JPH04119982A - Production of boron nitride film - Google Patents

Abstract

PURPOSE:To form a high-purity cubic boron nitride thin film on the surface of a substrate with an inexpensive device by providing a heated filament between a target contg. B and the substrate opposed to the target. CONSTITUTION:A target contg. boron atom is irradiated with an excimer laser beam to synthesize a cubic boron nitride film on a substrate opposed to the target in a gaseous atmosphere contg. nitrogen atom as follows. Namely, a heated filament is provided between the target and substrate. Although the laser beam power on the target surface depends on the distance between the target and substrate, etc., the power is appropriately controlled to 0.5-20 J/cm<2>. When the power is too low with respect to the range, the target is insufficiently excited, and the film growth rate is decreased. Meanwhile, when the power is too high, many clusters are formed, and an excellent cubic boron nitride film is not formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a cubic boron nitride film used for cemented carbide tools, insulating films, semiconductors, and the like.

[Conventional technology]

As a method for synthesizing cubic boron nitride (hereinafter also referred to as c-BN) from the gas phase, there are, for example, the following three known techniques.

■ Depositing boron onto a substrate from an evaporation source containing boron, as described in JP-A No. 60-181626, and at the same time depositing ionic species containing at least nitrogen onto the substrate from an ion generating source that generates ionic species containing nitrogen. A method for producing a cubic boron nitride film, which comprises irradiating the substrate with boron nitride to produce boron nitride on the substrate.

■ A method for producing cubic boron nitride on a substrate by chemically transporting boron using us + N* plasma [Reference 1: Comat et al., Journal of Materials Science Letters, Journal of
Materials 5science Letter
s, 4 (1985) p, 51-54].

■ HCD (lollow Cathode Di
While evaporating boron with a charge (hollow cathode discharge) gun, ionize N from the hollow electrode and irradiate the substrate, apply high frequency to the substrate to create a self-bias effect, and deposit boron nitride on the substrate. How to generate [Reference 2: Inagawa et al.
9th Symposium on Ion Source Assisted Technology, Proceedings of
9th Symposium on Ion As5
istedTechnol.

gy+'s5. Tokyo, p. 299-302 (198
5)].

[Problem to be solved by the invention]

However, method (2) has the disadvantage that the ion beam generator is expensive. Since the method (2) uses high-power RF plasma for film formation, it has the disadvantage that impurities from the reaction system are likely to be mixed in. Said■
Like method (2), method (2) has the drawback that the ion beam generator and focusing device are expensive, and in addition, atoms of the inert gas are incorporated into the deposited boron nitride film.

In addition, in any of the above methods, it is difficult to say that cubic boron nitride with excellent crystallinity can be obtained at present. In other words, with the conventional manufacturing method, a single-phase film consisting only of c-BN cannot be obtained, but a hexagonal boron nitride (hereinafter referred to as h-BN) film.
It is a film containing BN (also called BN).

The purpose of the present invention is to overcome the drawbacks of such conventional methods and provide a novel method for producing a boron nitride film that can generate and deposit a highly pure cubic boron nitride thin film on the surface of a substrate using less expensive equipment. shall be.

[Means to solve the problem]

As a means to solve the above problems, the present invention irradiates a target containing boron atoms with excimer laser light and synthesizes a cubic boron nitride film on a substrate placed facing the target in a gas atmosphere containing nitrogen atoms. In the method of
The present invention provides a method for manufacturing a boron nitride film, characterized in that a heated filament is provided between the target and the substrate.

In the present invention, supplying a gas containing hydrogen and/or fluorine atoms between the target and the substrate can be cited as a particularly preferred embodiment of the present invention.

Furthermore, it is a particularly preferred embodiment of the present invention that the target contains hydrogen atoms and/or fluorine atoms.

Hereinafter, the present invention will be described in detail based on the drawings. FIG. 1 shows a specific example of the present invention, in which a target 3 is placed on a target holder 2 in a film-forming channel 1, and a substrate 5 is placed on a substrate holder 4 opposite to this. There is. Target 3 includes simple boron, hexagonal boron nitride (h-BN), pyrolytic BN (also called p-BN), single crystal or polycrystalline C-BN, B H*
, Nlb, lb B Os, etc. are used. A heated filament 12 made of W (tungsten) or the like is placed between the target 3 and the base 5 . The substrate 5 is heated to 300°C to 1300°C by the heater 6 or the filament 12. Furthermore, in the film forming chamber 1, N1)-
Gases containing N atoms such as,! A gas containing hydrogen or fluorine, such as No. 13, F8, or CF4, is introduced from the gas supply device 7. Further, if necessary, a method of generating plasma by applying a voltage from a DC, RF, microwave power source 8 or the like to generate a discharge may be used. Film forming pressure is 1O-6~10
Torr. A laser beam is emitted by an excimer laser device 9, the laser power density is increased by a condenser lens 10, and the surface of the target 3 in the film forming chamber 1 is irradiated through the entrance window 1). Laser power is 0!
The range is 5 J/cm' to 20 J/cm'. Such a method makes it possible to manufacture a c-BN film.

[Effect]

Excimer laser has an oscillation wavelength in the ultraviolet region of 193 nm to 350 nm, and is RF.

There are types such as KrC1, XeCe, and XeF. In the present invention, the reason why these excimer lasers are used is that the energy of one photon is large. For example, if it is an ArF excimer laser,
The oscillation wavelength is 193 nm, which corresponds to an energy of 6.42 eV. On the other hand, CO! is commonly used as an industrial laser other than excimer laser! For lasers, the oscillation wavelength is 106 μm, which is at most 0.1 μm.
It has only 2 eV of energy.

Second, since laser light can be focused using an optical system such as a lens, the energy density can be further increased. Such high-energy laser irradiation decomposes the target and generates excited species (bloom) that emit light. ) is produced, making it possible to synthesize boron nitride.

However, the boron nitride film obtained in this way is
This results in a c-BH film containing BN and having poor crystallinity.

A heated filament is provided between the target and the substrate,
By supplying a gas containing hydrogen and/or fluorine atoms, or by irradiating a target containing hydrogen atoms and/or fluorine atoms with laser light and exposing the vaporized substance to a filament, hydrogen atoms, fluorine atoms, or HF Radicals are generated. These products play a vital role in the synthesis of high quality c-BN. Perhaps h is synthesized simultaneously during c-BN synthesis.
The inventors believe that this is effective in removing -BH by etching, nucleation of cubic boron nitride itself, or correcting the deviation from the stoichiometric ratio of the c-BH film to be synthesized. . By applying a negative bias (DC or RF self-bias) to the substrate or substrate holder, the role of raising becomes more pronounced.

In the present invention, the laser power on the target surface varies depending on the distance between the target and the substrate, etc.
5 J/cm' to 20 J/crn2 is suitable.

If the power is lower than the above range, the excitation of the target will be insufficient and the film growth rate will be low. On the other hand, if the temperature is too high, many clusters will occur, making it impossible to form a good cubic boron nitride film.

In the present invention, the film forming pressure is appropriately selected depending on other manufacturing conditions, but it is difficult to form a discharge at a pressure less than IO-bTorr or more than 10 Torr.

The temperature of the filament in the present invention is 1700'c~
2300°C is preferred. If the temperature is lower than 1700°C, few hydrogen atoms are produced and the effect of the present invention is small. 2300℃
There are few materials that can withstand higher temperatures, and filament constituent elements are mixed into the film as impurities due to filament evaporation, making it impractical. The distance between the filament and the substrate is preferably 5 mm to 30 mm.

The angle of irradiation of the laser onto the target is not particularly limited, but according to studies by the present inventors, a suitable angle is 45°±20° with respect to the target surface.

In the present invention, Targera!・Distance between and the board (first
(in the figure) is also important as a film-forming parameter. Although it depends on other film forming parameters, it is usually kept at 10 to 150 mm. The reason for this is that if the thickness is less than 10 mm, the film formation rate will be too high and the amount of B in the film will increase;
If it exceeds m, it becomes difficult for the excited species accompanied by luminescence to reach the substrate.
Furthermore, the film formation rate becomes extremely low, making it impractical.

In the present invention, these laser power, film forming pressure, and distance between the target and the substrate are mutually related to control the gas phase reaction, and desired values can be selected.

Substrate temperature is an important parameter for crystal formation.

In the present invention, as shown in Examples described below, formation of a film containing c-BN crystals was observed even at room temperature. but,
For further crystallinity improvement, 300°C to 1300°C
It is preferable to heat the substrate. If the temperature is lower than 300° C., the migration of particles arriving at the film growth surface will not be sufficient and the amorphous component will increase. If the temperature exceeds 1300°C, the hexagonal crystal component increases, and the heat resistance of the substrate itself often becomes a problem, making it impractical.

The substrate used as a base in the present invention can be appropriately selected by the person concerned depending on the purpose, and is not particularly limited, but includes Sl, diamond, and Mo.

A cubic boron nitride film can be synthesized using a WC2 iron-based material, ceramics such as Si, N4, etc. as a substrate.

〔Example〕

The present invention will be specifically explained below with reference to examples, but the present invention is not limited thereto. was prepared under the following manufacturing conditions.Table 1 shows the film forming conditions and
As a result of line diffraction ((1,1,1,) half-width of the diffraction peak - 20 angle), the c-
BN/h - BN peak ratio, and results of film composition analysis are shown.

Manufacturing conditions Excimer laser: kF (193 nm) Laser power: 2J/c Target: p-BN, BlbBtls,
B gas: N1, N IIs, lb, F, CF
4 Equal gas pressure + l OmTorr Substrate: SI Target-substrate distance L: 45 mm Substrate temperature 26
50°C Filament material: W-Re (none in Comparative Example 1) Filament temperature: 1850°C Substrate-filament distance: 10 mm Note that the filament was not heated in the apparatus shown in Figure 1, and the other conditions were the same. The example is Comparative Example 1, and the results are also shown in Table-1.

In addition, as Comparative Example 2, the IVD method (Ion VaporDepo
sition method Boron is evaporated onto the substrate from an evaporation source containing diboron, and ion species are irradiated onto the substrate from an ion generation source that generates ion species containing at least nitrogen to form boron nitride on the substrate. In the film production method, the ion acceleration energy of the ion species is set to 5 to 100 KeV per atom of the ion species, and the deposition and irradiation are performed in an atmosphere of nitrogen atoms or nitrogen compounds activated to a lower energy level than the ion species. A boron nitride film was prototyped and evaluated in the same manner as in Example 1 under the following conditions.

This result is also shown Shown in ■.

Manufacturing conditions Evaporation source: B (boron) metal N, acceleration energy: 15 KeV N, atmospheric pressure 4 X 10-' Torr substrate:
Sl Substrate temperature: 400°C or less Margin C From the results in Table 1, it can be seen that according to the present invention, there is no h-BN component, the half width of the X-diffraction peak is small, the half width is small, the crystallinity is good, and the stoichiometric ratio is high. It can clearly be seen that a quality c-BN film is obtained.

〔Effect of the invention〕

As explained above, in the present invention, excimer laser light is focused on a target containing boron atoms, and a cubic boron nitride film is formed on a substrate placed facing the target in a gas atmosphere containing nitrogen atoms. In the synthesis method, a high quality cubic boron nitride thin film can be stably obtained by a novel means of providing a heated filament between the target and the substrate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention. In the figure, 1 is a film forming chamber, 2 is a target holder, 3 is a target, 4 is a substrate holder, 5 is a substrate, 6 is a heater, 7 is a gas supply device, 8 is an RF or DC, 9 is an excimer laser, and IO is a collector. In the optical lens, 1) is an entrance window, and 12 is a filament.

Claims (3)

[Claims] (1) In a method of irradiating a target containing boron atoms with excimer laser light and synthesizing a cubic boron nitride film on a substrate placed facing the target in a gas atmosphere containing nitrogen atoms, the target and the substrate are A method for producing a boron nitride film, comprising providing a heated filament between the nitride film and the nitride film. (2) Hydrogen and/or
The method for manufacturing a boron nitride film according to claim 1, further comprising supplying a gas containing fluorine atoms. (3) Claim (1) or (2), wherein the target contains hydrogen atoms and/or fluorine atoms.
A method of manufacturing the boron nitride film described above.