 50 to 5000 eV.