JPH04107258A - Production of thin boron nitride film - Google Patents

Abstract

PURPOSE:To form a thin film of high purity cubic boron nitride on a substrate by irradiating a target containing boron atoms with excimer laser light and also irradiating the surface of a substrate with nitride ions. CONSTITUTION:A target 4 is disposed and also a substrate 5 is disposed in a manner to be opposed to the target 4 in a film formation chamber 9. As the target 4, a simple substance of boron, a sintered compact of hexagonal boron nitride, a single crystal of cubic boron nitride, etc., are used. The distance L between the target 4 and the substrate 5 is kept at about 10-150mm, and the substrate 5 is heated to about 300-1300 deg.C by means of a heater 6. Laser light is emitted by means of an excimer laser device 1 and laser power density is increased by means of a condenser lens 2, and the surface of the target in the film formation chamber 9 is irradiated with the above laser light via an entrance window 3. Further, a nitride ion introducing nozzle 8 and an exhaust hole 7 are provided to the inside of the film formation chamber 9, and the surface of the substrate is irradiated with nitride ions through the nozzle 8. By this method, the high quality thin cubic boron nitride film can be stably obtained.

Description

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

[Conventional technology]

As methods for synthesizing cubic boron nitride (abbreviated as c-BN) from the gas phase, there are, for example, the following three known techniques.

(1), as described in Japanese Patent Application Laid-open No. 18626/1983, boron is evaporated onto a substrate from an evaporation source containing boron, and at least ion species containing nitrogen are deposited on the substrate from an ion source that generates ionic species. A method for producing cubic boron nitride, comprising irradiating ion species to produce a thin film of boron nitride on the substrate.

2. Method for producing cubic boron nitride on a substrate by chemically transporting boron using H, +N1 plasma [Reference 1: Coconut Materials Science Letters, Journal of
Materials 5science Lett
ers, 4 (1985) p, 51-54].

3. HCD (Hollow Cathode D)
While evaporating boron with a gun (polow cathode discharge), ionize N from the hollow electrode and irradiate the substrate, apply high frequency to the substrate to create a self-bias effect, and create cubic nitride on the substrate. Method for producing boron [Reference 2: Inagawa Gai, Bros. Deindusts on 9th Symposium on Ion Source Assisted Chikunoroshii, Proceedings
of 91h Symposium on Ion A
ssistedTechnology, '85.
Tokyo, p. 299-302 (1985)).

[Problem to be solved by the invention]

However, in any of the above methods, the equipment configuration is complicated and expensive, and at present, the boron nitride produced contains a large amount of hexagonal boron nitride (abbreviated as h-BN), which has excellent crystallinity. It is difficult to say that cubic boron nitride has been obtained.

The present invention eliminates the drawbacks of the conventional methods and provides a new method for producing and depositing a highly pure cubic boron nitride thin film on a substrate surface using a less expensive device.

[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 irradiates the surface of a substrate placed opposite to the target with nitrogen ions, thereby forming a cubic surface on the substrate. A method for forming a boron nitride thin film is provided, which is characterized by forming a crystalline boron nitride thin film.

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

FIG. 1 shows an example of an integrated structure of the present invention, in which a film forming chamber 9 is shown.
A target 4 and a substrate 5 are arranged in opposition to the target 4. As the target 4, a simple substance of boron, a sintered body of hexagonal boron nitride, a single crystal or polycrystalline body of cubic boron nitride, etc. are used. Target 4 and substrate 5
The distance 111L is kept within a range of 10 to 150 mm. The substrate 5 is heated to 300 to 1300'C by a heater 6. The excimer laser device 1 emits laser light, the condensing lens 2 increases the laser power density,
The surface of the target 4 in the film forming chamber 9 is irradiated through the incident window 3. Laser power is 0.5-20J/c
The range is m2. Furthermore, a nitrogen ion introduction nozzle 8 and an exhaust lower are provided in the film forming chamber 9, and the substrate surface is irradiated with nitrogen ions from the nozzle 8. The method for generating nitrogen ions is RF.

Methods that use plasma such as microwaves or methods that directly irradiate ions in the form of a beam are used. Film forming pressure is 10
-'~totorr. Such a technique makes it possible to create a cubic boron nitride thin film on a substrate.

[Effect]

The excimer laser has an oscillation wavelength in the ultraviolet region of 193 to 350 nm, ~F, KrαXeC1',
There are types such as XeF. In the present invention, the reason why these excimer lasers are used is that the energy of one photon is large. For example, ArF
In the case of an excimer laser, the oscillation wavelength is 193 nm, which corresponds to an energy of 6.42 eV.

On the other hand, in COI lasers, which are commonly used as industrial lasers other than excimer lasers, the oscillation wavelength power <1
0.6 um, which has an energy of at most 0.12 eV.

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

Furthermore, in the present invention, nitrogen ions play an extremely important role in the synthesis of cubic boron nitride. The present inventors believe that this is probably due to the nucleation itself of cubic boron nitride, or to the removal of hexagonal boron nitride and amorphous boron nitride that are generated during the synthesis of cubic boron nitride. is thinking.

The method of generating nitrogen ions in the present invention can be a method using plasma such as RF or microwave, or a method of directly irradiating ions in the form of a beam.

In the present invention, the energy and ion amount (density) of nitrogen ions to be irradiated depend on the ion introduction method and other film forming parameters, and desired values can be appropriately selected depending on the case. That is, regarding the energy, it is generally said that an energy of several keV or less is optimal for film formation in the case of an ion beam, whereas it is said to be about several to several tens of eV for ionization by plasma. The amount of ions should be appropriately selected so that the B/N ratio in the film approaches the stoichiometric ratio, that is, l·l.

The targets of the present invention include elemental boron, sintered bodies of hexagonal boron nitride, single crystals or polycrystals of cubic boron nitride, pyrrolitic boron nitride (abbreviated as p-BN), and wurtzian boron nitride (abbreviated as p-BN). (abbreviated as w-BN) etc. are used.

In the present invention, the reason why the laser power on the target surface is set to 0.5 to 20 J/c++'' is that if it is too low, the excitation of the target will be insufficient and the film growth rate will be low, while if it is too high, the clusters will form. This is because a large amount of oxidation occurs, making it impossible to form a good cubic boron nitride film.

In the present invention, the film forming pressure is appropriately selected depending on the method of irradiating the substrate with nitrogen ions. For example, when using a nitrogen ion beam, the degree of vacuum is as high as possible (10-' to 10't), taking into consideration the mean free path of the ions.
orr), and in the case of introducing a gas by plasma excitation, a relatively high pressure of about several torr is sufficient because ions can be sent into the chamber using a gas flow.

Note that the irradiation angle of the laser 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, the distance between the target and the substrate (L in FIG. 1) 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;
This is because if the value exceeds 1, it becomes difficult for excited species accompanied by light emission to reach the substrate, and the film forming rate becomes extremely low, which is not practical.

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 later, formation of cubic boron nitride was observed even at room temperature. However, in order to further improve crystallinity, it is necessary to heat the substrate to 300°C to 1300°C.

If the temperature is lower than 300° C., migration of particles arriving at the film growth surface will not be sufficient, resulting in an amorphous film.

If the temperature exceeds 1300° C., the cubic boron nitride film is often rearranged into a hexagonal boron nitride film, and the heat resistance of the substrate itself often becomes a problem, which is not practical.

The thickness of the cubic boron nitride film according to the present invention varies depending on the film formation time.

The substrate used in the present invention can be appropriately selected by the person concerned depending on the purpose, and is not particularly limited to, but may include blue, diamond, and M. , WC, etc. can be used as a substrate to synthesize a cubic boron nitride film.

〔Example〕

EXAMPLES The present invention will be specifically explained below using Examples, but the present invention is not limited thereto.

Using the apparatus shown in FIG. 1, a cubic boron nitride thin film was created using SI as a substrate. The obtained film thickness is 1000-200
Approximately 0 people. Table 1 shows the film formation conditions and X-ray diffraction results. Note that the distance between the target and the substrate is sample Nα20,
5mm, 50mm, 200 respectively at 21.22
In all cases, the city was set at 60. Furthermore, in Table 1, [UUU means [Microwave J].

In the margin table 1 below, Nα1-Illα5 is the laser power l'
The dependence was investigated, and a good cubic boron nitride thin film was obtained in the range of 0.5 to 20 J/cm.
~Nα11 is the material of the target, Nα15~Nα19
are different film-forming pressures, Nα20 to Nα2
2 was obtained by changing the distance, and Nα23 to Nα26 were obtained by changing the substrate temperature, and the peak of cubic boron nitride was observed even at room temperature due to N ion irradiation.

Although not specifically shown in the examples, in order to further enhance the effect of irradiating the film-forming surface with nitrogen ions, DC, A
A substrate bias such as C (RF) may also be used. If the substrate is insulating, the same effect can be obtained by making the substrate holder conductive and applying DC, AC, etc. to that part.

〔Effect of the invention〕

As explained above, the present invention uses an excimer laser to irradiate a target containing at least boron with the laser and irradiates the substrate surface with N ions, thereby producing a high-quality cubic boron nitride thin film. can be obtained stably.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing one embodiment of the present invention. In the figure, l is an excimer laser, 2 is a condenser lens, 3 is an entrance window,
4 is a target, 5 is a substrate, 6 is a heater, 7 is an exhaust port, 8 is a nitrogen ion introduction nozzle, and 9 is a film forming chamber.

Claims (1)

[Claims] A cubic boron nitride thin film is formed on the substrate by irradiating a target containing boron atoms with excimer laser light and irradiating the surface of the substrate facing the target with nitrogen ions. A method for creating a boron nitride thin film characterized by forming a film.