Mixture Of SiH4 Research Articles

Effect of deposition temperature on the bonding configurations and properties of fluorine doped silicon oxide film

In our study, fluorine-doped silicon oxide (SiOF) films were prepared using a mixture of SiH 4, N 2O, and CF 4 in a conventional plasma enhanced chemical vapor deposition system at various deposition temperatures. Deposition behaviors are determined by the deposition temperature. Our results show that for temperatures below 300 °C the process is surface-reaction-limited controlled, but becomes diffusion-limited when the deposition temperature exceeds 300 °C. The surface topography images obtained using an atomic force microscope show that a large amount of free volume space was created in the film with a low temperature deposition. The optical microscope and secondary ion mass spectrometer analyses show that precipitates were produced at the near-surface at the deposition temperature of 150 °C with a higher fluorine concentration of 2.97 at.%. Our results show that the properties of the SiOF film are controlled not only by the free volume space but also by the fluorine concentration. An optimal SiOF film prepared at a temperature of 200 °C shows a low dielectric constant of 3.55, a leakage current of 1.21 × 10 − 8 A/cm 2 at 1 MV/cm, and a fluorine concentration of 2.5 at.%.

Suppression of Electrical Breakdown in Silicon Nitride Films Deposited by Catalytic Chemical Vapor Deposition at Temperatures Below 200 °C

Silicon nitride (SiN(x)) films for a gate dielectric layer of thin film transistors were deposited by catalytic chemical vapor deposition at a low temperature (< or = 200 degrees C). A mixture of SiH4, NH3 and H2 was used as a source gas. Metal-insulator-semiconductor (MIS) capacitor structures were fabricated for current-voltage (I-V) and capacitance-voltage (C-V) measurements. The breakdown voltage characteristics of the SiN(x) films were improved by the increase of NH3/SiH4 and H2/SiH4 mixing ratios and substrate temperatures. H2 treatment was attempted to improve the breakdown voltage further. A breakdown voltage as high as 6.6 MV/cm was obtained after H2 annealing at 180 degrees C. The defect states inside the SiN(x) films were analyzed by photoluminescence spectra. Silicon dangling bonds (2.5 eV) and nitrogen dangling bonds (3.1 eV) were observed. These defect states inside the SiN(x) films disappeared after H2 annealing. Flat band voltage shifts were observed in C-V curves, and their magnitudes decreased as the defect states inside the SiN(x) films decreased.

Fabrication of Epitaxial Silicon Thin Films for Solar Cells by Low-Temperature Reactive Thermal Chemical Vapor Deposition Technique

Low temperature reactive thermal chemical vapor deposition (RT-CVD) with a mixture of SiH4 and F2 gases has been developed to obtain silicon films with a relatively thick epitaxial layer for solar cell applications. It was found that an epitaxial layer with good crystallinity and a “2×1 structure” can be grown at approximately 400 °C up to a thickness of 3.0 µm and that the epitaxial growth shows a sudden breakdown at 3.2 µm to result in an amorphous phase. The growth mechanism, which determines the crystallinity for thicker layers, is discussed on the basis of hydrogen content and lattice distortion.

Electrical Properties of Silicon-Rich Silicon Carbide Films Prepared by Using Catalytic Chemical Vapor Deposition

We studied electrical properties of the silicon rich silicon carbide (SRSC) films deposited by catalytic chemical vapor deposition (Cat-CVD) technique. A mixture of SiH4, CH4 and H2 gas was employed as the source gas in deposition process. Atomic composition of SRSC films and formation of Si QDs in SRSC films depended on control of CH4/SiH4 mixture ratios. The each different tunneling behavior was observed in current-voltage (I-V) curve of two samples prepared at different CH4/SiH4 mixture ratios. The PL spectra of two samples were also each different. These results were analyzed with relating formation of Si QDs in SRSC films.

Hydrogen plasma treatment for improving bulk passivation quality of c-Si solar cells

We have investigated the effects of radio frequency hydrogen plasma (H-plasma) treatment on bulk passivation qualities of cast poly-crystalline silicon (poly c-Si) wafers. When the hydrogen treatment was performed directly to poly c-Si wafers, the plasma damage was introduced and it was difficult to improve the minority carrier lifetime by optimizing the plasma condition. Hydrogenated amorphous silicon oxide (a-SiO x :H) films deposited by RF-PECVD using a mixture of SiH 4, H 2 and CO 2 were employed as the protection and the passivation layers. We found that the lifetime of poly c-Si substrates passivated by a RF-PECVD a-SiO x :H films with additional H-plasma treatment showed an improvement of the overall effective lifetime. Annealing up to 400 °C also enhances the further diffusion of hydrogen, and the effective lifetime of the samples with H-plasma treatment increased 20–30% compared to the samples without treatment. This result clearly indicated that the H-plasma treatment improves the bulk passivation quality of poly c-Si wafers.

Excimer Laser Annealing Effects of Silicon-rich Silicon Nitride Films Prepared by Using Catalytic Chemical Vapor Deposition

We studied excimer laser annealing effects on silicon-rich silicon nitride films containing silicon quantum dots to develop silicon based flexible Light emitting diodes. The silicon-rich silicon nitride films were deposited by catalytic chemical vapor deposition system using a mixture of SiH4, NH3 and H2 gas. The substrate temperatures in all deposition process were less than 200 ° to use polyethersulphone substrate. The changing crystallity and density of silicon quantum dots were analyzed by photoluminescence spectra. The change in the luminescence behavior with nucleation of silicon quantum dots was observed after excimer laser annealing.

Vertically aligned silicon microwire arrays of various lengths by repeated selective vapor-liquid-solid growth of n-type silicon/n-type silicon

Repeated vapor-liquid-solid (VLS) growth with Au and PH3–Si2H6 mixture gas as the growth catalyst and silicon source, respectively, was used to construct n-type silicon/n-type silicon wire arrays of various lengths. Silicon wires of various lengths within an array could be grown by employing second growth over the first VLS grown wire. Additionally, the junction at the interface between the first and the second wires were examined. Current-voltage measurements of the wires exhibited linear behavior with a resistance of 850 Ω, confirming nonelectrical barriers at the junction, while bending tests indicated that the mechanical properties of the wire did not change.

Low-temperature deposition of highly crystallized silicon films on Al-coated polyethylene napthalate by inductively coupled plasma CVD

We prepared highly crystallized silicon films on Al-coated polyethylene napthalate (PEN) substrates using inductively coupled plasma chemical vapor deposition (ICP-CVD) at low temperature with a mixture of SiH 4/H 2 as the source gas. The microstructure of the films was evaluated using Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The effects of deposition parameters on the crystallinity of silicon films on bare and Al-coated PEN were systematically investigated. Compared to the films deposited on bare PEN, an obvious phase transition from amorphous to crystalline occurred when decreasing the SiH 4 dilution ratio [ R = [SiH 4]/([SiH 4] + [H 2])] to 4% for the films on Al-coated substrates. With increasing the input power from 300 W to 400 W, the crystallinity of the films on bare and Al-coated PEN are both improved at a low temperature as low as 85 °C. The film on Al-coated PEN shows excellent crystallization with crystalline fraction of 82% and preferred orientation of (1 1 1). It has been found that the interaction between precursors and aluminum layers plays an important role and there should exist a different crystallization mechanism as compared to traditional annealing crystallization of amorphous Si/Al layer in the crystallization process of silicon films on Al-coated PEN at low temperature.

Columnar growth of crystalline silicon films on aluminium-coated glass by inductively coupled plasma CVD at room temperature

Silicon films were grown on aluminium-coated glass by inductively coupled plasma CVD at room temperature using a mixture of SiH4 and H2 as the source gas. The microstructure of the films was evaluated using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. It was found that the films are composed of columnar grains and their surfaces show a random and uniform distribution of silicon nanocones. Such a microstructure is highly advantageous to the application of the films in solar cells and electron emission devices. Field electron emission measurement of the films demonstrated that the threshold field strength is as low as ∼9.8 V/μm and the electron emission characteristic is reproducible. In addition, a mechanism is suggested for the columnar growth of crystalline silicon films on aluminium-coated glass at room temperature.

Effect of Silane Flow Rate on Structure and Corrosion Resistance of Ti–Si—N Thin Films Deposited by a Hybrid Cathodic Arc and Chemical Vapour Process

Ti–Si–N thin films with different silicon contents are deposited by a cathodic arc technique in an Ar+N2 +SiH4 mixture atmosphere. With the increase of silane Bow rate, the content of silicon in the Ti–Si–N films varies from 2.0 at. % to 12.2 at. %. Meanwhile, the cross-sectional morphology of these films changes from an apparent columnar microstructure to a dense fine-grained structure. The x-ray diffractometer (XRD) and x-ray photoelectron spectroscopy (XPS) results show that the Ti–Si–N film consists of TiN crystallites and SiNx amorphous phase. The corrosion resistance is improved with the increase of silane Bow rate. Growth defects in the films produced play a key role in the corrosion process, especially for the local corrosion. The porosity of the films decreases from 0.13% to 0.00032% by introducing silane at the Bow rate of 14sccm.

Formation of nanocrystals embedded in a silicon nitride film at a low temperature (⩽200 °C)

Silicon-rich silicon nitride films with embedded silicon nanocrystals (Si NCs) were fabricated successfully on plastic substrates at a low temperature by catalytic chemical vapor deposition. A mixture of SiH 4 , NH 3 and H 2 was used as a source gas. Formation of the silicon nanocrystals was analyzed by photoluminescence spectra and was confirmed by transmission electron microscopy. The formation of Si NCs required an H 2 /SiH 4 mixture ratio that was higher than four.

The Influence of the Substrate on the Mechanical Properties of Si-Doped DLC Thin Films

In this work, Si-doped DLC films were deposited on stainless steel (316SS) and polycarbonate (PC) substrates by RF-PACVD in gas mixtures of SiH4+CH4, with 2, 5 and 10 vol.% SiH4. The increase of the Si content in the films led to a progressive drop in the hardness from 30 GPa down to 23 GPa whereas the elastic modulus increased from 124 GPa up to 146 GPa, as measured in the SS coated substrates. In the case of coated PC samples pop-in was observed in the loading curve which was interpreted by finite element simulation and nanoscratching techniques.

Secondary ion species containing nitrogen atoms from plasma-enhanced chemical vapor deposited silicon oxide films on silicon

Secondary ion species from plasma-enhanced chemical vapor deposited (PECVD) SiO 2 films have been investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Comparative studies of PECVD SiO 2 films prepared using a mixture of SiH 4/N 2O reaction gas at 400 °C with thermally oxidized SiO 2 films grown at 900 °C were carried out in the mid-range mass spectra from 95 to 165 amu. Small amounts of ion species containing nitrogen atoms, including Si 2O 2N +, Si 3O 2N +and Si 3O 3N +, were detected in the SiO 2 bulk from the PECVD SiO 2 films. Furthermore, large amounts of Si 3O 2N + and Si 2O 3N − were found at the interface between silicon and the SiO 2 films. Depth analysis showed that the intensity peak shapes of these ion species containing nitrogen atoms at the interface were closely coincident with those of Si 3O 3 + corrected by subtracting the influence of the SiO 2 matrix. The variation in the spectra of these ion species clearly indicates that two types of structures of oxynitride exist for the PECVD SiO 2 films in the SiO 2 bulk films and at the interface. These are likely produced by the reaction of reactive gas with SiO 2 and silicon surfaces where dangling bonds of silicon may exist in the different form.

P-μc-Si1−xGex:H thin film by VHF-PECVD

In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium (p-μc-Si1−xGex:H) was deposited by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH4 and GeF4 mixtures. The effect of GeF4 concentration on films’ composition, structure and electrical properties was studied. The results show that with the increase of GeF4 concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si1−xGex:H material with high conductivity, low activation energy (σ=1.68 S/cm, E g= 0.047 eV), high crystalline volume fraction (60%) and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail.

Diamond-like carbon films deposited on polycarbonates by plasma-enhanced chemical vapor deposition

Diamond-like carbon films were coated on optical polycarbonate using plasma-enhanced chemical vapor deposition. A mixture of SiH 4 and CH 4/H 2 gases was utilized to reduce the internal compressive stress of the deposited films. The structure of the DLC films was characterized as a function of film thickness using Raman spectroscopy. The dependence of G peak positions and the intensity ratio of I D/I G on the DLC film thicknesses was analyzed in detail. Other studies involving atomic force microscopy, ultraviolet visible spectrometry, and three adhesion tests were conducted. Good transparency in the visible region, and good adhesion between diamond-like carbon films and polycarbonate were demonstrated. One-time recordings before and after a DLC film was coated on compact rewritable disc substrates were analyzed as a case study. The results reveal that the diamond-like carbon film overcoating the optical polycarbonates effectively protects the storage media.

Optical and structural properties of polycrystalline 3C-SiC films

In this letter, polycrystalline 3C-SiC (111) films were deposited by plasma enhanced chemical vapor deposition system at a temperature of 670°C using a gas mixture of SiH4∕CH4∕H2∕(CF4). The optical properties of deposited films with different feed gases and different structures were investigated. In these studies, a broad photoluminescence band was observed for films with lower crystallinity and the radiative transitions between the conduction and valance band tails were suggested as the origin of the observed peak. The band gap of these polycrystalline SiC films was estimated at around 2.10eV.

Fabrication of nanocrystalline silicon carbide thin film by helicon wave plasma enhanced chemical vapour deposition

Nanocrystalline cubic silicon carbide thin films have been fabricated by helicon wave plasma enhanced chemical vapour deposition on Si substrates using the mixture of SiH 4, CH 4, and H 2 at a low substrate temperature of 300 °C. The infrared absorption spectroscopy analyses and microstructural characteristics of the samples deposited at various magnetic fields indicate that the high plasma intensity in helicon wave mode is a key factor to the success of growing nanocrystalline silicon carbide thin films at a relative low substrate temperature. Transmission electron microscopy measurements reveal that the films consist of silicon carbide nanoparticles with an average grain size of several nanometers, and the light emission measurements show a strong blue photoluminescence at room temperature, which is considered to be caused by the quantum confine effect of small size silicon carbide nanoparticles.

Electroless Deposition of Au Nanocrystals on Si(111) Surfaces as Catalysts for Epitaxial Growth of Si Nanowires

Au nanocrystals were prepared by reacting solutions containing NaAuCl 4 2H 2 0 with hydrogen-terminated silicon (111) surfaces. The nanocrystals catalyze the subsequent growth of silicon nanowires by chemical vapor deposition using a mixture of SiH 4 and HCl in a H 2 ambient. Depositing the metal nanocrystals from nonaqueous solutions, such as ethanol, minimizes the oxidation of Si that can occur in an aqueous solution and allows epitaxially aligned growth of the nanowires. The Au nanocrystals preferentially deposit onto hydrogen-terminated Si( 111) compared to silicon dioxide. This selective deposition allows positioning of nanocrystals on patterns formed using either conventional lithography or nanoimprint lithography.

Abnormal Crystallization of Silicon Thin Films Deposited byICP-CVD

Silicon thin films are deposited by inductively coupled plasmachemical vapour deposition (ICP-CVD) at a low temperature of350°C using a mixture of SiH4 and H2. Thestructures of the films are characterized by x-ray diffraction andRaman spectra. Under the optimum experimental conditions, we observethat the crystallinity of Si films becomes more excellent and thepreferred orientation changes from (111) to (220) with the decreasingdilution of SiH4 in H2. Such an abnormalcrystallization is tentatively interpreted in term of the high density,low electron temperature and spatial confinement of the plasma in theprocess of ICP-CVD.

X-ray photoelectron spectroscopy and structural analysis of amorphous SiOxNy films deposited at low temperatures

We establish, using a tetrahedral model, the bonding properties of amorphous silicon oxynitride (a-SiOxNy) films deposited at low temperatures (LTs) by electron-cyclotron resonance chemical-vapor deposition (ECRCVD) on several substrates and under various conditions of gas flows and total gas pressure in a dilute mixture of SiH4+N2 in Ar. The atomic percentage of each tetrahedral unit incorporated in the film network is calculated from the deconvolution of the high-resolution x-ray photoelectron spectroscopy (XPS) spectra in the Si 2p3∕2 region and corroborated by the results obtained from both survey scans and the high-resolution XPS spectra in the N 1s region. The Si3N4 phase is the most important one and the only bonding unit which is incorporated in all our LT ECRCVD SiOxNy films. The incorporation of all the other component tetrahedrons depends strongly on growth conditions. The threshold values of the N∕Si atomic ratio for which intrinsic defects, such as Si–Si bonds, are not incorporated in the network depend on the O∕Si ratio incorporated in the films, mainly due to the competition between oxygen and nitrogen atoms in their reaction with silicon dangling bonds. The effect of the total gas pressure on the atomic percentages of the oxidation states present in the LT ECRCVD SiOxNy films is qualitatively similar to the effect of the ion bombarding energy or the plasma density. O–N bonds are present only in samples having high amount of oxygen and nitrogen in their networks. For these films, our results show unambiguously the presence of the N–Si2O tetrahedron and suggest that N–Si3−νOν tetrahedrons with ν⩾2 are not incorporated in their networks. A correlation is observed between the N–Si2O and the Si–O3(ON) tetrahedrons whose component peak is localized at (104.0±0.2)eV in the Si 2p3∕2 region of the XPS data, which suggests that both bonding units coexist in these films as some sort of complex bonding configuration.