Gas Mixture Of SiH4 Research Articles

Particle formation in SiOx film deposition by low frequency plasma enhanced chemical vapor deposition

Dust particle formation dynamics in the process of SiOx film deposition from a SiH4 and N2O gas mixture by a low frequency plasma enhanced chemical vapor deposition have been investigated using scanning electron microscopy and laser light scattering. The deposited films are confirmed to be SiOx from the measurements of Auger electron spectroscopy, x-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. It is observed by scanning electron microscopy that particles are deposited on Si substrate at the plasma power frequency f=5 kHz and above both with and without substrate heating (400 °C), while no particle is deposited below f=1 kHz. Moreover, the laser light scattering indicates that particles are generated at the plasma power frequency of f=3 kHz and above in the gas phase, and that they are not generated in the gas phase at below f=3 kHz. Properties (the refractive index, resistivity, and Vickers hardness) of the films with particles are inferior to those of the films without particles. This article has revealed experimentally the effect of plasma power frequency on SiOx particle formation and makes a contribution to the explication of the particle formation mechanism. We suggest that high-quality film deposition with the low frequency plasma enhanced chemical vapor deposition method is attained at f=1 kHz or less without substrate heating.

Silicon Oxynitride Waveguides for Optoelectronic Integrated Circuits

Planar optical waveguides on p-type Si wafers have been fabricated by a photo-induced deposition process. Silicon oxynitride was deposited using a gaseous mixture of SiH4 (2% in Ar), NH3 and N2O under 253.7 nm UV radiation. The oxynitride composition was varied by changing N2O: ( N2O+NH3) ratio while keeping N2O+NH3 and SiH4 flow rates constant. The refractive index varied from 1.46 to 1.95. The optical energy gap increased from 4.8 to 5.7 as the flow rate ratio varied from 0 to 0.25. Si–N bond shifts to higher energy owing to the incorporation of oxygen. A planar waveguide structure was fabricated using thermally grown SiO2 buffer layer of 1.1 µ m thickness. The loss was estimated to be 1.1 dB/cm for TE0 mode at 632.8 nm. The accuracy of measurements is 0.02 dB/cm.

Analysis of H2-Dilution Effects on Photochemical Vapor Deposition of Si Thin Films

Hg-sensitized photochemical vapor deposition (photo-CVD) of Si thin films at low temperatures using a gas mixture of SiH4 and H2 was analyzed and the concentrations of SiH3 and H in the gas phase were theoretically estimated. The results of the calculation were compared with the properties of the Si thin films, and the roles of atomic H were discussed. With the correlations between the radical concentrations near the growing surface and film properties such as film structure, film quality, and the concentration of bonded hydrogen in a-Si films were successfully explained. It is suggested that the roles of atomic H on the growing surface are a termination of dangling bonds on the surface and an extraction of SiH3 radicals from the growing surface. Since the role of atomic H competes with the deposition of Si, the supply balance between the atomic H and the SiH3 radicals is essential to determine the properties of Si thin films.

Correlation between the optoelectronic properties and the structure of hydrogenated amorphous silicon-carbon films grown from a C2H2 gas source

Abstract Hydrogenated amorphous silicon-carbon alloys (a-Si1−x-Cx:H) with an optical gap in the range 2.0–2.45eV have been grown by plasma-enhanced chemical vapour deposition from C2H2 + SiH4 gas mixtures employing low-purity (99.95%) sources. By changing the acetylene percentage in the plasma from 0.8% to 20% the relative carbon content [C]/[C + Si] in the films was varied between 0.09 and 0.35, as deduced from Rutherford back scattering. Optical, electrical and defect data have been obtained. We have shown that the physical properties of C2H2 based films, without any deposition condition optimization, are comparable with high-electronic-quality CH4-based samples at the same optical gap. The network structure of C2H2 based films differs from CH4 based films, as revealed by infrared spectroscopy.

Photo and Thermal Stability of Chlorine Doped Amorphous Silicon TFTs

ABSTRACTThe Cl doped amorphous silicon film was deposited from SiH4, SiH2C12 and H2 gas mixture by PECVD process and their properties with various SiH2C12 flow rate is discussed. Controlling the amount of Cl doped was crucial for acquiring high stability TFT without lowering on current. Amorphous silicon and Cl doped amorphous silicon double layer TFT structure, with satisfactory on current and throughput, proved to be more stable than conventional amorphous silicon TFT in photo state and in elevated temperatures.

Silicon oxide thin films prepared by a photo-chemical vapour deposition technique

Wide band gap a-SiOx:H films have been prepared by the photochemical decomposition of a SiH4, CO2 and H2 gas mixture. Deposition parameters namely the CO2 to SiH4 gas flow ratio, H2 dilution and chamber pressure were optimized in order to achieve highly photoconducting (1 × 10-6 S cm-1) films with an optical gap of 1.99 eV. The optical gap was found to increase with an increase in the CO2 to SiH4 flow ratio. A decrease in the photoconductivity, refractive index, spin g-value and a simultaneous increase in the spin density are attributed to an incorporation of oxygen into the films. Upon hydrogen dilution the photoconductivity of a-SiOx:H films was observed to improve along with an increase of the optical gap. The spin density of a-SiOx:H films was of the order of 1017 cm-9. The optoelectronic properties of the films have been correlated with the bonding configurations in the film, deposition parameters and the growth kinetics.

Optically Addressed Spatial Light Modulator with Highly Sensitive Layer of Amorphous Hydrogenated Silicon Carbide

Abstract The photoaddressed spatial light modulator (PLSM) with thin hydrogenated amorphous silicon carbide photoreceptor α-Si1−XCx:H and nematic liquid crystal has been fabricated. The films were prepared by rf plasma decomposition of SiH4 and CH4 gas mixture. They have a high dark resistivity and photosensitivity as a hydrogenated amorphous silicon, but a more transmittance in visible spectrum. The maximum of diffraction efficiency for PLSM was achieved for the write light intensity 40 μW/cm2, a resolution on the one half of maximum of diffraction efficiency was 54 mm−1. The optical response of PLSM was observed in the frequency region from 1 Hz to 100 Hz.

New Silicon-Carbon Materials Incorporating Si4C Building Blocks

AbstractNovel precursor chemistry and ultrahigh-vacuum chemical vapor deposition have been used to deposit Si1-yCyth in films on (001) Si substrates. Films with carbon compositions ranging up to 20 at. % were deposited at substrate temperatures of 600–750°C using interactions of C(SiH3)4 or C(SiH2Cl)4 (C-H free precursors incorporating Si4C tetrahedra) and SiH4 gas mixtures. The composition of the resulting materials was obtained by Rutherford backscattering spectrometry including carbon resonance analysis. Cross-sectional transmission electron microscopy and infrared spectroscopy were used to provide microstructural and bonding information respectively. The effect of precursor chemistry on the composition and structure of the materials is discussed.

Material Properties of Sipos Films Prepared by XeCl Excimer Laser Annealing of a-Si:Nx Films

AbstractThe material properties of laser-annealed a-Si:Nx films were investigated. The a-Si:Nx films for laser-annealing were deposited by rf plasma enhanced chemical vapor deposition (PECVD) with NH3 and SiH4 gas mixtures. At the 0.35 of NH3/SiH4 ratio, the optical band-gap was abruptly increased to 2.82 eV from 2.05 eV by laser-annealing which indicates that Si-N bonding comes to be notable at that ratio. The electrical conductivity showed the maximum value of 4× 10-6 S/cm at the 0.11 of NH3/SiH4 ratio where the grain growth and the increase of Si-N bonding are optimized for the enhancement of electrical conductivity. The σP/σD ratio which is related to the defects states for photo generation centers was decreased with increasing NH 3/SiH 4 ratio. Our experimental data showed that the optical band gap and electrical conductivity of laserannealed a-Si:Nx films were dominantly affected by the NH3/SiH4 ratio at the 250 mJ/cm2 of laser-annealing energy density.

Low-Temperature Formation of Device-Quality Polysilicon Films by cat-CVD Method

AbstractPolycrystalline silicon (poly-Si) films are deposited at temperatures lower than 300–400°C by the cat-CVD method. In the method, a SiH4 and H2 gas-mixture is decomposed by catalytic cracking reactions with a heated tungsten catalyzer placed near substrates. Carrier transport, optical and structural properties are investigated for this cat-CVD poly-Si. The films show both large carrier mobility and large optical absorption for particular deposition conditions. The cat-CVD poly-Si films are found to be one of the useful materials for thin film transistors and thin film solar cells.

Low temperature deposition of silicon nitride films by distributed electron cyclotron resonance plasma-enhanced chemical vapor deposition

Silicon nitride thin films have been deposited via distributed electron cyclotron resonance plasma-enhanced chemical vapor deposition, without intentional substrate heating, using SiH4 and N2 gas mixtures. The effects of N2/SiH4 gas flow (1.5–19) and microwave power (800–1500 W) on deposition rate, refractive index, composition, chemical bonds, and etch rate were studied by ellipsometry, MeV ion beam analysis techniques, and Fourier transform infrared spectroscopy. All parameters examined indicate that a highly diluted SiH4 gas phase and a microwave power of 1500 W help to prepare quasistoichiometric films with a high density (2.9 g/cm3) and a refractive index of 1.98. The effects of film density and film stoichiometry (N/Si) on refractive index are discussed through the Lorentz–Lorenz relation. The first electric results show that, under the optimized deposition parameters, a critical field of 2.3 MV/cm and an interface state density of 5×1010 eV−1 cm−2 can be achieved.

Effect of Plasma Damage on Interface State Density Between a-Si:H and Insulating Films

ABSTRACTThe interface state density between a-Si:H and insulating film is very important in characteristics of a-Si:H thin film transistors. In this study, the interface state density was measured by photothermal deflection spectroscopy (PDS). Layered structures of a-SiN, 1.7:H on a-Si:H and a-SiO2.0 on a-Si:H were deposited by P-CVD method. The a-SiN1.7:H layer was grown from a gas mixture of SiH4 and NH3 and the a-SiO2.0 layer was grown from a gas mixture of SiH4 and N2O. While the interface state density of a-SiN1.7:H on a-Si:H structure was smaller than the free surface state density of a-Si:H, that of a-SiO2.0 on a-Si:H structure was larger than the free surface state density of a-Si:H. The difference in the surface state density between these specimens is discussed in terms of plasma damage of a-Si:H surface by the source gases during deposition of insulating layer. Surface of the a-Si:H was treated by plasma of NH3 or N2o gas which is dominant constituent of source gases of insulating layer. Although the surface state density of the N2o plasma-treated sample increases, that of NH3 plasma treated sample does not increase. The shape and intensity of the spectra of N2o plasma-treated sample is similar to that of the a-Sio2.0 on a-Si:H structure. These results indicate that the interface defect between a-Sio2.0and a-Si:H layer was induced by plasma damage of the a-Si:H surface.

Self-propagating chain combustion with formation of ultradispersed powders

We have investigated the possibility of realizing the self-propagating combustion regime for a gaseous mixture of SiH4−NH3−O2 and SiH4-2 with an oxygen content of 0–2%. Calculation of the equilibrium composition indicates the possibility that the target products Si and Si3N4 are formed. We have established experimentally that propagation of the chemical reaction front in the self-sustaining regime with formation of the above-indicated products occurs only in the presence of oxygen. We show that chemical induction, leading to consumption of up to 60% of the initial monosilane, is a chain reaction.

Relationships between the material properties of silicon oxide films deposited by electron cyclotron resonance chemical vapor deposition and their use as an indicator of the dielectric constant

Silicon dioxide films deposited by electron cyclotron resonance chemical vapor deposition have been characterized using Fourier transform infrared spectroscopy, Rutherford backscattering spectrometry, and ellipsometry. A commercially available reactor was used to generate a high-density plasma at low total gas pressures (3–4 mTorr). A gas mixture of Ar, O2, and SiH4 was used to deposit SiO2 films on 200 mm Si substrates at temperatures less than 450 °C for interlayer dielectric applications. The dielectric constant of the films was measured using metal oxide semiconductor capacitors. Relationships between the dielectric constant and the refractive index, Si–OH content, and film stoichiometry were investigated using a model based on the Clausius–Mosotti equation. During the study, the O2 and SiH4 gas flows were adjusted to vary the film properties. Silicon dioxide was deposited over a wide range of O2 and SiH4 gas flow conditions. For SiO2 films, the dielectric constant was strongly correlated with the Si–OH content. At low O2/SiH4 gas flow ratios, suboxide films were deposited and the dielectric constant increased in relation to the refractive index. A low-temperature, postdeposition anneal was investigated as a means to reduce the Si–OH content and dielectric constant of the films. Modeling results indicate that the dielectric constant of SiO2 films can be predicted using measurements of the film thickness, refractive index, and Si–OH content, thus providing a nondestructive technique for monitoring the dielectric constant.

Improvement of film Quality of A-Si:H Deposited by Photo-CVD using SiH2Cl2

ABSTRACTHydrogenated Amorphous silicon films (a-Si:H) were prepared by mercury sensitized photo-CVD using SiH4 and SiH2Cl2 gas mixture. The effects of chlorine (Cl) on the electrical, optical and structural properties of the a-Si:H films were investigated. It was found that a small addition of SiH2Cl2 to the deposition system increases the photo-sensitivity, decreases the defect density, and reduces the light induced degradation of a-Si:H films. At a large addition of SiH2Cl2, however, the CI incorporation into the films was observed, resulting in the deterioration of the film properties. The electrical and optical properties were successfully improved by the H2 dilution when the films were deposited with a large addition of SiH2Cl2.

Structure of high-photosensitivity silicon-oxygen alloy films

Amorphous silicon-oxygen alloy films with various composition have been prepared by r.f. glow discharge decomposition of SiH4 and CO2 gas mixtures. The analysis of infrared absorption spectra and x-ray photoemission spectra shows that the film consists of two phases, a silicon-rich phase and an oxygen-rich phase. We suggest that this two-phase structure results in the high photoconductivity with wide optical gap in these films.

Diode laser induced chemical vapor deposition of WSix on TiN from WF6 and SiH4

A compact and inexpensive laser direct writing system, using a continuous wave GaAlAs diode laser array emitting 1 W at λ=796 nm, has been developed for the deposition of WSix on TiN from a gas mixture of WF6 and SiH4. Lines 4 to 15 μm wide and 110–950 nm thick are deposited at 5 μm/s in a static reactor. The W/Si ratio in the bulk of the deposit, as measured by Auger electron spectroscopy, is between 1.1 and 1.4 for the lines deposited from a gas mixture of 1 Torr WF6 and 3 Torr/SiH4. In a dynamic reactor, with a flowing gas mixture of 1 sccm WF6 and 3 sccm SiH4 diluted in 50–150 sccm Ar, lines written at 100 μm/s are typically 4–12 μm wide and 250–800 nm thick. The W/Si ratio in the bulk of the deposit is between 1.5 and 1.8 in this case. Thickness decreases when the argon flow increases suggesting that the growth rate is limited by the transport of the reactive species, at least for a portion of the growth. A tungsten-rich top surface of the deposited layer is also observed, indicating that room temperature reactions, between the gas species and the deposited materials, continue after the deposition.

Defect Evaluation of Heavily P-Doped Si Epitaxial Films Grown at Low Temperature

Heavily P-doped epitaxial Si films with carrier concentration of 3×1021 cm-3 have been successfully grown by plasma chemical vapor deposition using a gas mixture of SiH4, SiF4, H2 and PH3 at a very low temperature of 250°C. From the annealing characteristics of heavily P-doped Si films, it was found that the electron concentration decreased once after annealing at 600°C but increased subsequently upon raising the annealing temperature. The possibility of the formation of a vacancy-type defect complex, typically (v-P4), a vacancy surrounded by four phosphorus atoms, was proposed to interpret this phenomenon. Furthermore, a positron annihilation experiment was employed to investigate this vacancy-type defect in Si films and good agreement was obtained between thermodynamical calculation based on the v-P4 model and the positron annihilation experiment.

Dépôt par laser de WSix sur du TiN à partir de WF6 et de SiH4

A direct writing system has been developed for the deposition of WSix on TiN from a gas mixture of WF6 and SiH4. An Ar+ (488 nm, 1.5 W) and a diode laser (796 nm, 1.0 W) are used as the photon source. Lines are written at scan speeds of up to 100 μm s−1 from a flowing gas mixture of WF6 and SiH4 diluted in Ar. Deposits of 1.5 to 11 μm wide and 20 to 180 nm thick are obtained at a writing speed of 100 μm s−1 with the Ar+ laser. Lines written using the diode laser are typically 4 to 12 μm wide and 160 to 860 nm thick. The W/Si ratio in the deposit is between 1.5–1.8 for a mixture of 1 sccm WF6 and 3 sccm SiH4 diluted in 50 to 150 sccm Ar.

Crystallization and sintering characteristics of chemically vapor deposited silicon nitride powders

High purity silicon nitride powders have been obtained by Chemical Vapor Deposition (CVD), through the reaction of SiH4 and NH3 gas mixtures at 1000 °C in a quartz reactor. The crystallization characteristics of the powder have been followed by infrared and x-ray diffraction analysis. The material shows a transition from amorphous to the α-phase after a thermal treatment at about 1300 °C for 1 h, while the β-phase starts to appear at 1725 °C. The sintering properties of the amorphous and crystalline phases were evaluated by measuring the dilatometric curves of compacted powders.