Silicon carbide thin film and vapor deposition method thereof

Abstract

To provide a vapor deposition technique that overcomes the drawbacks of these and other known deposition techniques by forming high-quality, stoichiometric, as-deposited SiC thin films with minimal defect and hydrogen inclusion, while eliminating the issues associated with current silicon and carbon source precursors.SOLUTION: A vapor deposition method is provided for the growth of as-deposited hydrogen-free silicon carbide (SiC) and SiC films including oxygen (SiC:O) thin films. For producing the SiC thin films, the method includes providing a silahydrocarbon precursor, such as TSCH (1,3,5-trisilacyclohexane), in the vapor phase, with or without a diluent gas, to a reaction zone containing a heated substrate, such that adsorption and decomposition of the precursor occurs to form stoichiometric, hydrogen-free, silicon carbide (SiC) in a 1:1 atom ratio between silicon and carbon on the substrate surface without exposure to any other reactive chemical species or co-reactants. For the SiC:O films, an oxygen source is added to the reaction zone to dope the SiC films with oxygen. In the silahydrocarbon precursors, every carbon atom is bonded to two silicon atoms, with each silicon atom being additionally bonded to two or more hydrogen atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 085,617, filed September 30, 2020, the entire disclosure of which is incorporated herein by reference mutatis mutandis. [Background technology]

[0002] Silicon carbide (SiC) thin films are attracting increasing research interest across multiple application areas. The attractiveness of SiC coatings stems from their highly desirable combination of physical, mechanical, electrical, and optoelectronic properties, making them attractive candidates for applications in the automotive, aerospace, computer chip, solar, light emitting, and medical industries.

[0003] SiC coatings are used as hard protective coatings under harsh thermal, environmental, and chemical conditions due to their high hardness (potentially exceeding 40 GPa), effective oxidation resistance, high-temperature and thermal shock resistance, chemical stability, and attractive mechanical, tribological, and dielectric properties. Ultrathin SiC films are utilized in a wide range of applications, including integrated circuit (IC) technology, particularly in microprocessor units (MPUs), systems-on-chips (SoCs), flash memory, and the vertical stacking of electronic devices, commonly referred to as three-dimensional (3D) integrated systems. For example, SiC is applied as a diffusion barrier in combination with low-k dielectric constant (κ) materials to replace silicon dioxide (SiO2). Similarly, SiC is used as a capping layer and etch stop for copper interconnects.

[0004] Similarly, SiC thin films, due to their wide bandgap (2.3 eV) and elevated electrical breakdown voltage, have been successfully incorporated into active optical and optoelectronic devices, including panel displays, lighting, and light-emitting devices. In this regard, SiC thin films are used as permeation barrier and encapsulation layers in light-emitting devices (LEDs) and organic light-emitting diodes (OLEDs), as well as in the fabrication of various planar optical systems and optical waveguides. Furthermore, SiC coatings have also been proposed for use as passivation layers in flexible electroluminescent devices. The applications of SiC also extend to the green energy sector, primarily in photovoltaic applications. For example, microcrystalline and amorphous SiC coatings are employed as window layers in thin-film solar cells. Similar to the hard coat and computer chip industries, SiC thin films are also applied as passivation layers in silicon solar cells.

[0005] Despite these extensive research and development efforts, significant challenges must be overcome before SiC thin films can be extended to new industrial applications, such as heterogeneous devices. For example, the majority of current SiC vapor deposition methods rely on the high-temperature reaction of silane or halide-type precursors, e.g., SiH4, Si2H6, and SiCl4, with C-containing precursors, e.g., CHCl3, C3H4, C2H2, and CCl4. The inherent challenges associated with the use of these chemicals are well documented and include their flammable nature, numerous environmental, health, and safety issues, high levels of hydrogen incorporation into the resulting SiC films, and the need for post-deposition annealing to achieve the desired SiC film specifications. Two parameters for describing the quality of hydrogenated amorphous silicon carbide thin films are the empirical formula a-Si 1-x C 1+x :H, where x refers to substitutional bonding of hydrogen to silicon atoms that disrupts the 1:1 stoichiometry of Si to C atoms, and :H represents doped H atoms (possibly including interstitial doping) that do not change the Si:C stoichiometry from 1:1. Lowest levels of either type of H defect are highly desirable for quality silicon carbide.

[0006] Prior art efforts to address these challenges include the use of plasma-assisted atomic layer deposition (PA-ALD) of TSCH (1,3,5-trisilacyclohexane) at temperatures below 600°C, preferably between 100 and 200°C (U.S. Pat. No. 8,440,571); the application of ultraviolet light treatment to selectively remove some precursor ligands and deposits to achieve molecular layer deposition (U.S. Pat. No. 8,753,985); and remote plasma processing to create a plasma effluent that produces a flowable layer on the substrate (U.S. Patent Application Publication No. 2013 / 0217239). Unfortunately, all of these methodologies failed to deposit true stoichiometric SiC phases, instead resulting in films consisting of a network of silicon-carbon-hydrogen configurations with varying silicon-to-carbon ratios, fluctuating hydrogen content, and significant defect levels. Not only is hydrogen inclusion of serious concern due to its significant impact on the physical, chemical, electrical, and optoelectronic properties of the films, but the nature of the Si-H and C-H bonds also plays a major role in tuning the resulting film properties.

[0007] Another influencing factor is the Pauling relative electronegativity of the elements Si, C, and H (i.e., Si: 1.90, C: 2.55, H: 2.20). The Si-C bond has a relatively high dipole moment, while the Si-H bond has a relatively low dipole moment. Therefore, even if the atomic percentages of film compositions prepared by known methods are identical, the atomic bonding arrangements of the resulting films may be different, and the dielectric properties of the resulting films may differ. Furthermore, the need for a post-deposition high-temperature anneal to remove H and reduce defect density adds complexity and cost, limiting the use of these known processes to applications that do not require thermally sensitive substrates.

[0008] Another attempt to solve these problems involved the soft template method (STA), in which the final material was defined by the self-assembly of a soluble directing agent (SDA) in a solvent using TSCH, with the SDA acting as a supramolecular template and the solvent acting as the SiC precursor. However, this method had many challenges that made it highly unsuitable for semiconductor, optical, and optoelectronic applications. These challenges include: (i) the pyrolysis of the precursor was carried out at very high temperatures (1000 °C); (ii) the SDA medium required a week to achieve polymerization; (iii) the resulting SiC was a powder exhibiting a porous granular morphology as stacked spherical grains that could not be grown as a thin film; and (iv) the STA method was solvent-based and liquid-phase, making it unsuitable for integration into typical manufacturing processes in the semiconductor, energy, optical, and optoelectronic industries. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 8,440,571 [Patent Document 2] U.S. Patent No. 8,753,985 [Patent Document 3] U.S. Patent Application Publication No. 2013 / 0217239 [Non-patent literature]

[0010] [Non-Patent Document 1] A. Kleinovaet al, "FTIR spectroscopy of silicon carbide thin films prepared by PECVD technology for solar cell application," Proc. SPIE 9563, Reliability of Photovoltaic Cells, Modules, Components, and Systems VIII, 95630U (September 2015) [Non-patent document 2] S. Gallis et al “Photoluminescence at 1540 nm from erbium-doped amorphous silicon carbide films” J. Mater. Res., 19(8), 2389-2893, 2004 Summary of the Invention [Problem to be solved by the invention]

[0011] For these reasons, it would be desirable to provide a deposition technique that overcomes the shortcomings of these and other known deposition techniques by forming high-quality, stoichiometric, as-deposited SiC thin films with minimized defects and hydrogen contamination, while eliminating the problems associated with current silicon and carbon source precursors. It would be further desirable if the vapor deposition method minimized the number and complexity of current processing conditions, thereby maximizing process safety, effectiveness, and productivity. It would also be desirable if such a deposition technique controlled the SiC microstructure by varying processing parameters, e.g., substrate temperature and precursor flow rates, to achieve crystalline SiC without the need for a subsequent annealing step. [Means for solving the problem]

[0012] In one embodiment of the present disclosure, a method for producing as-deposited SiC thin films containing 1 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber comprises: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 600°C to about 1000°C; and providing a precursor comprising a silahydrocarbon, wherein all carbon atoms in the silahydrocarbon are bonded to two silicon atoms, and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; where: a layer of SiC is formed on the substrate surface by adsorption and decomposition of the precursor; The adsorption and decomposition occurs at the substrate surface without the presence of any other reactive species or co-reactants.

[0013] In another embodiment, the present disclosure provides a method for producing an as-deposited SiC thin film containing 0.2 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, the method comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 700°C to about 1000°C; and providing a precursor comprising a silahydrocarbon, wherein all carbon atoms in the silahydrocarbon are bonded to two silicon atoms, and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; where: a layer of SiC is formed on the substrate surface by adsorption and decomposition of the precursor; The adsorption and decomposition occurs at the substrate surface without the presence of any other reactive species or co-reactants. In another embodiment, the present disclosure provides a method for producing as-deposited SiC:O thin films containing 1 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, the method comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 600°C to about 1000°C; providing a precursor comprising a silahydrocarbon, wherein all carbon atoms in the silahydrocarbon are bonded to two silicon atoms, and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; and simultaneously supplying a reactive oxygen-containing gas, which is a co-reactant, to a reaction zone containing the substrate; where: A layer of SiC:O is formed on the substrate surface by adsorption and decomposition of the precursor.

[0014] Advantageous refinements of the invention, which can be implemented alone or in combination, are defined in the dependent claims.

[0015] In summary, the following embodiments are proposed as being particularly preferred within the scope of the present invention:

[0016] Embodiment 1: A method for producing an as-deposited SiC thin film containing 1 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, the method comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 600°C to about 1000°C; and providing a precursor comprising a silahydrocarbon, wherein all carbon atoms are bonded to two silicon atoms and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; where: a layer of SiC is formed on the substrate surface by adsorption and decomposition of the precursor; The adsorption and decomposition occurs at the substrate surface without the presence of any other reactive species or co-reactants.

[0017] Embodiment 2: The method of the preceding embodiment, wherein the substrate comprises silicon, silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, or tantalum nitride.

[0018] Embodiment 3: The method of any preceding embodiment, wherein the precursor comprises 1,3,5-trisilapentane; 1,3,5,7-tetrasilanonane; tricyclo[3,3,1,13,7]pentasilane; 1,3-disilacyclobutane; 1,3,5-trisilacyclohexane (TSCH); or 1,3,5,7-tetrasilacyclooctane.

[0019] Embodiment 4: The method of any preceding embodiment, wherein the precursor comprises 1,3,5-trisilacyclohexane (TSCH) or 1,3,5,7-tetrasilacyclooctane.

[0020] Embodiment 5: The method of any preceding embodiment, wherein the SiC thin film has a Si:C atomic ratio of about 1:0.98 to 1:1.02.

[0021] Embodiment 6: SiC thin film ~ 2080 cm measured by infrared spectroscopy -1 The integrated area under the Si-H bond peak at ~730 cm is measured by infrared spectroscopy. -1 10. The method of any preceding embodiment, wherein the ratio of the integrated area under the Si—C bond peak to the integrated area under the Si—C bond peak is less than about 1:50.

[0022] Embodiment 7: The method of any preceding embodiment, wherein the substrate is heated to a temperature of about 700°C to about 850°C.

[0023] Embodiment 8: A method for producing an as-deposited SiC thin film containing 0.2 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, the method comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 700°C to about 1000°C; and providing a precursor comprising a silahydrocarbon, wherein all carbon atoms are bonded to two silicon atoms and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; where: a layer of SiC is formed on the substrate surface by adsorption and decomposition of the precursor; The adsorption and decomposition occurs at the substrate surface without the presence of any other reactive species or co-reactants.

[0024] Embodiment 9: The method of the preceding embodiment, wherein the substrate comprises silicon, silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, or tantalum nitride.

[0025] Embodiment 10: The method of any preceding embodiment, wherein the precursor comprises 1,3,5-trisilapentane; 1,3,5,7-tetrasilanonane; tricyclo[3,3,1,13,7]pentasilane; 1,3-disilacyclobutane; 1,3,5-trisilacyclohexane (TSCH); or 1,3,5,7-tetrasilacyclooctane.

[0026] Embodiment 11: The method of any preceding embodiment, wherein the precursor comprises 1,3,5-trisilacyclohexane (TSCH) or 1,3,5,7-tetrasilacyclooctane.

[0027] Embodiment 12: The method of any preceding embodiment, wherein the SiC thin film has a Si:C atomic ratio of about 1:0.98 to 1:1.02.

[0028] Embodiment 13: SiC thin film ~ 2080 cm measured by infrared spectroscopy -1 The integrated area under the Si-H bond peak at ~730 cm is measured by infrared spectroscopy. -1 10. The method of any preceding embodiment, wherein the ratio of the integrated area under the Si—C bond peak to the integrated area under the Si—C bond peak is less than about 1:50.

[0029] Embodiment 14: The method of any preceding embodiment, wherein the substrate is heated to a temperature of about 700°C to about 850°C.

[0030] Embodiment 15: A method for producing an as-deposited SiC:O thin film containing 1 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, the method comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 600°C to about 1000°C; providing a precursor comprising a silahydrocarbon, wherein all carbon atoms are bonded to two silicon atoms, and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; and simultaneously supplying a reactive oxygen-containing gas, which is a co-reactant, to a reaction zone containing the substrate; where: A layer of SiC:O is formed on the substrate surface by adsorption and decomposition of the precursor.

[0031] Embodiment 16: The method of the preceding embodiment, wherein the substrate comprises silicon, silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, or tantalum nitride.

[0032] Embodiment 17: The method of any preceding embodiment, wherein the precursor comprises 1,3,5-trisilapentane; 1,3,5,7-tetrasilanonane; tricyclo[3,3,1,13,7]pentasilane; 1,3-disilacyclobutane; 1,3,5-trisilacyclohexane (TSCH); or 1,3,5,7-tetrasilacyclooctane.

[0033] Embodiment 18: The method of any preceding embodiment, wherein the precursor comprises 1,3,5-trisilacyclohexane (TSCH) or 1,3,5,7-tetrasilacyclooctane.

[0034] Embodiment 19: The method of any preceding embodiment, wherein the substrate is heated to a temperature of about 700°C to about 850°C.

[0035] Embodiment 20: The method of any preceding embodiment, wherein the oxygen-containing gas comprises oxygen, water, ozone, and / or nitrous oxide.

[0036] The following detailed description of preferred embodiments of the invention will be better understood when read in conjunction with the accompanying drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are preferred in the invention. It being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. The drawings are as follows: [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 shows representative XPS profiles of Si and C concentration in SiC versus penetration depth for films deposited at 850° C. according to embodiments of the present disclosure, showing Si:C atomic ratios ranging from 1:0.98 to 1:1.02 (nominal 1:1). [Figure 2] FIG. 2 is a representative high-resolution XPS spectrum of the Si 2p binding energy in SiC for a film deposited at 850° C. according to an embodiment of the present disclosure, corresponding to stoichiometric Si:C. [Figure 3] FIG. 3 is a graph of FTIR absorption coefficient versus wavenumber for SiC deposited at 850° C. and annealed at 1000° C. in accordance with an embodiment of the present disclosure. [Figure 4] FIG. 4 is a graph of FWHM at the FTIR peak for SiC as a function of deposition temperature according to an embodiment of the present disclosure. [Figure 5] FIG. 5 shows the FTIR normalized absorbance coefficients for as-deposited SiC films using TSCH as the Si precursor according to an embodiment of the present disclosure and for annealed SiC films deposited using a baseline (control) Si source precursor. [Figure 6] FIG. 6 shows photoluminescence (PL) measurements for as-deposited SiC films using TSCH as the Si precursor according to an embodiment of the present disclosure and SiC films deposited using a baseline (control) Si source precursor. [Figure 7]FIG. 7 shows the FWHM and peak position of the SiC FTIR peak for SiC materials according to embodiments of the present disclosure and a TMDSB control as a function of substrate temperature. [Figure 8] FIG. 8 is a graph of growth rate as a function of deposition temperature for SiC films at 0.2 Torr according to an embodiment of the present disclosure. [Figure 9] FIG. 9 is a plot of refractive index (n) and absorption coefficient (a) values ​​for SiC films measured by ellipsometry at a wavelength of 500 nm versus substrate temperature according to an embodiment of the present disclosure. [Figure 10] FIG. 10 is a graph of the absorption coefficient for SiC grown at 650° C. starting from TSCH and a control (TMDSB) SiC sample according to an embodiment of the present disclosure. [Figure 11] Figure 11(a) shows FTIR spectra in the extended wavenumber range from 500 to 3000 cm for SiC samples deposited at three different deposition temperatures (650°C, 700°C, and 800°C) according to embodiments of the present disclosure. Figure 11(b) shows a zoom in on the absorption peak around 2090 cm in Figure 11(a), which corresponds to the Si-H stretching mode, to get a better perspective on the magnitude of the Si-H peak. DETAILED DESCRIPTION OF THE INVENTION

[0038] This disclosure relates to a deposition method for producing as-deposited crystalline and amorphous silicon carbide (SiC) thin films and oxygen-containing SiC thin films (SiC:O thin films) that are extremely low in structural and compositional defects, particularly defects associated with variations in silicon carbide from ideal stoichiometry (Si:C=1:1), and substitutional and interstitial defects associated with the presence of hydrogen, and the films produced thereby. Generally, silicon carbide thin films with hydrogen levels of 10 atomic % or less are considered to have "low levels of hydrogen incorporation," and films with hydrogen levels of 1 atomic % or less are considered to be "hydrogen-free" (see, e.g., A. Kleinova et al., "FTIR spectroscopy of silicon carbide thin films prepared by PECVD technology for solar cell application," pp. 111-112). Proc. SPIE 9563, Reliability of Photovoltaic Cells, Modules, Components, and Systems VIII, 95630U (September 2015); see S. Gallis et al “Photoluminescence at 1540 nm from erbium-doped amorphous silicon carbide films” J. Mater. Res., 19(8), 2389-2893, 2004).

[0039] The methods described herein can be used to produce both low-level and hydrogen-free SiC films, as defined above, as well as SiC:O thin films. Consistent with current terminology, a film containing "low levels of hydrogen" means that the film contains 10 atomic % or less hydrogen, "hydrogen-free" means that the film contains 1 atomic % or less hydrogen, and a film with "undetectable" hydrogen content contains 0.2 atomic % or less hydrogen. For purposes of this disclosure, silicon carbide films with undetectable hydrogen can also be understood to mean films having a hydrogen content below the detection limit (estimated to be 0.2 atomic %) of spectroscopy and instrumentation, such as infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS).

[0040] The term "thin film" is well understood in the art and can include films having thicknesses from a few nanometers to a few microns. More specifically, the term "thin film" can be understood to mean a film having a thickness of less than 500 nm, preferably 2-50 nm. The term "as-deposited" will be understood in the art to mean that the film has usable properties immediately after deposition without further processing, such as plasma processing, irradiation, or thermal annealing.

[0041] To produce SiC thin films, the method according to the present disclosure involves providing a silahydrocarbon precursor, as described below, such as the preferred TSCH (1,3,5-trisilacyclohexane), in the vapor phase, with or without a carrier or diluent gas, to a reaction zone containing a heated substrate, whereby adsorption and decomposition of the precursor occur, forming stoichiometric silicon carbide with a Si:C atomic ratio ranging from 1:0.98 to 1:1.02 (nominal 1:1) on the substrate surface without further exposure to any other reactive species or co-reactants. To form SiC:O films, an oxygen source is added to the reaction zone to adjust the doping. Alternatively, the as-deposited SiC thin film can be subsequently reacted or treated with an oxygen source. The grain size and morphology of the SiC and SiC:O films can be adjusted by controlling process parameters, such as substrate temperature and precursor flow rates, without the need for a subsequent annealing step to achieve crystalline films. However, if larger grains or epitaxial phases are desired, annealing may also be performed.

[0042] The deposition techniques described herein overcome the shortcomings of known deposition techniques and enable the growth of high-quality, stoichiometric, as-deposited SiC thin films with less than 1% defects and / or hydrogen without the need for post-deposition annealing, while eliminating the problems associated with current Si and C source precursors and minimizing the number and complexity of current processing conditions, thereby maximizing the safety, effectiveness, and productivity of the process.

[0043] The resulting SiC thin films are highly advantageous for important applications in the semiconductor, energy, optics, and optoelectronic industries. In particular, the presence of extremely low levels of defects and hydrogen in as-deposited SiC thin films makes them ideal for incorporation into optical and photoluminescent devices, where as-deposited SiC tends to contain defects and hydrogen that hinder its optical and photoluminescent performance and requires high-temperature annealing to improve such defects. In contrast, as described herein, the extremely low levels of defects and hydrogen present in as-deposited SiC films allow for fine tuning of the concentration and optical performance of dopants, such as oxygen and erbium, to maximize the optical and photoluminescent performance of the resulting devices and systems.

[0044] The method of the present disclosure uses a class of silicon- and carbon-containing source precursors, carbosilanes, also referred to as silahydrocarbons, in which every carbon atom in the silahydrocarbon is bonded to two silicon atoms, and each silicon atom is further bonded to two or more hydrogen atoms. The silicon to carbon atom ratio in the precursor is preferably in the range of about 1 to 1.5. Examples of precursors include 1,3,5,7-tetrasilanonane; 1,3,5,7-tetrasilacyclooctane; tricyclo[3.3.1.13,7]pentasilane; and 1,3-disilacyclobutane (which are not readily available). Preferred commercially available precursors include 1,3,5-trisilapentane and 1,3,5-trisilacyclohexane (TSCH); most preferred is the commercially available cyclic carbosilane 1,3,5-trisilacyclohexane (TSCH). Unlike silane- or halide-type silicon precursors, e.g., SiH4, Si2H6, and SiCl4, this class of Si precursors contains both silicon and carbon atoms, providing a decomposition route to form stoichiometric SiC without the need for a carbon-containing co-reactant. The chemical structure and bonding arrangement of silahydrocarbon-type precursors, e.g., TSCH, enable their decomposition to yield stoichiometric SiC at lower temperatures than those required for the reaction of silane- or halide-type precursors, e.g., SiH4, Si2H6, and SiCl4, with carbon-containing precursors, e.g., CHCl3, C3H4, C2H2, and CCl4, without the need for a post-deposition annealing step.

[0045] Suitable substrates include, but are not limited to, silicon, which is preferred, as well as silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, tantalum nitride, substrates used in optical and photoluminescent applications, and the like.

[0046] A key aspect of the deposition technique described herein is that the method is based on tightly controlled experimental conditions, including source precursor temperature, substrate temperature, precursor flow rate, precursor partial pressure in the reaction zone, and total process pressure, to ensure that the source precursor decomposition pathway occurs in the surface reaction-limited regime, rather than the mass transport-limited regime. These parameters tightly control the adsorption and decomposition mechanisms of silahydrocarbon-type precursors, optimizing the energetics of ligand removal and hydrogen elimination while maintaining Si-C bond integrity and achieving a 1:1 Si:C ratio in the resulting film.

[0047] In this surface reaction-limited regime, without wishing to be bound by theory, the methods described herein ensure two key processes: (i) an elimination reaction in which Si-C double bond structures "silenes" are formed, followed by (ii) dissociative adsorption of hydrogen from silicon atoms, which, depending on the deposition parameters, particularly the substrate temperature, produces SiC films that can be described as films with low hydrogen content (less than 10 atomic % hydrogen), hydrogen-free (less than 1 atomic % hydrogen), or no detectable hydrogen content (less than 0.5 atomic % hydrogen). Furthermore, the resulting SiC films consist exclusively of simply bridging Si-C bonds, with less than 0.2% variation from a 1:1 Si:C stoichiometry (which can be expressed as a range of 1:0.98 to 1:1.02), regardless of the substrate deposition temperature. These films are in contrast to prior art films in which the SiC matrix exhibited a transition from primarily C-Si to C-C, C-Si, and C-H type bonding, while the silicon evolved from Si-C bonds to Si-C, Si-Si, and Si-H bonds as a function of processing conditions, resulting in SiC films with various temperature-dependent complex bonding configurations including high defect densities and significant hydrogen content.

[0048] "Low hydrogen content" is also measured by infrared spectroscopy, at ~2080 cm -1 The integrated area under the Si-H bond peak at ~730 cm -1"Low hydrogen content" may also be understood to mean a material in which the ratio of the integrated area under the Si-H bond peak to the integrated area under the Si-C bond peak is less than 1:50 using standard spectroscopic techniques. "Low hydrogen content" may also be understood to mean a material in which the ratio of the Si-H bond density to the Si-C bond density as measured by infrared spectroscopy is less than 1:50. Note that these IR absorption peak ratios are merely correlations that indicate an extremely low level of Si-H bonds below the IR detection limit. Alternatively, the ratio of the integrated area under the Si-C bond peak to the integrated area under the Si-H bond peak is less than 1:50 using standard spectroscopic techniques. 3 cm -1 Low levels of hydrogen incorporation (as well as the other defects mentioned above) can be determined by observing the absorption coefficient of undoped SiC:

[0049] In a preferred embodiment, films with 1:1 Si:C stoichiometry and undetectable hydrogen (less than 0.2 atomic %) can be prepared at substrate deposition temperatures above about 700°C and below about 1000°C. In another embodiment, where higher hydrogen content is tolerated but 1:1 Si:C stoichiometry is still required, the process temperature is in the range between about 600°C and about 700°C, which offers advantages in both energy efficiency and reduced device exposure to thermal damage. For example, at a deposition temperature of 650°C, film stoichiometry is maintained while the hydrogen content of the film is detectable at levels estimated to be 0.2-1.0 atomic %. It should be noted that the above ranges are intended to include all temperatures within these ranges, for example, but not limited to, 600° C., 625° C., 650° C., 675° C., 700° C., 725° C., 750° C., 775° C., 800° C., 825° C., 850° C., 875° C., 900° C., 925° C., 950° C., 975° C., and 1000° C. Preferred substrate deposition temperatures are from about 700° C. to about 850° C., for example, 700° C., 725° C., 750° C., 775° C., 800° C., 825° C., and 850° C.

[0050] In one embodiment, aspects of the present disclosure relate to a method for producing as-deposited, hydrogen-free (1 atomic % or less hydrogen) crystalline SiC thin films, comprising: supplying a silahydrocarbon-type precursor, such as TSCH, as described above, in the vapor phase without a carrier gas at a temperature of about 600°C to about 1000°C (preferably about 700°C to about 1000°C) to a reaction zone of a deposition chamber containing a heated substrate as described above, whereby adsorption and decomposition of TSCH or other precursors occurs at the substrate surface to form a layer of SiC on the substrate without the presence of other reactive species or co-reactants. This decomposition process results in as-deposited, hydrogen-free, crystalline SiC films without the need for a post-deposition annealing step. It is also within the scope of the present disclosure to provide a diluting inert, non-reactive gas to the precursor in the vapor phase, as this may provide practical advantages or convenience, although a diluting gas is not required.

[0051] The source temperature of the TSCH or other precursor is maintained between about -25 and about 75°C, more preferably between about 0 and about 25°C. The partial vapor pressure of the precursor in the deposition chamber is maintained between about 10% and about 100% of the total pressure in the reaction zone, more preferably between about 50 and about 90% of the total pressure in the reaction zone, with the remaining partial pressure coming from a diluent gas, if present. In the absence of a diluent gas, the precursor vapor pressure constitutes the total system pressure, and neither a diluent nor a carrier gas is required, as the precursor vapor pressure alone maintains the total system pressure (vacuum). The substrate deposition temperature is maintained between about 600°C and about 1000°C, more preferably between about 700°C and about 850°C. The total pressure in the reaction zone (deposition chamber), also known as the working pressure, is maintained between about 0.1 torr and about 760 torr, more preferably between 0.2 torr and 10 torr. Additionally, the diluent gas flow rate (if used) is maintained between about 10 and about 1000 sccm, more preferably between 50 and 250 sccm.

[0052] The diluent gas, if used, is selected from known inert gases such as helium, neon, argon, and xenon.

[0053] Employing these processing parameters to form SiC films ensures a Si:C stoichiometry of 1:1±0.05, preferably 1:1±0.02 (1:1.098 to 1:1.02), as measured by XPS, and less than 1 atomic percent hydrogen, as measured by infrared spectroscopy. Furthermore, the ratio of the integrated area under the Si-H bond peak at ∼2080 cm-1 for the SiC film, as measured by infrared spectroscopy, to the integrated area under the Si-C bond peak at ∼730 cm-1, as measured by infrared spectroscopy, is less than about 1:50.

[0054] In another embodiment, aspects of the present disclosure relate to a method for producing as-deposited crystalline SiC films with undetectable concentrations (0.2 atomic % or less) of H (both interstitial and substitutional) and defects. The method includes providing TSCH or another silahydrocarbon-type precursor described above in the vapor phase at a temperature of about 700°C to about 1000°C (preferably about 700°C to about 850°C) to a reaction zone of a deposition chamber containing a heated substrate, as described above, whereby adsorption and decomposition of TSCH or another precursor occurs on the substrate surface in the presence of a diluting inert, non-reactive gas, resulting in the formation of a layer of SiC on the substrate in the absence of other reactive species or co-reactants. This decomposition process results in as-deposited crystalline SiC films with undetectable concentrations of H (both interstitial and substitutional) and defects, as described above, without the need for a post-deposition annealing step. It is also within the scope of the present disclosure to provide a diluting inert, non-reactive gas with the precursor in the vapor phase, as this may provide practical advantages or convenience, although a diluting gas is not required.

[0055] The source temperature of the TSCH or other precursor is maintained between about -25 and about 75°C, more preferably between about 0 and about 25°C. The partial vapor pressure of the precursor in the deposition chamber is maintained between about 10% and about 100% of the total pressure in the reaction zone, more preferably between about 50 and about 90% of the total pressure in the reaction zone, with the remaining partial pressure coming from a diluent gas, if present. In the absence of a diluent gas, the precursor vapor pressure constitutes the total system pressure, and neither a diluent nor a carrier gas is required, as the precursor vapor pressure alone maintains the total system pressure (vacuum). The substrate deposition temperature is maintained between about 700°C and about 1000°C, more preferably between about 700°C and about 850°C. The total pressure in the reaction zone (deposition chamber), also known as the working pressure, is maintained between about 0.1 torr and about 760 torr, more preferably between 0.2 torr and 10 torr. Additionally, the diluent gas flow rate (if used) is maintained between about 10 and about 1000 sccm, more preferably between 50 and 250 sccm.

[0056] The diluent gas, if used, is selected from known inert gases such as helium, neon, argon, and xenon.

[0057] Employing these processing parameters to form SiC films ensures a Si:C stoichiometry of 1:1±0.05, preferably 1:1±0.02 (1:1.098 to 1:1.02), and less than 1 atomic percent hydrogen. Furthermore, the ratio of the integrated area under the Si-H bond peak at ∼2080 cm-1 for the SiC film as measured by infrared spectroscopy to the integrated area under the Si-C bond peak at ∼730 cm-1 as measured by infrared spectroscopy is less than about 1:50.

[0058] In a further embodiment, aspects of the present disclosure relate to a method for producing as-deposited SiC:O films containing 1 atomic % or less of hydrogen. The method includes providing TSCH (or other precursors as defined above) in the vapor phase, without a carrier or diluent gas, at a temperature of about 600°C to about 1000°C (preferably about 700°C to about 850°C) to a reaction zone of a deposition chamber containing a heated substrate as described above, while simultaneously introducing an oxygen-containing gas into the reaction zone of the deposition chamber, thereby causing adsorption and decomposition of TSCH on the substrate surface in the presence of a reactive oxygen-containing gas as a co-reactant, to form a SiC:O layer on the substrate surface. It is also within the scope of the present disclosure to provide a diluting inert, non-reactive gas to the precursor in the vapor phase, as this may provide practical advantages or convenience, although a diluting gas is not required. The decomposition process results in an as-deposited hydrogen-free SiC:O film, i.e., a film containing 1 atomic % or less of hydrogen.

[0059] The source temperature of TSCH or other precursor is maintained between about -25 and about 75°C, more preferably between about 0 and about 25°C, and the partial vapor pressure of TSCH in the deposition chamber is maintained between about 10% and about 100% of the total pressure in the reaction zone, more preferably between about 50 and about 90% of the total pressure in the reaction zone. The oxygen-containing gas co-reactant flow rate is set to achieve a corresponding partial vapor pressure in the reaction zone of between about 1% and about 25% of the carbosilane precursor, more preferably between about 5% and about 10% of the carbosilane precursor. The substrate deposition temperature is maintained between about 600°C and about 1000°C, more preferably between about 700°C and about 850°C. The total pressure, also referred to as the working pressure, of the reaction zone (deposition chamber) is maintained between about 0.1 torr and about 760 torr, more preferably between 0.2 torr and 10 torr. Additionally, the diluent gas flow rate (if used) is maintained between about 10 and about 1000 sccm, more preferably between 50 and 250 sccm.

[0060] The diluent gas, if used, is selected from known inert gases such as helium, neon, argon, and xenon. The oxygen-containing gas co-reactant is selected from the group consisting of oxygen, water, ozone, nitrous oxide, and other typical oxygen-containing reactants known in the art.

[0061] Alternatively, the as-deposited SiC film can then be treated in-situ (before removal from the deposition chamber) or ex-situ (by removal from the deposition chamber and placing in a furnace or annealing chamber) by exposure to an oxygen-containing source to form a SiC:O film.

[0062] It is also within the scope of the present disclosure to replace some or all of the hydrogen atoms bonded to silicon atoms in the precursor with deuterium atoms. -1 Deuterium offers the advantage of eliminating substitutional defects associated with Si-H bond infrared absorption in the range of 1000 sq ft (1000 sq m), and deuterium is less prone than hydrogen to cause hydrogen-related dislocations in amorphous silicon and silicon carbide systems, further reducing the overall concentration of interstitial defects (if they exist). In the case of trisilacyclohexane, all six hydrogen atoms are replaced with deuterium atoms. This compound is readily prepared by utilizing lithium aluminum deuteride to reduce a hexaalkoxyltrisilacyclohexane intermediate. As another example, the eight silicon-bonded hydrogen atoms in trisilapentane can be replaced with deuterium in a similar manner.

[0063] The present invention will now be described with reference to the following non-limiting examples, which illustrate the deposition of stoichiometric SiC films on Si substrates with extremely low defect and hydrogen levels starting from TSCH (1,3,5-trisilacyclohexane).

[0064] Example 1: Identification of optimized process window Six stoichiometric SiC films were produced by decomposition of TSCH (1,3,5-trisilacyclohexane) on Si substrates using the processing parameters summarized in Table I .

[0065] [Table 1]

[0066] The obtained films were analyzed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) measurements.

[0067] The Si and C concentrations versus penetration depth in SiC films were evaluated by XPS depth profile analysis, as shown in Figures 1 and 2, for as-deposited SiC films grown at a substrate temperature of 850 °C. Similar data was obtained for runs 2, 3, and 6, demonstrating the robustness of the deposition process. The data show a consistent 1:1 Si:C atomic ratio throughout the film, with a precision ranging from 1:0.98 to 1:1.02, proving that the films are stoichiometric. High-resolution XPS spectra for the Si 2p binding energy are displayed in Figure 8 for SiC films deposited at 800 °C; both runs 1 and 5 (different thicknesses) yielded identical XPS spectra. The Si 2p binding energy position of 100.3 eV confirms that the chemical bond corresponds to Si-C (standard use: 3C-SiC).

[0068] FTIR analysis shows that: (i) the peak at 800 cm as shown in Figure 3; -1 A single strong absorption peak was observed around 62.0–49.8 cm , which corresponds to the Si–C stretching mode of crystalline SiC. The FWHM of this FTIR peak was 62.0–49.8 cm after annealing at 1000 °C for 1 h. -1 (ii) As shown in Figure 4, the FWHM of the FTIR peaks decreases with increasing deposition temperature, suggesting that deposition crystallinity increases with increasing deposition temperature.

[0069] Example 2: Investigation of processing parameters and precursor chemistry Ten stoichiometric SiC films according to the present invention were fabricated by decomposition of TSCH (1,3,5-trisilacyclohexane) on Si substrates, and two comparative SiC films (7th and 14th) were fabricated as controls by decomposition of TMDSB (1,1,3,3-tetramethyl-1,3-disilacyclobutane) as a precursor on Si substrates. The processing parameters are summarized in Table II below.

[0070] [Table 2]

[0071] Figure 5 displays a comparison of crystallinity between annealed SiC films deposited using the baseline source precursor as a control and as-deposited SiC films using TSCH as the precursor. FTIR spectra show that the as-deposited SiC film using the TSCH precursor exhibits 100% crystallinity after annealing at 1100 °C, similar to the SiC film deposited starting from the baseline Si source precursor. It is noteworthy that no deposition occurs for the baseline precursor TMDSB below 800 °C, and the as-deposited SiC starting from the comparative material incorporates high levels of H (over 11 atomic %) and defects.

[0072] Photoluminescence (PL) measurements for SiC films deposited using the baseline TMDSB control precursor and SiC films using TSCH as a precursor are shown in Figure 6. The SiC films using TSCH as a precursor exhibited no or negligible PL intensity, indicating a significant reduction in defect density compared to the SiC films deposited using the baseline (TMDSB) Si source precursor.

[0073] Figure 7 is a graph of the peak position and FWHM of the SiC FTIR peak for the TMDSB control and TSCH samples of the present invention as a function of substrate temperature. With increasing substrate temperature, the FWHM and red-shifted peak position decrease, indicating higher crystallinity at higher deposition temperatures.

[0074] The growth rate as a function of deposition temperature at 0.2 Torr is also shown in Figure 8. The highest growth rate observed was 2.23 nm / s at 850 °C. As expected, the growth rate decreases with decreasing substrate temperature due to the decrease in thermal energy available for the precursor decomposition reaction.

[0075] Representative atomic force microscope (AFM) micrographs of SiC samples were measured as a function of substrate temperature (not shown). The root-mean-square (rms) surface roughness increased with increasing substrate temperature. This result is as expected and is attributed to higher crystallinity at higher substrate temperatures.

[0076] Scanning electron microscopy (SEM) results (not shown) for substrate temperatures of 800°C, 700°C, and 650°C showed good correlation with the AFM data in terms of rms surface roughness, which increased with increasing substrate temperature.

[0077] The refractive index (n) and absorption coefficient (a) values ​​for the SiC films determined by ellipsometry at a wavelength of 500 nm are plotted against deposition temperature in Figure 9, where n values ​​are represented by circles and a values ​​by triangles. The refractive index n varied between 2.9 and 2.7 for all deposition temperatures, which is consistent with the reference value for 3C-SiC (2.7), indicating a stoichiometric SiC phase.

[0078] Furthermore, a comparison of the absorption coefficients for SiC grown at 650 °C using TSCH and the control TMDSB SiC sample is shown in Figure 10. The TSCH SiC film shows a dramatic reduction in absorption in the visible region, in stark contrast to the control SiC sample, which shows high absorption across the entire energy range. This clearly indicates that the defect density in SiC grown at 650 °C using TSCH is significantly lower than that of the control SiC sample.

[0079] Finally, Figure 11(a) shows the 500–3000 cm -1 Figure 1 illustrates FTIR spectra for SiC samples of the present invention deposited at three different temperatures (650°C, 700°C, and 800°C) over an extended wavenumber range of 1000 to 15000 cm. The FTIR spectra show: (i) a 800 cm peak at 1500 cm, which corresponds to the Si-C stretching mode of crystalline SiC; -1 (ii) a single very strong absorption peak near 2090 cm corresponding to the Si–H stretching mode for the sample grown at 650 °C. -1 The Si-H peak is reduced to below the background signal for the samples deposited at 700 °C and 800 °C, indicating that H in the SiC samples is below the detection limit of FTIR. Figure 11(b) shows the absorption peak at 2090 cm corresponding to the Si-H stretching mode. -1 The absorption peaks in the vicinity are enlarged to allow for a more accurate understanding of the magnitude of the Si-H peak.

[0080] Those skilled in the art will appreciate that changes could be made in the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that the invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the invention as defined by the appended claims.

Claims

1. 1. A method for producing as-deposited SiC thin films containing 1 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 600°C to about 1000°C; and providing a precursor comprising a silahydrocarbon, wherein all carbon atoms are bonded to two silicon atoms and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; where: a layer of SiC is formed on the substrate surface by adsorption and decomposition of the precursor; A method wherein said adsorption and decomposition occurs at the substrate surface in the absence of any other reactive species or co-reactants.

2. The method of claim 1 , wherein the substrate comprises silicon, silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, or tantalum nitride.

3. 3. The method of claim 1 or 2, wherein the precursor comprises 1,3,5-trisilapentane; 1,3,5,7-tetrasilanonane; tricyclo[3,3,1,13,7]pentasilane; 1,3-disilacyclobutane; 1,3,5-trisilacyclohexane (TSCH); or 1,3,5,7-tetrasilacyclooctane.

4. 4. The method of claim 1, wherein the precursor comprises 1,3,5-trisilacyclohexane (TSCH) or 1,3,5,7-tetrasilacyclooctane.

5. 5. The method of claim 1, wherein the SiC thin film has a Si:C atomic ratio of about 1:0.98 to 1:1.

02.

6. ∼2080 cm of SiC thin film measured by infrared spectroscopy -1 The integrated area under the Si-H bond peak at ∼730 cm was measured by infrared spectroscopy. -1 7. The method of claim 1, wherein the ratio of the integrated area under the Si-C bond peak to the integrated area under the Si-C bond peak is less than about 1:

50.

7. The method of any one of claims 1 to 6, wherein the substrate is heated to a temperature of about 700°C to about 850°C.

8. 1. A method for producing an as-deposited SiC thin film containing 0.2 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 700°C to about 1000°C; and providing a precursor comprising a silahydrocarbon, wherein all carbon atoms are bonded to two silicon atoms and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; where: a layer of SiC is formed on the substrate surface by adsorption and decomposition of the precursor; A method wherein said adsorption and decomposition occurs at the substrate surface in the absence of any other reactive species or co-reactants.

9. 9. The method of claim 8, wherein the substrate comprises silicon, silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, or tantalum nitride.

10. 10. The method of any one of claims 1 to 9, wherein the precursor comprises 1,3,5-trisilapentane; 1,3,5,7-tetrasilanonane; tricyclo[3,3,1,13,7]pentasilane; 1,3-disilacyclobutane; 1,3,5-trisilacyclohexane (TSCH); or 1,3,5,7-tetrasilacyclooctane.

11. 11. The method of any one of claims 1 to 10, wherein the precursor comprises 1,3,5-trisilacyclohexane (TSCH) or 1,3,5,7-tetrasilacyclooctane.

12. 12. The method of claim 1, wherein the SiC thin film has a Si:C atomic ratio of about 1:0.98 to 1:1.

02.

13. ∼2080 cm of SiC thin film measured by infrared spectroscopy -1 The integrated area under the Si-H bond peak at ∼730 cm was measured by infrared spectroscopy. -1 13. The method of claim 1, wherein the ratio of the integrated area under the Si-C bond peak to the integrated area under the Si-C bond peak is less than about 1:

50.

14. The method of any one of claims 1 to 13, wherein the substrate is heated to a temperature of about 700°C to about 850°C.

15. 1. A method for producing as-deposited SiC:O thin films containing 1 atomic % or less hydrogen on a substrate in a reaction zone of a deposition chamber, comprising: providing a substrate in a reaction zone of a deposition chamber; heating the substrate to a temperature of about 600°C to about 1000°C; providing a precursor comprising a silahydrocarbon, wherein all carbon atoms are bonded to two silicon atoms, and each silicon atom is further bonded to two or more hydrogen atoms, in the vapor phase without a carrier gas to a reaction zone containing a substrate; and simultaneously supplying a reactive oxygen-containing gas, which is a co-reactant, to a reaction zone containing the substrate; where: A method in which a layer of SiC:O is formed on the substrate surface by adsorption and decomposition of said precursor.

16. 16. The method of claim 15, wherein the substrate comprises silicon, silicon oxide, silicon nitride, silicon carbide, gallium nitride, cobalt, ruthenium, copper, platinum, titanium, titanium nitride, tantalum, or tantalum nitride.

17. 17. The method of any one of claims 1 to 16, wherein the precursor comprises 1,3,5-trisilapentane; 1,3,5,7-tetrasilanonane; tricyclo[3,3,1,13,7]pentasilane; 1,3-disilacyclobutane; 1,3,5-trisilacyclohexane (TSCH); or 1,3,5,7-tetrasilacyclooctane.

18. 18. The method of any one of claims 1 to 17, wherein the precursor comprises 1,3,5-trisilacyclohexane (TSCH) or 1,3,5,7-tetrasilacyclooctane.

19. The method of any one of claims 1 to 18, wherein the substrate is heated to a temperature of about 700°C to about 850°C.

20. 20. The method of any one of claims 1 to 19, wherein the oxygen-containing gas comprises oxygen, water, ozone, and / or nitrous oxide.

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