JPH059513B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a boron nitride film (hereinafter, boron nitride is abbreviated as BN) that achieves high hardness using laser light. [Industrial Application Fields] BN includes cubic boron nitride (hereinafter abbreviated as CBN), hexagonal close-packed boron nitride (hereinafter abbreviated as WBN), and hexagonal boron nitride (hereinafter abbreviated as HBN).
Among these, CBN and WBN are attracting attention for a variety of wide-ranging applications due to their excellent thermal shock resistance, thermal conductivity, hardness and wear resistance, as well as resistance to iron group metals at high temperatures. As a result, methods for producing high-quality CBN and WBN are being researched. [Prior art] There is a known manufacturing method that uses expensive equipment and can be synthesized under several atmospheric pressures and extremely high temperatures of several thousand degrees Celsius. Research is being conducted on the efficient synthesis of CBN and WBN on the surface of substrates to produce thin films of them. [Problems to be solved by the invention] Synthesis of CBN and WBN by plasma CVD method, reactive ion plating method, etc. has not yet been reported, and recently, relatively high quality CBN has been produced by ionization synthesis method. There are only reports that a film of or WBN could be synthesized. Incidentally, according to this ionization synthesis method, boron is evaporated onto the substrate by electron bombardment, and at the same time, by irradiation with nitrogen ions,
A film of CBN or WBN can be formed on this substrate. [Means for Solving the Problem] In developing a new vapor phase growth method suitable for the synthesis of CBN and WBN in addition to the previously proposed ionization synthesis method, the present inventor conducted extensive research and found that the electron cyclotron We have discovered that a highly hard BN film can be formed by using resonance-excited plasma and supplying energy by projecting laser light into the plasma. The present invention was completed based on the above findings, and its purpose is to provide a novel method for producing a high-hardness BN film that efficiently synthesizes CBN and WBN films. Another object of the present invention is to provide a method for further improving hardness characteristics by promoting the production of CBN and WBN, and for forming a highly hard BN film on a substrate at a high film formation rate. According to the present invention, a BN generating gas is introduced into a reaction chamber in which a substrate is installed, and plasma is generated inside the reaction chamber to generate BN on the surface of the substrate by chemical vapor deposition. The present invention provides a method for producing a highly hard BN film, characterized in that a laser beam is projected into the plasma inside the reaction chamber so as to promote the bonding of boron atoms and nitrogen atoms. The present invention will be explained in detail below. In the present invention, a BN film is formed using an electron cyclotron resonance discharge device shown in FIG. It is characterized by the fact that it supplies energy. In FIG. 1, an electromagnetic coil 2 is placed outside the reaction chamber 1 to apply a magnetic field inside the reaction chamber 1, and microwaves (2.45 GHzHz) are introduced into the reaction chamber 1 via a waveguide 3. . According to this device, when using nitrogen atom-containing gas and boron atom-containing gas as the BN generating gas, nitrogen atom-containing gases such as N ₂ and NH ₃ (hereinafter abbreviated as N-containing gas) are introduced into the first introduction pipe. 4 into the reaction chamber 1, electron cyclotron resonance occurs, and the electrons collide with the N-containing gas and discharge, generating plasma. Then, as an ion accelerating voltage is applied to this plasma, the electrons enter the reaction chamber 1. 5, an ion beam is formed and irradiated onto the substrate 7 placed on the sample stage 6, and at the same time, ion beams such as B ₂ H ₆ , (C ₂ H ₅ ) ₃ B, BCl ₃ , BBr _{3 ,} etc. Boron atom-containing gas (hereinafter abbreviated as B-containing gas)
is ejected through a second introduction pipe 8 provided in a part of the precipitation chamber 5, CBN and WBN are released into this substrate 7.
is grown in a vapor phase on top of the During this vapor phase growth, laser light 10 having a predetermined wavelength range is introduced from the laser light source 9 into the precipitation chamber 5 through the laser light introduction window 11, and the plasma atmosphere is irradiated with this laser light 10. It is preferable to scan the surface of the base 7 by reflecting the light by a reflection plate 12 having a scanning function. That is, the cyclotron frequency of the electron is =
eB/2πm (where m: mass of electron, e: charge of electron, B: magnetic flux density) causes cyclotron motion, and when this frequency matches the frequency of microwave (2.45GHz), resonance occurs. As a result, electrons collide with molecules, ions, and radicals of the N-containing gas, and the highly excited state discharge phenomenon increases significantly, further increasing the ionization rate in the plasma. Because of the high plasma ion density, the gas pressure can be set at 10 ^-3 to 10 ^-5 torr, which allows for a significantly lower pressure than the ionization synthesis method, resulting in high purity plasma with high ion density. occurs. In the present invention, the plasma generated in the reaction chamber 1 as described above is turned into an ion beam in the deposition chamber 5 and is made to collide with the substrate 7 installed on the sample stage 6, while at the same time supplying B-containing gas to the substrate at a predetermined flow rate. It is important to eject it towards 7. In other words, by applying a bias voltage to the ion accelerating electrode 13,
An ion accelerating voltage is applied to the plasma, and the ion accelerating electrode 13 includes a ground electrode 14 provided on the inner wall of the reaction chamber 1, a porous electrode that partitions the reaction chamber 1 and the precipitation chamber 5, and serves as a place for emitting the ion beam. It is composed of a bias electrode 15 of
It is recommended to apply within the range of 5000V. If this bias voltage is less than 50V, the nitrogen source necessary for the generation of CBN and WBN will be insufficient, and the characteristics of CBN and WBN will be reduced in the BN film formed on the substrate.
If it exceeds 100%, the film formation rate decreases and production efficiency deteriorates. Therefore, this bias voltage is 50 to 5000V,
Preferably it is 200 to 1000V. Then, as positive ions of the plasma are irradiated with an ion beam onto the substrate 7, the nitrogen source for CBN/WBN generation becomes high energy and collides with the substrate 7, and at the same time, the B-containing gas flows into the second introduction pipe 8. through the base 7
When ejected, N atoms and B atoms become highly excited states with SP ³ hybrid orbitals, respectively, in order to synthesize CBN and WBN. In order to efficiently synthesize CBN and WBN from N atoms and B atoms having such SP ³ hybrid orbitals, it is necessary to introduce N into each of the reaction chamber 1 and the precipitation chamber 5.
N contained in each of the containing gas and B-containing gas
It is important to specify the atomic ratio of N atoms and B atoms, and it is preferable to set the atomic ratio of N atoms to B atoms in the range of 1/10 to 10. If it deviates from this setting range, precipitation may occur. During,
The content of CBN and WBN is considerably reduced. It has been experimentally confirmed that this optimum condition is in the range of 1/2 to 3. It is necessary that the temperature of the substrate 7 is maintained within a predetermined range during the precipitation of BN. This allows the CBN and WBN grown in a vapor phase to adhere to the substrate 7 while maintaining their structure, and to form a film. can be developed. The substrate temperature is preferably -100 to 500℃, and if it is outside this range, it will become amorphous and hexagonal.
As the number of BN increases, high-quality products consisting of CBN and WBN
Since a BN film cannot be obtained, the temperature is preferably 0 to 250°C. Incidentally, 16 is an outlet for exhaust gas that is no longer needed for the production of CBN or WBN. Furthermore, in the present invention, it is important to project a laser beam having a predetermined wavelength range into the plasma atmosphere in order to efficiently synthesize CBN and WBN from N atoms and B atoms having SP ³ hybrid orbitals as described above. It is. That is, the inventor has determined that the wavelength range of this laser light is
It was found that when the thickness is set within the range of 7.5 to 12 μm, BN formed at a high film formation rate exhibits remarkable high hardness properties. It is desirable to irradiate the laser beam toward the base 7 as much as possible. Such a wavelength range is shown in Figure 2 by CBN and
It can be seen that this corresponds to the absorption peak of the infrared absorption spectrum of WBN. Therefore, this laser light is N
It is thought that it serves as a source of bonding energy between atoms and B atoms, and promotes the bonding reaction. This BN bonding reaction can be explained as follows using Figure 3. a indicates the unbonded energy potential of B atoms and N atoms with SP ³ hybrid orbitals, and when activation energy E ^* ₁ is supplied by laser light irradiation, CBN exceeds the energy potential X.
energy potential b that brings about
It becomes a BN bond. However, if an inappropriate activation energy E ^* ₂ is supplied, it is thought that the energy potential c will exceed the energy potential Y and result in HBN. In other words, in order for N atoms and B atoms to combine to form CBN or WBN, it is necessary to overcome the activation energy barrier of E ^* ₁ . However, with conventional excitation methods, such as heating and plasma ionization, all degrees of freedom of the reactant molecules, that is, translational motion and internal energy levels, are uniformly excited and the reaction occurs. In addition to WBN generation, HBN generation also occurs. On the other hand, when a laser beam with good monochromaticity is used, it is possible to select the level at which the molecule is excited, so it becomes possible to directly excite the internal energy level of the molecule with the optical energy of the laser beam. Therefore, it is necessary to irradiate a laser beam having a wavelength range of 7.5 to 12 μm, which corresponds to the activation energy E ^* ₁ , and the present inventor believes that the optimal wavelength range of laser light is 9 to
It was confirmed through experiments that the thickness was 10 μm. In the present invention, as the laser beam mentioned above,
Anything with a wavelength range of 7.5 to 12 μm can be used, such as CO ₂ gas laser,
HF gas laser, also PbSnTe, PbSnSe,
There are semiconductor lasers such as HgCdTe, PbSnSeTe, and PbSnSSe. [Effects of the Invention] Thus, according to the method for producing a highly hard BN film according to the present invention, while setting the N atoms contained in the N-containing gas to a predetermined atomic ratio, the gas is caused to collide with electrons by electron cyclotron resonance. to discharge the
As a result, high-purity plasma is efficiently generated, an ion beam with a large beam diameter is formed from this plasma, and high-energy positive ions are irradiated onto the temperature-set substrate, and at the same time, B atoms in a predetermined range are emitted. A highly hard BN film made of CBN or WBN is formed at a high film formation rate by blowing out the B-containing gas contained in the substrate and irradiating it with a laser beam having a predetermined wavelength range. Furthermore, since the substrate is heated by ion beam irradiation, not only is there no need for a heat source to heat the substrate, but also a heat source for plasma generation such as a filament is not used, so defects in such heat sources may cause problems in the production of high-hardness BN films. It also has the advantage that formation is not inhibited and stable production can be maintained, and as a result, we were able to provide a method for producing a highly reliable high-hardness BN film that is suitable for mass production. Next, embodiments of the present invention will be described. Example 1 Using the above-described electron cyclotron resonance discharge device, N ₂ gas was first introduced into the reaction chamber 1 through the first introduction pipe 4 at a flow rate of 0.1 ml/min. As a result, the pressure inside the reaction chamber 1 is always set at 10 ^-4 torr, a magnetic field is applied inside the reaction chamber 1 by the electromagnetic coil 2, and a microwave (2.45 GHz)
is introduced into the reaction chamber 1 via the waveguide 3 to generate electron cyclotron resonance plasma. Then,
When a bias voltage of 900 V is applied to the ion accelerating electrode 13, an ion beam is formed, and the ion beam is irradiated onto the silicon substrate 7. At the same time, B ₂ H ₆ gas is introduced from the second introduction tube 8 at a flow rate of 0.05 ml/min.
was introduced into the precipitation chamber 5. In this case, the atomic ratio of N atoms to B atoms is 2. Furthermore, a laser beam with a wavelength of 9.6 μm is emitted from a laser light source 9 consisting of a CO ₂ gas laser to a reflector plate 12 with an output power as shown in Table 1, and while the reflector plate 12 is operated for scanning, the substrate is The laser beam was scanned over the surface of 7. When the thus obtained BN film was analyzed by X-ray diffraction, peaks that could be identified as CBN (111) and WBN (002) were confirmed, and their existence was confirmed. The film formation rate and Vickers hardness Hv were as shown in Table 1.

【table】

[Table] Samples marked with * are outside the scope of the present invention.
As is clear from Table 1, by irradiating with laser light, the film formation speed and hardness are remarkable compared to sample number 9 (no laser light was irradiated and all other manufacturing conditions were kept the same). It can be seen that this has improved. Example 2 A semiconductor laser with the wavelength shown in Table 2 was set to an output power of 350 mW/cm ² and used as a laser projection source.
A BN film was formed under the same manufacturing conditions as in Example 1 except for the following. When the thus obtained BN film was analyzed by X-ray diffraction, CBN (111) was found for sample numbers 11 to 14.
A peak that could be identified as WBN (002) was confirmed, and its existence was confirmed. Furthermore, the Pickkers hardness Hv of these films is as shown in Table 2.

[Table] From Table 2, all samples show remarkable high hardness characteristics, and sample numbers 12 and 13 have remarkable high hardness.
It can be seen that it is a BN film. As described above, the method for producing a high-hardness BN film of the present invention utilizes electron cyclotron resonance excited plasma and further uses an appropriate energy supply method using laser light to produce a high-quality BN film composed of CBN or WBN. could be formed on the substrate at high speed. It should be noted that the present invention is not limited to the above-mentioned method for producing a BN film using electron cyclotron resonance excited plasma, and may be applied to other BN films such as ionization synthesis method, ion plating, sputtering, etc., unless the gist of the present invention is departed from. It is obvious to those skilled in the art that the present invention can also be applied to membrane manufacturing methods.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an electron cyclotron resonance discharge device for forming cubic boron nitride (CBN) and hexagonal close-packed boron nitride (WBN).
The figure shows the infrared absorption spectra of CBN and WBN, and Figure 3 shows the energy potential of the bonding reaction between boron (B) and nitrogen (N). DESCRIPTION OF SYMBOLS 1... Reaction chamber, 2... Electromagnetic coil, 3... Waveguide, 4... First introduction tube, 5... Precipitation chamber, 7... Substrate, 8
...Second introduction pipe, 9...Laser projection source.

Claims (1)

[Claims] 1. A boron nitride generating gas is introduced into a reaction chamber in which a substrate is installed, and plasma is generated inside the reaction chamber to deposit boron nitride on the surface of the substrate by chemical vapor deposition. A method for producing a high-hardness boron nitride film, the method comprising: projecting a laser beam into the plasma inside the reaction chamber to promote bonding between boron atoms and nitrogen atoms. 2. The method for producing a high hardness boron nitride film according to claim 1, wherein the laser beam is within a wavelength range of 7.5 to 12 μm. 3. The method for producing a high hardness boron nitride film according to claim 1, wherein the plasma is generated by electron cyclotron resonance discharge using microwaves.