JP2761026B2 - Method for manufacturing boron nitride film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the formation of a hard boron nitride film containing crystal grains of boron nitride, particularly cubic boron nitride, and having excellent thermal conductivity and electrical insulation. It is about the method.

[Conventional technology]

Boron nitride is roughly classified into soft, highly lubricated hexagonal boron nitride (hBN), which is easily synthesized at normal pressure, and hard, thermally conductive, and electrically insulating, which are synthesized at high pressure and high temperature. It is divided into cubic boron nitride (CBN).

 Separate methods for producing boron nitride films include chemical vapor deposition (CVD) and physical vapor deposition (PVD).

In the CVD method, a boride and nitrogen or ammonia, such as boron halide or diborane (B ₂ H ₆ ), are decomposed and activated by means of thermal excitation or the like in a chamber, and this is activated on the substrate. This is a method of depositing on the surface.

The PVD method is a method in which metallic boron is evaporated in a nitrogen gas plasma and deposited on a substrate.

[Problems to be Solved by the Invention] In both the conventional CVD method and the PVD method, cubic boron nitride crystal grains are not contained in the film of the boron nitride film formed on the base material.

Therefore, the conventional method has a problem that a boron nitride film having high hardness cannot be obtained.

The present invention has been made in view of the above situation, and includes a method of forming a boron nitride film containing cubic boron nitride crystal grains in a film, having high hardness, excellent thermal conductivity, and excellent electrical insulation. It is intended to provide.

[Means for solving the problem]

The method for forming the boron nitride film of the present invention is as follows.

(1) A mixed gas of nitrogen and a rare gas is supplied into a vacuum chamber.

(2) The mixed gas of nitrogen and the rare gas is ionized by an appropriate ionizing means to generate mixed ions.

(3) At the same time as depositing boron on the substrate, the substrate is irradiated with mixed ions of nitrogen and a rare gas to deposit boron nitride on the substrate.

Also, a mixed gas of nitrogen and a rare gas is
One feature is that the volume% is set.

Note that, as the rare gas, argon, krypton, or the like can be used.

[Action]

According to the method of the present invention, by simultaneously irradiating the substrate with mixed ions of nitrogen and a rare gas, it becomes possible to mix cubic boron nitride particles in boron nitride deposited on the substrate surface, It is possible to easily form a hard boron nitride film having a high thermal conductivity and electrical insulation.

 The surface of the film is also extremely smooth.

〔Example〕

Hereinafter, the method of the present invention will be described in more detail using the apparatus shown in the drawings.

In the figure, reference numeral 1 denotes a chamber capable of holding a vacuum, which communicates with a vacuum source (not shown) from an exhaust port 1A. Reference numeral 2 denotes a substrate holder, which is attached from the ceiling of the chamber 1 and is cooled by cooling water introduced and passed through the cooling water supply / discharge pipe 2A, thereby cooling the substrate 3 attached to the holder.

The ion source 4 is, for example, a microwave discharge type ion source. The ion source 4 ionizes a mixed gas of nitrogen and a rare gas supplied from a gas introduction pipe 6 and converts the mixed ions 7 into a large area and a large current to the base material 3. Irradiation toward.

The evaporation source 5 is, for example, an electron beam evaporation source, which is located immediately below the substrate holder 2 and has a metal boron 8 or the like as an evaporation material, and a boron vapor 9 evaporated from the evaporation source 9 on the substrate 3. This is for vapor deposition.

Reference numeral 10 denotes a monitor for measuring the amount of boron vapor 9 deposited on the substrate 3.

A method for forming a boron nitride film in an apparatus having such a configuration will be described below.

First, the substrate 3 made of a Si wafer is mounted on the substrate holder 2.

Next, the inside of the chamber 1 is communicated with a vacuum source (not shown),
The chamber 1 is pre-evacuated to 2 × 10 ⁻⁶ torr or less.

The metal boron 8 is evaporated from the evaporation source 5, and the nitrogen and the rare gas supplied to the ion source 4 are ionized to irradiate the mixed ions 7 to the substrate 3 to form a boron nitride film 11 on the surface of the substrate 3. I do.

The degree of vacuum at this time is about 1 × 10 ⁻⁴ torr.

In the formation of the boron nitride film 11, an argon gas is used as a rare gas, and a mixture ratio with nitrogen is set to 36% by volume of nitrogen and supplied from a gas introduction pipe 6, and the ion source 4 is driven to be discharged from the ion source 4. Mixed ion (0.5 KeV, 14 mA) 7
Is irradiated onto the base material 3 and, at the same time, a boron vapor 9 of metallic boron 8 is generated from the evaporation source 5 at a deposition rate of 0.4Å / S.
A 1.2 μm-thick boron nitride film 11 was formed on the substrate 3.

As a result of analyzing the boron nitride film thus obtained by infrared absorption spectrum analysis, absorption at a wavelength of around 1100 cm ^-1 specific to cubic boron nitride is recognized, but 1400 cm ^-1 specific to hexagonal boron nitride, And absorption around 800 cm ^-1 was not observed.

In addition, it was also confirmed from an electron diffraction ring pattern by an electron diffraction apparatus that the film was a polycrystalline film of cubic boron nitride.

The hardness is 4800 kg / Vickers hardness for a load of 10 g.
mm ² showed high hardness. Furthermore, a result of measuring the surface roughness of the boron nitride film, JIS maximum height is estimated to be about R _max = 0.02 [mu] m, it was confirmed that the excellent smoothness of the membrane surface.

In addition to the above experimental examples, various experiments were performed by changing the ratio of the mixed gas of nitrogen and argon gas. as a result,
When the volume percentage of nitrogen is in the range of 30 to 40, a film composed of cubic boron nitride grains is obtained, and in the other range of 20 to 90, cubic boron nitride and hexagonal boron nitride grains are mixed It was confirmed that a film was formed.

If the proportion of nitrogen exceeds 90% by volume, the proportion of cubic boron nitride is small, and the proportion of hexagonal boron nitride is extremely large, which does not meet the purpose of the present invention. No formation of the film itself occurred.

In addition, the energy of the mixed ions 7 was also varied. If the ion energy is less than 0.3 KeV, a boron nitride film will not be formed.On the other hand, if the ion energy exceeds 10 KeV, the film formed by sputtering will have many defects, and the deposition rate will be significantly reduced, resulting in a good quality boron nitride film. Could not be obtained.

Further, helium, neon, xenon, krypton and the like were used as a rare gas in addition to argon, but formation of a boron nitride film was confirmed.

〔The invention's effect〕

As described above, according to the method for forming a boron nitride film according to the present invention, it is possible to extremely easily form a boron nitride film having high hardness, thermal conductivity, and excellent electrical insulation containing cubic boron nitride crystal grains. can do.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings illustrate one embodiment of an apparatus that embodies the method of the present invention. 1: chamber, 2: substrate holder, 3: substrate, 4: ion source, 5: evaporation source, 6: gas inlet tube, 7: mixed ion, 8: metallic boron, 9: boron vapor, 10: monitor, 11: Boron nitride film

Claims (2)

(57) [Claims] 1. A mixed gas of nitrogen and a rare gas is supplied in a vacuum, and the deposition of boron and the irradiation of a mixed ion of nitrogen and a rare gas generated by an ion source are simultaneously performed on a substrate. A method for forming a boron nitride film. 2. The method for forming a boron nitride film according to claim 1, wherein the mixed gas of nitrogen and a rare gas contains nitrogen in a range of 20 to 90%.