JP7146946B2 - Process for preparing 3C-SiC films - Google Patents

Description

The present invention relates to SiC-CVD films prepared by hybrid laser CVD, specifically fine-grained 3C-SiC thick films, and processes for preparing same.

Silicon carbide (SiC) is a wide bandgap compound semiconductor material that is highly suitable for use in high power and high frequency electronics due to its high thermal conductivity, breakdown field strength, and saturation velocity. Of these, 3C-SiC has many outstanding features, such as high temperature stability, thermal conductivity, and mechanical strength, as well as excellent chemical attack, thermal shock, and oxidation resistance, making it suitable for use at high temperatures. attractive to

Recently, 3C-SiC thick films have been prepared by hot wall CVD (HCVD), plasma CVD (PECVD), and laser CVD (LCVD). Among these CVD processes, LCVD is the most efficient way to prepare 3C-SiC thick films at low T _dep and with high R _dep . For example, Non-Patent Document 1 discloses 3C-SiC films with mm-scale thickness prepared by continuous diode laser CVD with R _dep of several thousand micrometers per hour at 1673K. Since the thickness of 3C-SiC films was in the millimeter range, the average grain size of 3C-SiC was also increased to tens or hundreds of micrometers.

However, fine microstructured SiC has many mechanical, electrical, and optical properties superior to their coarse grain bulk counterparts. For example, Non-Patent Document 2 discloses fine-grained SiC obtained by propylene pulsing, and the hardness of SiC films ranges from 37 to 43 GPa, which is higher than that of coarse columnar-grained SiC layers. was also about 10% higher. On the other hand, as reported by Barmina et al. [3], SiC with micron- or nanometer-sized structures can improve the performance of light-emitting diodes (LEDs).

Compared with other laser CVD processes such as diode laser (infrared laser) or _CO2 laser CVD, ultraviolet laser CVD has the advantage of making SiC or other ceramic thin films at low temperatures, and the wavelength of the ultraviolet laser beam ( λ) was generally in the range of 100 to 300 nm. Unlike diode laser or _CO2 laser CVD, which are pyrolytic processes, UV laser CVD is a photolytic process. Primarily, the ultraviolet laser beam is absorbed by precursors such as disilane and titanium tetrachloride, which photolyze the molecules, thereby initiating the reaction. Another important application of UV lasers is the surface nanotexturing of SiC. When SiC is irradiated with an ultraviolet laser, a melt layer is obtained by laser pulse explosion, and then the melt solidifies on the SiC surface in the form of spherical or hemispherical nanostructures.

However, in the art, preparation of fine-grained 3C-SiC thick films by laser CVD, which is easier to implement, has a higher deposition rate, and results in 3C-SiC films with higher microhardness there is no process to

H. Cheng, R.; Tu, S.; Zhang, M.; X. Han, T.; Goto, and L. M. Zhang, “Preparation of highly oriented beta SiC bulks by halide laser chemical vapor deposition,” Journal of the European Ceramic Society, Journal of the European Ceramic Society), Vol. 37 [2] p. 509-515 (2017). R. Z. Liu, M.; L. Liu, Z.; L. Wang, Y.; L. Shao, J.; X. Chang, and B.P. Liu, "Preparation of Fine Grained SiC Layer by Fluidized Bed Chemical Vapor Deposition with Pulsed Propylene," Journal of the American Journal of the American Ceramic Society, Vol. 99 [6] p. 1870-1873 (2016). E. V. Barmina, A.; A. Serkov, and G.J. A. Shafeev, "Nanostructuring of single-crystal silicon carbide by picosecond UV laser radiation," Quantum Electronics, Vol. 43 [12 ] p. 1091-1093 (2013).

It is an object of the present invention to solve the above-described problems of the prior art and to produce SiC-CVD films, specifically SiC-CVD films, by a hybrid laser CVD system combining infrared lasers (diode lasers) and ultraviolet lasers. To provide a process for preparing fine grain 3C—SiC thick films.

It is another object of the present invention to provide SiC-CVD films, specifically thick and fine-grained 3C-SiC films, prepared by the above process.

To achieve the above objectives, in one aspect, a process is provided for preparing SiC-CVD films by combined infrared and ultraviolet laser beam CVD:
providing a substrate within a chamber of a laser CVD apparatus;
preheating the substrate and then irradiating the substrate with an infrared laser beam and an ultraviolet laser beam;
introducing a silicon precursor and a carbon precursor, optionally a carrier gas, into the chamber to deposit the SiC-CVD film on the substrate;
including
The deposition temperature is maintained at 1523-1623K in the chamber.

In a preferred embodiment, said resulting SiC-CVD film is a 3C-SiC film; preferably said SiC-CVD film, preferably 3C-SiC film, has an average grain size of 0.5 to 5 μm.

In one embodiment, the laser CVD apparatus is a cold wall laser CVD apparatus.

In one embodiment, the ultraviolet laser beam is applied in pulsed mode. Preferably, the UV laser beam is emitted at 50 mJ/cm ² and at a repetition rate of 10 Hz. Preferably it has a pulse width of 15 ps. Preferably, the ultraviolet laser beam has a wavelength (λ) of 266 nm.

In one embodiment, the infrared laser beam is applied in continuous mode. Preferably, the infrared laser beam is emitted with a power (P _L ) of 200 to 500 W. An infrared laser beam can provide a uniform temperature distribution over the substrate surface. Preferably, the infrared laser beam has a wavelength (λ) of 1060 nm.

In one embodiment, said substrate is preferably a graphite disc.

In one embodiment, the substrate is preferably preheated on a hot stage at T _pre =753K.

In one embodiment, preferably SiCl ₄ and CH ₄ are used as said silicon and carbon precursors respectively and H ₂ is used as said carrier gas. Preferably, the silicon and carbon precursors and carrier gas are each introduced at a flow rate of 200 to 1400 sccm.

In one embodiment, preferably the total pressure (P _tot ) during the process is 4 kPa and the deposition time is 30 min.

In some embodiments, the deposition rate (R _dep ) during the process can be up to 1230 μm/h, preferably in the range of 500 to 1230 μm/h.

In another aspect, SiC-CVD films, preferably fine grain 3C-SiC thick films, prepared by the above process are provided.

In one embodiment, said SiC-CVD film, preferably said 3C-SiC film, has an average grain size of 0.5 to 5 μm.

In one embodiment, the SiC-CVD film, preferably the 3C-SiC film, has a grainy surface and a columnar microstructure, as can be seen from its SEM image. In another embodiment, the SiC-CVD film, preferably the 3C-SiC film, has randomly distributed crystallographic orientations.

In one embodiment, said SiC-CVD film, preferably said 3C-SiC film, has a Vickers microhardness ( _Hv ) up to 35 GPa, preferably from 31 to 35 GPa at 1623 K and 300 g load. .

In the above process, the introduction of an ultraviolet laser can improve the nucleation rate of deposition. Therefore, a SiC-CVD film, preferably a 3C-SiC film, with finer grains and higher microhardness can be obtained by the above process with combined infrared and ultraviolet laser beams, which process Easier to implement and higher deposition rate.

The accompanying drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. These are included to provide a further understanding of the invention and are incorporated as part of this specification.

FIG. 1 is a schematic diagram of a hybrid laser CVD apparatus used to carry out a process according to one embodiment of the invention. FIG. 2 is a graph illustrating the XRD patterns of the 3C—SiC films obtained in Examples 1-2 and Comparative Examples 1-2. FIG. 3 is a graph illustrating Raman patterns of 3C—SiC films obtained in Examples 1-2 and Comparative Examples 1-2. FIG. 4 is a graph illustrating surface and fracture SEM images of 3C—SiC films obtained in Examples 1-2 and Comparative Examples 1-2. FIG. 5 is a graph illustrating the distribution and average grain size of 3C—SiC films obtained in Examples 1-2 and Comparative Examples 1-2. FIG. 6 is a graph illustrating the effect of loading on the Vickers microhardness (H _v ) of the 3C—SiC films obtained in Examples 1-2 and Comparative Examples 1-2. FIG. 7 is a graph illustrating the deposition rate (R _dep ) of the 3C—SiC films obtained in Examples 1-2 and Comparative Examples 1-2.

The advantages and features of the present application may be more readily understood with reference to the following detailed description of examples and accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the examples presented herein. Rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the concepts of this disclosure to those skilled in the art, which disclosure is defined by the following claims.

In this application, the term "diode laser" is synonymous with the term "infrared laser" and the two terms may be used interchangeably in the following text.

As described above, in one aspect, the present invention provides a method for preparing SiC-CVD films, preferably fine-grained 3C-SiC thick films, by CVD with combined infrared and ultraviolet laser beams. Provide process:
providing a substrate in a chamber of a laser CVD apparatus, preferably a cold wall laser CVD apparatus;
preheating the substrate and then irradiating the substrate with an infrared laser beam and an ultraviolet laser beam;
introducing a silicon precursor and a carbon precursor, optionally a carrier gas, into the chamber to deposit a SiC-CVD film, preferably a fine-grained 3C-SiC thick film, on a substrate;
including
The deposition temperature is maintained at 1523-1623K in the chamber.

FIG. 1 shows a cold wall laser CVD apparatus as a hybrid laser CVD apparatus used to carry out a process according to one embodiment of the present invention. As can be seen from FIG. 1, the apparatus 100 includes a housing that defines a chamber 1 for film deposition. An infrared laser 2 and an ultraviolet laser 3 are connected to the apparatus 100 such that an infrared laser beam and an ultraviolet laser beam can be introduced into the chamber 1 through the quartz windows 4, 4', respectively. Also, the infrared laser beam is expanded to 20 mm in diameter by a lens (not shown) to irradiate the entire substrate. A stage 6 is provided at the bottom of the chamber for supporting the substrate 5 . Preferably stage 6 is a heating stage so that the substrate 5 thereon can be preheated in the process. Nozzles 7 are provided immediately above substrate 5 for introducing silicon and carbon precursors and carrier gases. Preferably, nozzle 7 is spaced from the substrate by a distance of 30 mm. The tube is connected on the one hand to a nozzle 7 for introducing gases and on the other hand is fluidly connected via valves 12, 12′, 12″ to sources of silicon and carbon precursors and carrier gas respectively. For example, when SiCl ₄ is used as the silicon precursor, CH ₄ as the carbon precursor, and H ₂ as the carrier gas, the tubes are connected via valve 12 to SiCl ₄ precursor tank 11 and valve 12 ′. to the _CH4 source via and to the H2 source via valve ₁₂ ''. Optionally, SiCl ₄ precursor tank 11 can be further connected to a H ₂ source for delivering SiCl ₄ gas. As shown in _FIG . 1, the pipe for introducing the H2 gas into the tank 11 can be below the level of the _SiCl4 liquid so that the _SiCl4 gas can be carried out of the liquid by bubbling at elevated temperatures. . Additionally, the gas flow can be controlled by the MFC as shown in FIG. A pyrometer 9 can be provided on the housing of the device 100 through another quartz window 8 so that the temperature within the chamber can be monitored in the process. A vacuum pump 10 is provided at the bottom of the device 100 .

Unlike the diode laser CVD apparatus, the hybrid laser CVD apparatus according to the present invention adds a quartz window for passing the ultraviolet laser beam. Ultraviolet lasers can have typical wavelengths of, for example, 100 to 300 nm. For infrared lasers, it can have wavelengths that are frequently used in the field.

In the process, the deposition rate (R _dep ) can be up to 1230 μm/h. A method for measuring the deposition rate (R _dep ) is described next.

Other (preferred) features relating to the process according to the invention are as described above.

In another aspect, the present invention provides SiC-CVD films, preferably fine-grained 3C-SiC thick films, prepared by the above process. SiC-CVD films, preferably 3C-SiC films, may have an average grain size of 0.5 to 5 μm. As can be seen from its SEM images, SiC-CVD films, preferably 3C-SiC films, can have grainy surfaces and columnar microstructures, and randomly distributed crystallographic orientations. In addition, SiC-CVD films, preferably 3C-SiC films, can have Vickers microhardness (H _v ) up to 35 GPa at 1623 K and 300 g load loading. Methods for measuring average grain size and Vickers microhardness ( _Hv ) are described next.

Hereinafter, the invention will be described by way of example, but the following examples are provided merely to enable a clearer understanding of the invention rather than to limit its scope.

<Example 1>
Fabrication of 3C-SiC film
Fine-grained 3C—SiC films were prepared using the cold-wall hybrid laser CVD apparatus shown in FIG. A quartz window 4' was added to allow passage of an ultraviolet laser beam (β-BaB ₂ O ₄ , wavelength = 266 nm). A UV laser was irradiated at 50 mJ/cm ² and at a repetition rate of 10 Hz. The pulse width was 15 ps. A graphite disc (IGS-743, Φ15 mm×1 mm, Sankyo Carbon Co., Ltd., Tokyo, Japan) was used as a substrate and preheated on a hot stage at T _pre =753K. An infrared laser beam (InGaAlAs, wavelength = 1060 nm) was introduced into the chamber through a quartz glass window 4 and expanded to a diameter of 20 mm by a lens to irradiate the entire substrate. The laser was operated in continuous mode with a power output (P _L ) between 200 and 500 W. The deposition temperature (T _dep ) was measured by a thermocouple and pyrometer (2MH-CF4, Optris GmbH, Berlin, Germany) and controlled within ±5K over the entire substrate at 1523K. The infrared laser beam provided a uniform temperature distribution over the substrate surface. _SiCl4 and CH4 _were used as silicon and carbon precursors, respectively. _SiCl4 was vaporized at ₂₉₃ K and carried into the CVD chamber by H2 gas. The SiCl ₄ , CH ₄ and H ₂ flow rates were fixed at 400, 200 and 1400 sccm respectively. The total pressure (P _tot ) and deposition time were 4 kPa and 30 min, respectively. The distance between nozzle and substrate was 30 mm. The gas nozzle temperature was recorded by a thermocouple at 473K. A cold trap filled with liquid nitrogen and a NaOH spray scrubber were applied to treat harmful exhaust gases (eg intermediate Si—C—H—Cl) and HCl.

The measured crystalline phase was investigated by X-ray diffraction (θ-2θ) with Cu-Kα (40 kV and 40 mA) radiation (XRD, Ultima-III, Rigaku, Tokyo, Japan).
A Raman spectrometer (LabRam HR800Ev, Horiba, Ltd., Kyoto, Japan, with a 532 nm He—Ne laser) was used for Raman spectral measurements of the 3C—SiC films.
The microstructure of the specimen was observed by SEM (Quanta-250, FEI, 20 kV, Houston, USA) and the deposition rate (R _dep ) was calculated from the thickness and deposition time.
The microhardness of the 3C—SiC films was measured with a Vickers microhardness tester (430SVD, Wolpert, USA) at loads of 300, 500, and 1000 g. The indentation time was 15 s and the thickness of the 3C—SiC film for the hardness test was thick enough to eliminate the substrate effect.
Average grain size was determined from SEM images by counting straight lengths with at least 100 grains.

The XRD pattern and Raman scattering spectrum of the resulting 3C-SiC film are shown in FIGS. 2 and 3, respectively (indicated by (c)). SEM images are shown in FIGS. 4(e) and (f). The average grain size and Vickers microhardness are shown in FIGS. 5 and 6, respectively (indicated by (c)). R _dep is shown in FIG.

<Example 2>
A 3C-SiC film was fabricated and measured in the same manner as in Example 1, except that the deposition temperature (T _dep ) was 1623 K and controlled within ±5 K across the substrate.

The XRD pattern and Raman scattering spectrum of the resulting 3C-SiC film are shown in Figures 2 and 3, respectively (indicated by (d)). SEM images are shown in FIGS. 4(g) and (h). The average grain size and Vickers microhardness are shown in FIGS. 5 and 6, respectively (indicated by (d)). R _dep is shown in FIG.

<Comparative Example 1>
A 3C-SiC film was fabricated and measured in the same manner as in Example 1, except that no ultraviolet laser beam was introduced into the process; that is, the 3C-SiC film was fabricated by a diode (infrared) laser CVD process did.

The XRD pattern and Raman scattering spectrum of the resulting 3C—SiC film are shown in FIGS. 2 and 3, respectively (indicated by (a)). SEM images are shown in FIGS. 4(a) and (b). The average grain size and Vickers microhardness are shown in FIGS. 5 and 6, respectively (indicated by (a)). R _dep is shown in FIG.

<Comparative Example 2>
A 3C-SiC film was fabricated and measured in the same manner as in Example 2, except that no ultraviolet laser beam was introduced into the process; did.

The XRD pattern and Raman scattering spectrum of the resulting 3C—SiC film are shown in FIGS. 2 and 3, respectively (indicated by (b)). SEM images are shown in FIGS. 4(c) and (d). The average grain size and Vickers microhardness are shown in FIGS. 5 and 6, respectively (indicated by (b)). R _dep is shown in FIG.

<Evaluation>
XRD pattern
FIG. 2 shows 3C-SiC films deposited by diode laser CVD (Comparative Examples 1-2, (a) and (b)) and hybrid laser CVD (Examples 1-2, (c) and (d)). shows the XRD pattern of The five prominent diffraction peaks at 2θ=35.7°, 41.3°, 60°, 71.8°, and 75.5° are (111), (200), (220) of 3C-SiC, respectively. , (311), and (222) planes. As shown in curves (a) and (b) in Fig. 2, in the 3C-SiC films prepared by diode laser CVD, the (220) peak is stronger than the others, indicating the preferential orientation of the (220) plane. showed that. However, in the 3C—SiC films deposited by hybrid laser CVD, several major peaks were observed [curves (c) and (d) in FIG. 2]. It implied that the grains of the crystal were randomly distributed in crystallographic orientation. The orientation of the 3C-SiC films was evaluated by the Lotgering factor (F _hkl ). Table 1 shows the F ₁₁₀ and F ₁₁₁ of 3C—SiC films prepared by diode laser CVD and hybrid laser CVD. F _hkl was calculated from equation (1):
F _hkl = (P _hkl − P ₀ )/(1−P ₀ ) Equation (1)
where P _hkl and P ₀ are the ratios of the peak intensity of the (hkl) plane and the sum of all peaks for film (P _hkl ) and powder (P ₀ ), respectively. The F _hkl factor has values from negative (orientation along the other axis) to 0 (random) to 1 (perfect orientation). The orientation of 3C-SiC films changed significantly with hybrid laser CVD. The 3C—SiC films prepared by diode laser CVD exhibited F ₁₁₀ values higher than 0.6 and had negative F ₁₁₁ values, indicating <110> orientation. On the other hand, the F ₁₁₀ and F ₁₁₁ values of the 3C—SiC films were close to 0, indicating random orientation. A small shoulder was observed between 2θ and 33.8° in specimens prepared by hybrid laser CVD, which could be attributed to planar defects. Planar defects and preferential orientation disturbances could be induced by UV laser irradiation in hybrid laser CVD.

Raman of 3C-SiC Films Grown by Raman Spectral Diode Laser CVD (Comparative Examples 1-2, (a) and (b)) and Hybrid Laser CVD (Examples 1-2, (c) and (d)) A scattering spectrum is shown in FIG. Curves (a) and (b) show Raman spectra of 3C—SiC films prepared by diode laser CVD. It consists of two mainly sharp peaks at 796 and 972 cm ⁻¹ , which are assigned to the transverse optical (TO) and longitudinal optical (LO) modes of 3C—SiC, respectively. Two peaks around 1520 and 1710 cm ⁻¹ were attributed to second order optical phonon modes. In addition, there were no faint carbon phase peaks [D (~1330 cm ^-1 ) and G (~1580 cm ^-1 )] in the spectrum. Curves (c) and (d) show Raman spectra of 3C-SiC films prepared by hybrid laser CVD. It also mainly consisted of two peaks at 796 and 972 cm ⁻¹ , which were unchanged in hybrid laser CVD. In addition to these peaks, two broad peaks between 150 and 600 cm ⁻¹ were detected in specimens prepared by hybrid CVD. This can be assigned either to the silicon carbide acoustic phonon mode, which has been reported specifically for smaller SiC crystallites, or to the TO phonon mode of amorphous silicon. a-Si has also been reported to be made by UV laser irradiation of SiC. The shoulders observed on the low cm ⁻¹ side of the TO and LO peaks suggested a number of defects. This result was consistent with the XRD pattern. XRD and Raman peak full width at half maximum (FWHM) are presented in Table 2. The FWHM of the TO and LO Raman peaks of 3C—SiC prepared by hybrid laser CVD were much higher than those of specimens deposited by diode laser CVD. The broadening was believed to be due to the small size of the SiC grains. The FWHM of the XRD peaks showed similar results, which also supported that the 3C-SiC prepared by hybrid laser CVD had a much smaller grain size.

SEM images FIG. 4 show 3C-SiC prepared by diode laser CVD (Comparative Examples 1-2, (a) to (d)) as well as hybrid laser CVD (Examples 1-2, (e) to (h)). The surface and fracture microstructure of the membrane are shown. The 3C—SiC films deposited by diode laser CVD exhibited roof-like faceted surfaces [FIGS. 4(a) and (c)] and columnar cross-sections [FIGS. 4(b) and (d)]. It was found that the columnar crystal grains exhibited a well-aligned columnar microstructure, although some deviations from the growth direction were detected. These typical surface and fracture microstructures of <110> oriented 3C—SiC films are similar to previous studies in the field. However, the 3C-SiC films prepared by hybrid laser CVD exhibited a different microstructure. A fine granular surface structure [FIGS. 4(e) and (g)] was observed. The pillars [FIGS. 4(f) and (h)] did not extend through the entire thickness of the 3C—SiC film, but were limited in length and width. This suggests continuous nucleation of new species, which may be due to the enhanced nucleation rate by the UV laser in hybrid laser CVD.

Grain size Figure 5 shows 3C- 3C- Fig. 3 presents the grain size distribution of SiC films; Figures 5(a) and (b) show the grain size distribution of 3C-SiC prepared by diode laser CVD. At T _dep =1523 and 1623 K, the surface structure of the 3C—SiC films has grain sizes in the range of 4-27 and 10-100 μm, respectively. The grain size distribution of 3C-SiC films prepared by hybrid CVD is shown in FIGS. 5(c) and (d). The grain size distributions ranged from 0.5 to 3.5 and 1.5 to 5.5 μm, respectively. Table 3 shows the average grain size of 3C-SiC prepared by diode laser CVD and hybrid laser CVD. The average grain size was greatly reduced in the 3C-SiC films prepared by hybrid laser CVD. The average grain size of 3C—SiC prepared by diode laser CVD was 52.8 and 13.2 μm, respectively. However, for 3C-SiC prepared by hybrid CVD, the average grain size decreased to 1.2 and 2.6 μm, respectively. Normally, when an ultraviolet laser beam hits a target, nanoparticles are generated directly from the irradiated sample, and nanoparticle formation is initiated by pico- or femtosecond laser-induced Coulomb explosions, which is one of the factors in SiC films. leading to a uniformly distributed microstructure.

Vickers microhardness Figure 6 shows the 3C- Effect of loading on the Vickers _{microhardness} (HV) of SiC films. The _HV of the 3C—SiC film decreased with increasing indenter loading. In principle, hardness should be independent of load application, since the shape of the indentation is independent of its size. However, in practice there is a load dependence of the indentation, especially at small loads. The total indentation is that obtained by plastic deformation minus the amount of elastic recovery due to unloading. At lower loads, the amount of elastic recovery is a greater percentage of the total indentation than at higher loads. Therefore, usually the measured hardness values at lower loads are higher compared to those at higher loads. For ceramic materials, it is well known in the prior art that hardness decreases with increasing load. The _HV of 3C-SiC films prepared by hybrid laser CVD was much higher than diode laser CVD. At 1623 K and a load of 300 _g , HV increased from 31 to 35 GPa for hybrid laser CVD. The enhanced _HV could be caused by the much smaller grain size of hybrid laser CVD 3C-SiC films.

R _dep
FIG. 7 shows the R _dep of 3C—SiC films prepared by diode laser CVD (Comparative Examples 1-2, indicated by open circles) and hybrid laser CVD (Examples 1-2, indicated by solid circles). showing. At 1523 and 1623 K, R _dep was 440 to 935 μm/h for diode laser CVD. Hybrid laser CVD increased R _dep to 500 and 1230 μm/h. Unlike the diode laser CVD process, the photothermal deposition process could be photolytically enhanced by the ultraviolet laser beam in the hybrid laser CVD process. The decomposition rate of the precursor was improved when the 3C—SiC films were deposited by hybrid laser CVD. Then the growing surface will receive more radicals, leading to an improvement in R _dep .

As can be seen above, fine-grained 3C—SiC thick films were fabricated by hybrid laser CVD combining infrared and ultraviolet laser beams. The introduction of UV laser had a great impact on the preferred orientation, microstructure, H _v and R _dep of 3C-SiC films. A 3C-SiC film with coarse grains and <110> orientation was obtained by diode laser CVD, and the grain size was in the range of 5 to 100 μm. Fine-grained and randomly oriented 3C—SiC films ranging from The 3C—SiC films prepared by diode laser CVD exhibited roof-like faced surfaces and well-aligned columnar microstructures, whereas the hybrid laser CVD process resulted in grainy surfaces and columnar microstructures. In hybrid laser CVD, columnar grains were limited in length and width due to enhanced nucleation by the UV laser. Due to the much smaller grain size, hybrid laser CVD also improved the HV and R _dep of the 3C—SiC films, eg at 1623 K and a load of 300 _g . The HV of the 3C-SiC films increased from 31 to 35 _{GPa and the R dep increased} from 935 to 1230 μm/h, respectively.

Although specific embodiments of the invention have been described above, various adaptations and modifications will be readily apparent to those skilled in the art without departing from the scope of the invention.

1 chamber 2 infrared laser 3 ultraviolet laser 4 quartz window 4′ quartz window 5 substrate 6 stage 7 nozzle 8 quartz window 9 pyrometer 10 vacuum pump 11 SiCl ₄ precursor tank 12 valve 12′ valve 12″ valve 100 apparatus

Claims (5)

A process for preparing a SiC-CVD film by CVD with combined infrared and ultraviolet laser beams, comprising:
providing a substrate in a chamber of a cold-wall laser CVD apparatus;
preheating the substrate and then irradiating the substrate with an infrared laser beam and an ultraviolet laser beam;
introducing a silicon precursor and a carbon precursor, optionally a carrier gas, into the chamber,
forming the SiC-CVD film on the substrate;
including
a deposition temperature is maintained at 1523 to 1623 K by the infrared laser beam in the chamber;
process. The process of claim 1, wherein said SiC-CVD film is a 3C-SiC film. The process according to claim 1 or 2, wherein said SiC-CVD film has an average grain size of 0.5 to 5 µm. A process according to any preceding claim, wherein the silicon precursor is SiCl ₄ , the carbon precursor is CH ₄ and the carrier gas is H ₂ . The process of any one of claims 1-4, wherein the substrate is a graphite disc.

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