JPH054807A - Production of boron nitride film - Google Patents

Abstract

PURPOSE:To provide a novel method capable of producing and depositing a highly pure cubic boron nitride film on the surface of a substrate at a high speed. CONSTITUTION:A method for producing a cubic boron nitride film comprising irradiating a boron atom-containing target with an excimer laser in a nitrogen atom-containing gas atmosphere to form the film on a substrate arranged opposedly to the target, characterized by irradiating the particles produced by the irradiation of the laser with a laser having a wavelength of 150 to 360nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cubic boron nitride film used for cemented carbide tools, insulating films, heat conductive films, semiconductors and the like.

[0002]

2. Description of the Related Art As a method for synthesizing cubic boron nitride (hereinafter also referred to as c-BN) from a vapor phase, there are, for example, the following three known techniques. As described in JP-A-60-181626, boron is vapor-deposited on a substrate from an evaporation source containing boron, and at the same time, the substrate is irradiated with the contained ion species from an ion generation source that generates ion species containing at least nitrogen. Then, a method for producing a cubic boron nitride film, in which boron nitride is produced on the substrate. Method for producing cubic boron nitride on a substrate by chemically transporting boron by H ₂ + N ₂ plasma [Reference 1: Komatsu et al., Journal
Of Materials Science Letters, Journalo
f Materials Science Letters, 4 (1985) pp5
1-54]. HCD (Hollow cathode Discharge
Hollow cathode cathode discharge) While vaporizing boron with a gun, N ₂ is ionized from the hollow electrode to irradiate the substrate, a high frequency is applied to the substrate to have a self-bias effect, and boron nitride is deposited on the substrate. Method of generation [Reference 2:
Inagawa and others, Proceedings of 9th Symposium on Ion Assis
ted Technology, '85, Tokyo, pp299-302
(1985)].

[0003]

In any of the above methods, it is hard to say that cubic boron nitride having excellent crystallinity is obtained at present. That is, a single-phase film made of c-BN alone has not been obtained by the conventional manufacturing method, and is a film containing hexagonal boron nitride (hereinafter also referred to as h-BN) and / or amorphous boron nitride. It is an object of the present invention to solve the drawbacks of the conventional method and to provide a novel method for producing a boron nitride film capable of producing and depositing a high-purity cubic boron nitride thin film on the surface of a substrate at high speed.

[0004]

As a means for solving the above-mentioned problems, in the present invention, a target containing boron atoms is irradiated with excimer laser light, and a substrate arranged facing the target in a gas atmosphere containing nitrogen atoms. In the method for synthesizing a cubic boron nitride film, a method for producing a boron nitride film, characterized in that the particles produced by the laser irradiation are irradiated with laser light having a wavelength of 150 nm to 360 nm.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a conceptual diagram showing a specific example of the present invention. A target 3 placed on a target holder 2 and a substrate 5 on a substrate holder 4 facing the target 3 are arranged in the film forming chamber 1. As the target 3, simple substance of boron, hexagonal boron nitride (h-BN), pyrolytic B
(Referred to as p-BN) N, single crystal or polycrystal c-BN, etc. H ₃ BO ₃ is used. The substrate 5 is heated to 300 ° C. to 1300 ° C. by the heater 6. In the film forming chamber 1, a gas containing nitrogen atoms such as N ₂ and NH ₃ , a gas containing hydrogen or fluorine such as H ₂ , F ₂ and CF _4, and an inert gas such as He and Ar are supplied by the gas supply device 7. Introduced from. Film formation pressure is 10 ^-5 Torr to 10 Tor
Let r. The laser light emitted from the excimer laser device 8 is first branched using the beam splitter 9, and one laser light 13 is condensed by the condenser lens 10 and passed through the entrance window 11 to the surface of the target 3 in the film forming chamber 1. To irradiate. The laser power density on the target surface is in the range of 0.5 Jcm ^{-2 to} 100 Jcm ^-2 . The other laser light 14 is irradiated between the target 3 and the substrate 5 by using the laser light reflecting mirror 12 and the condenser lens 10, and the excited species 15 (generally called plume; generated from the target by the laser light 13). The plume) will be irradiated with laser light. The laser power density at this time is 0.1 to 20 Jcm.
The range is ^-2 . The laser light 14 for irradiating the plume may use a laser 16 having a wavelength different from that of the laser 13 for irradiating the surface of the target 3. In this case, the wavelength of the laser light needs to be 150 nm to 360 nm. Further, the laser for irradiating the plume is not limited to the pulse laser and may be a continuous light source. FIG. 2 shows a specific example in which the plume is irradiated with laser light using a laser different from the laser used for irradiating the target. By such a method, the c-BN film can be manufactured.

[0006]

[Function] The excimer laser has an oscillation wavelength in the ultraviolet region, and F ₂ (15
7 nm), ArF (193 nm), KrCl (222n)
m), KrF (248 nm), XeCl (308n
m) and XeF (351 nm). The reason for using these excimer lasers in the present invention is that, first of all, one photon has a large energy. For example, in the case of ArF excimer laser, the oscillation wavelength is 193 nm, which corresponds to energy of 6.42 eV. On the other hand, a CO ₂ laser which is usually used as an industrial laser other than the excimer laser has an oscillation wavelength of 10.6 μm, which is 0.1 at most.
The energy is only 2 eV. Secondly, since the laser light can be condensed by using an optical system such as a lens, the energy density can be further increased. By irradiating such a high-energy laser, the target is decomposed and a plume accompanied by light emission is generated, whereby boron nitride can be synthesized. However, the boron nitride film thus obtained becomes c-BN containing h-BN and amorphous boron nitride and having poor crystallinity. According to the findings of the present inventors, the plume is further excited by further irradiating the plume generated from the target by irradiating the laser with the laser beam, which leads to the production of c-BN having good crystallinity. It turned out to be important.

[0007] In the present invention, the laser power density on the target surface, depending like the target and the substrate distance, 0.5Jcm ^-2 ~100Jcm ^-2 are preferred. If the power is lower than the above range, the particles decomposed from the target will be insufficiently excited and the film growth rate will be low. On the other hand, if it is too high, many clusters will occur,
This is because a good cubic boron nitride film cannot be formed.

On the other hand, the power of the laser light applied to the plume
ー Density is 0.1cm^-2~ 20 Jcm ^-2Is preferred. 0.
1 cm^-2If it is less than the following, the effect of irradiating the substrate with laser light is extremely high.
Become smaller. 20 Jcm^-2If stronger than
Is the direction in which the plume flies due to the irradiation pressure of the laser.
Not only is it bent, but the plume itself is active
Too much, and rather the amount of amorphous components increased
End up.

The wavelength of the laser beam for irradiating the plume is preferably 150 nm to 360 nm. If the thickness is 150 nm or less, the laser beam is absorbed by the nitrogen atom-containing gas in the film forming chamber, and the plume is not actually irradiated with the laser beam, so that the effect of the present invention is not obtained. 360n
At wavelengths longer than m, the photon energy of the emitted laser light becomes small (3.53e at 360 nm).
V). There are clusters in the plume that are not completely decomposed into atoms, but in order to decompose these clusters, it is necessary to irradiate photons with sufficient energy to break the bonds between the atoms that make up the clusters. In the case of BN, it has a binding energy of about 7 eV, so 3.53 eV
In the case of a laser having a wavelength of 360 nm having the energy of, two-photon absorption may occur. However, lasers with wavelengths longer than 360 nm must simultaneously absorb more than three photons, and the probability of simultaneous absorption of more than three photons is low, so clusters in the plume have lasers with wavelengths longer than 360 nm. The irradiation hardly contributes to the excitation of the plume, and the effect of the present invention is low. Further, in the case of BN, absorption is extremely small for wavelengths longer than 360 nm, and for this reason also the effect of the present invention becomes low.

[0010] Incidentally, the irradiating laser to the plume only to be irradiated in the plume but, in particular 10 ⁵ cm · se
It is preferable to irradiate plume constituent particles having a velocity lower than about c ⁻¹ . Therefore, if the distance between the position of the laser beam radiated to the plume on the plume and the target is d (see FIG. 2), when d = 0 mm, the laser radiated to the target and the laser radiated to the plume are almost the same. Irradiation is preferably performed at the same time (according to the studies made by the present inventors, it is most preferable to irradiate the plume with a laser about 200 nsec. Late at d = 0 mm), but 10 μsec. At d = 10 mm. It is preferable to irradiate the plume with a laser about as slowly as possible.

In the present invention, the film forming pressure is appropriately selected depending on other manufacturing conditions, particularly the distance between the substrate and the target, but 10 ^-5 Torr to 10 Torr is preferable. At a pressure higher than this, the plume is unlikely to reach the substrate, and the particles that make up the plume fall from the excited state to the ground state due to many collisions with gas molecules, making it difficult to synthesize c-BN. At a pressure lower than 10 ^-5 Torr, nitrogen in the target is easily released, and the B: N ratio of the formed film also deviates from the stoichiometric ratio.

According to the studies conducted by the present inventors, the irradiation angle of the laser in the present invention to the target is preferably 30 ° ± 30 ° with respect to the target surface. The reason is not clear, but the crystallinity is extremely low except for this irradiation angle.
-Only BN can be synthesized.

In the present invention, the distance between the target and the substrate is also important as a film forming parameter. It is usually kept between 10 mm and 150 mm, depending on other parameters. The reason is that if the thickness is less than 10 mm, the film formation rate is too high and the amount of B in the film increases, and if it exceeds 150 mm, it becomes difficult for excited species accompanied by light emission to reach the substrate, and the film formation rate is extremely low. Because it is not practical. In the present invention, the laser power, the film forming pressure, and the distance between the target and the substrate are mutually related to control the gas phase reaction, and a desired value can be selected.

The substrate temperature is important as a parameter for crystal formation. In the present invention, formation of a film containing a c-BN crystal was observed even at room temperature. However, in order to further improve the crystallinity, it is preferable to heat the substrate at 300 ° C to 1300 ° C. If the temperature is lower than 300 ° C., the migration of the reaching particles on the film growth surface is not sufficiently performed, and the amorphous component increases. If it exceeds 1300 ° C., the hexagonal crystal component increases, and the heat resistance of the substrate often becomes a problem, which is not practical. Although not shown in the example, a high frequency or direct current voltage is appropriately applied to the substrate.

The substrate used in the present invention can be appropriately selected by the parties according to its purpose, and is not particularly limited, but Si, diamond, Mo, WC, iron-based materials, Si ₃ N _4, etc. A cubic boron nitride film can be synthesized using the ceramics or the like as a substrate.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples, but the invention is not limited thereto. 1 or 2
A cubic boron nitride film was prepared by using the above apparatus using Si as a substrate under the following manufacturing conditions. Table 1 shows the film forming conditions, the results of X-ray diffraction [half-width of 111 diffraction peak: angle of 2θ], and c-BN / h-BN obtained from infrared absorption spectrum.
The results of peak ratio and film composition analysis (B: N ratio) are shown. Manufacturing conditions Excimer laser: Fe (157 nm), ArF (19
3 nm), KrF (248 nm) or XeF (351
nm) Target: h-BN, c-BN polycrystal (Tc-B)
_{N), H 3 BO 3,} B _{gas: N 2, NH 3: H} 2,
F ₂ , Ar, etc. Gas pressure: 5 × 10 ⁻³ Torr Substrate: Si target-substrate distance: 30 mm Substrate temperature: 650 ° C.

The plume was not irradiated with the laser beam in the apparatus shown in FIG. 1 or 2, and the other conditions were as in Examples 1, 4 and
Comparative examples 1, 2, and
The results are shown in Table 1. Comparative Example 2
JP-A-60-181262 proposes an IVD method (Ion Vapor Deposition method: an ion source for depositing boron on a substrate from an evaporation source containing boron and generating an ion species containing at least nitrogen). A method for irradiating a substrate with ionic species to form a film of boron nitride on the substrate, the ion acceleration energy of the ionic species being 5 to 100 eV per atom of the ionic species, which is lower than the ionic species. According to the method of performing vapor deposition and irradiation in an atmosphere of activated nitrogen atoms or nitrogen compounds),
A trial production of a boron nitride film under the following conditions was evaluated in the same manner as in Example 1. The results are also shown in Table 1. Manufacturing conditions Evaporation source: B (boron) metal N ₂ ⁺ acceleration energy: 15 eV N ₂ atmosphere pressure: 4 × 10 ⁻⁵ Torr Substrate: Si Substrate temperature: 400 ° C.

[0018]

[Table 1]

[Table 2]

[Table 3]

From the results of Table 1, according to the present invention, there is no h-BN component, the half width of the X-ray diffraction peak is small (1.8 ° → 1.2 ° on average), and the crystallinity is good, and the chemical property is high. It is clearly seen that a high quality c-BN film with a stoichiometric ratio is obtained.

[0020]

As described above, according to the present invention, a target containing boron atoms is irradiated with an excimer laser beam, and a cubic boron nitride film is formed on a substrate arranged facing the target in a gas atmosphere containing nitrogen atoms. In the method of synthesizing
A high-quality cubic boron nitride film can be stably obtained by means of irradiating a laser beam having a wavelength of m to 360 nm.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing one embodiment of a system suitable for performing the method of the present invention.

FIG. 2 is a schematic diagram showing another embodiment of a system suitable for carrying out the method of the present invention.

[Explanation of symbols]

 1: Deposition chamber 2: Target holder 3: Target 4: Substrate holder 5: Substrate 6: Heater 7: Gas supply device 8: Excimer laser 9: Beam splitter 10: Condenser lens 11: Incident window 12: Reflection for laser light Mirror 13: Laser light 14: Laser light 15: Plume 16: Excimer laser for plume irradiation

Claims (1)

Claim: What is claimed is: 1. A target containing boron atoms is irradiated with excimer laser light to synthesize a cubic boron nitride film on a substrate arranged facing the target in a gas atmosphere containing nitrogen atoms. A method for producing a boron nitride film, comprising irradiating particles generated by the laser irradiation with a laser beam having a wavelength of 150 nm to 360 nm.