SiO2 Deposition Rate Research Articles

Silica coating of Fe-6.5 wt%Si particles using fluidized bed CVD: Effect of precursor concentration on core–shell structure

In this study, Fe–Si@SiO2 core–shell particles were synthesized by a fluidized bed chemical vapor deposition process at various gaseous C8H20O4Si precursor concentrations (2.0–5.5 vol%). The substrate temperature and deposition times for the study were 920 K and 30 min, respectively. The influence of gaseous C8H20O4Si precursor concentration on the microstructures and performances of the Fe–Si@SiO2 core–shell particles was investigated. X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to confirm the reaction mechanism of C8H20O4Si on the Fe-6.5 wt%Si substrate particles. The evolution process from the Fe-6.5 wt%Si to the Fe–Si@SiO2 core–shell structure that the greats quantity were in condensation reactions among C8H20O4Si precursor, Si(OC2H5)x(OH)4−x (x = 0–3) intermediate products and Fe-6.5 wt%Si substrate particles. The gaseous C8H20O4Si precursor concentration changes the surface morphology of the particles and increases the SiO2 deposition rate. Sub-micro scale SiO2 deposits, porous and partially covered SiO2 coatings, complete SiO2 coatings, and microscale SiO2 clusters were dominant at low, intermediate, and high concentrations of gaseous C8H20O4Si precursor. Upon increasing the gaseous C8H20O4Si precursor concentration from 2.0 to 4.0 vol%, the SiO2 deposition rate demonstrated a linear increase. A gaseous C8H20O4Si precursor concentration of 3.0 vol% was necessary to obtain a complete Fe–Si@SiO2 core–shell structure. The magnetic moment per unit weight of the complete Fe–Si@SiO2 core–shell particles were slightly lower than that of Fe-6.5 wt%Si substrate particles, while the resistivity values increased by three orders of magnitude.

Formation and optimization of deposition surface shape during fused silica glass synthesis by chemical vapor deposition

AbstractThis paper investigates the effects of deposition surface shape on temperature distribution of fused silica glass by SiCl4 chemical vapor deposition and performs the optimization of deposition surface shape to obtain the glass with a small temperature gradient. The computational model is first developed to describe the complicated physical and chemical phenomenon in the system. Numerical simulations are then performed to evaluate the effects of SiCl4 injection position on flame characteristics and SiO2 deposition rate. It is found that the SiO2 deposition rates with the unimodal, uniform, and bimodal distributions are obtained when SiCl4 is injected from the central, secondary layer and fourth layer nozzles, respectively. The deposition surface shape is mainly determined by the gas temperature gradient and particle number density near the deposition surface. Thereafter, the temperature distributions in synthetic silica glass are presented for the cases with convex, flat, and concave deposition surface shapes. Large temperature gradients exist at the side of glass if the convex and concave surfaces are formed, although a high temperature uniformity is obtained in the center of glass for the convex deposition surface. The optimal surface shape that has a very small temperature gradient in glass is obtained by the optimization of deposition surface depth.

Study of the Influence of Temperature on the Deposition of SiO<sub>2</sub> Films from Reaction of Silicone Oil Vapor and Ozone Gas

This work reports the influence of deposition temperature on the deposition of SiO2 films on silicon substrate by using chemical reaction of silicone oil vapor andozone gas at low temperature. An organic solution as a catalyst at atmospheric pressure has been used to enhance the deposition rate of SiO2. The deposition rate of SiO2 films was found to vary with the variation of the concentration of the catalyst and deposition temperature (160°C ~ 260°C). The deposited SiO2 films were confirmed by Fourier transform infrared (FTIR) spectroscopy. The thickness and refractive index of the as-deposited films were measured by the laser ellipsometry. FT-IR spectra of the as-deposited films were very much similar to those of SiO2 films found in literature. The deposition temperature was found to influence the deposition rate of SiO2 strongly. The maximum deposition rate was found to 17.2 nm per minute for the case of 220°C. The deposition temperature also influenced the refractive index of the films. Experimental results showed that the deposition temperature could be a major parameter for the enhancement of the deposition rate.

Modeling chemical vapor deposition of silicon dioxide in microreactors at atmospheric pressure

We developed a multiphysics mathematical model for simulation of silicon dioxide Chemical Vapor Deposition (CVD) from tetraethyl orthosilicate (TEOS) and oxygen mixture in a microreactor at atmospheric pressure. Microfluidics is a promising technology with numerous applications in chemical synthesis due to its high heat and mass transfer efficiency and well-controlled flow parameters. Experimental studies of CVD microreactor technology are slow and expensive. Analytical solution of the governing equations is impossible due to the complexity of intertwined non-linear physical and chemical processes. Computer simulation is the most effective tool for design and optimization of microreactors. Our computational fluid dynamics model employs mass, momentum and energy balance equations for a laminar transient flow of a chemically reacting gas mixture at low Reynolds number. Simulation results show the influence of microreactor configuration and process parameters on SiO2 deposition rate and uniformity. We simulated three microreactors with the central channel diameter of 5, 10, 20 micrometers, varying gas flow rate in the range of 5-100 microliters per hour and temperature in the range of 300-800 °C. For each microchannel diameter we found an optimal set of process parameters providing the best quality of deposited material. The model will be used for optimization of the microreactor configuration and technological parameters to facilitate the experimental stage of this research.

Effect of Series Capacitance and Accumulated Charge on a Substrate in a Deposition Process with an Atmospheric-Pressure Plasma Jet

In order to investigate the effect of accumulated charge on a substrate surface in the deposition of a SiO2 film with an atmospheric-pressure plasma jet, we have measured the discharge current flowing into a copper substrate, which was placed 20 mm from the exit of the plasma jet and connected to a variable capacitor in series. We found that the discharge current decreased markedly when the capacitance of the substrate was below 100 pF, and the deposition rate of SiO2 traced the variation of the capacitance. To analyze the behavior of the plasma jet, we considered an equivalent circuit of our system and verified the validity of our supposition that the accumulated charge restricts the deposition rate. Thereby, we found that the discharge current and deposition rate were determined by the capacitance of both the glass tube wall and the substrate.

Ge O 2 -doped SiO2 sputtered thin films: Microstructure, stoichiometry, and optical properties

Radio frequency sputtering is a reliable and low-cost technique for the deposition of oxide thin films. Here we report on the nonreactive preparation of SiO2 and SiO2–GeO2 films, which can be of interest in optics and optoelectronics. The deposition rate of SiO2–GeO2 is roughly three times higher than that of SiO2. Secondary ion mass spectroscopy shows SiO nonstoichiometry in SiO2 films, and the formation of Ge or Ge-based defects in SiO2–GeO2 samples. The best fits of the ellipsometric spectra confirm the nonstoichiometry of SiO2 films, showing that SiO fraction (and the refractive index, n) tends to decrease by increasing the deposition time.

Electron beam ablation of materials

The channelspark, a low accelerating voltage, high current electron beam accelerator, has been used for ablation of materials applied to thin film deposition. The channelspark operates at accelerating voltages of 10 to 20 kV with ∼1500 A beam currents. The electron beam ionizes a low-pressure gas fill (10–20 mTorr Ar or N2) to compensate its own space charge, allowing ion focused transport. Ablation of TiN, Si, and fused silica has been studied through several plasma diagnostics. In addition, thin films of SiO2 have been deposited and analyzed. Strong optical emission from ionized species, persisting for several microseconds, was observed in the electron beam ablated plumes. Free electron temperatures were inferred from relative emission intensities to be between 1.1 and 1.2 eV. Dye-laser-resonance-absorption photography showed Si atom plume expansion velocities from 0.38 to 1.4 cm/μs for several pressures of Ar or N2 background gas. A complex, multilobed plume structure was also observed, yielding strong indications that an electron beam instability is occurring, which is dependent upon the conductivity of the target. Nonresonant interferometry yielded line-averaged electron densities from 1.6 to 3.7×1023 m−3 near the target surface. Resonant UV interferometry performed on Si neutral atoms generated in the ablation plumes of fused silica targets measured line integrated densities of up to 1.6×1016 cm−2, with the total number of ablated silicon neutrals calculated to be in the range 2.0×1015 to 5.0×1013. Electron beam deposited films of fused silica were microscopically rough, with a thickness variation of 7%. The average SiO2 deposition rate was found to be about 0.66 nm/shot. The electron beam-deposited fused silica films had accurately maintained stoichiometry. Ablated particulate had an average diameter near 60 nm, with a most probable diameter between 40 and 60 nm. For SiO2 targets, the mass of material ablated in the form of particulate made up only a few percent of the deposited film mass, the remainder being composed of atomized and ionized material.

Effect of a chemical modification on growth silicon dioxide films on gallium arsenide prepared by the liquid phase deposition method

This article presents a chemical modification process to grow silicon dioxide (SiO2) on a gallium arsenide (GaAs) substrate using liquid phase deposition (LPD) at extremely low temperature (∼40 °C). In this process, pretreatment of the wafer by ammonia solution with buffer kept at pH=11–12 enriches OH radical formation on the GaAs surface, enhancing SiO2 deposition, providing good film quality, and reliability. The LPD SiO2 deposition rate on GaAs substrate is up to 1303 Å/h. The refractive index of the LPD SiO2 film on GaAs substrate is about 1.423 with growth at 40 °C. When the LPD SiO2 film on GaAs substrate is used to fabricate a metal–oxide–semiconductor capacitor, the surface charge density (Qss/q) is about 3.7×1011 cm−2 and the leakage current is 43.3 pA at −5 V. A mechanism for the deposition of silicon dioxide on a GaAs substrate is proposed.

Improved formation of silicon dioxide films in liquid phase deposition

This work is to reveal the novel technique of liquid phase deposition silicon dioxide (SiO2) films which will increase the deposition rate and also improve the film quality. It is well known that deposition at a lower temperature without residual OH− on the substrate is difficult to achieve. Therefore, it is important to treat the substrate wafer before deposition. The substrate surface dipped into hydrofluoric acid (HF) is usually terminated with hydrogen (H) and has hydrides (Si–H) which react with water so that hydroxyls (Si–OH) can be obtained. No silicon dioxide can be grown on a clean Si substrate without native oxide. Therefore, a model is proposed to show that native oxide growth with chemical pretreatment of HF and ultrapure deionized water has rich hydroxyl (OH) molecules on surface in order to grow silicon dioxide. Another constant parameter, the growth rate of SiO2 is found to increase linearly with the time of reaction with ultrapure deionized water. At the same concentration of boric acid and hydrofluosilicic acid, the corresponding deposition rate of SiO2 is found to be about 70 Å/h larger than the films which are grown without reacting with chemical pretreatment of HF and ultrapure deionized water. In this study, the refractive index and deposition rate are found to be as high as 1.47 and 1400 Å/h, respectively. Good and reliable quality SiO2 film grown in this work was supported by various analytical techniques, such as Fourier transform infrared, Auger electron spectroscopy, refractive index measurement, etching rate measurement, and leakage current measurement.

Controllability of gap‐filling for intermetal SiO2 deposition by biased helicon plasma chemical vapor deposition

AbstractThe gap between patterned aluminum was filled with SiO2 formed by the reaction of SiH4‐O2 gas using helicon plasma and a biased substrate. The relationship between the SiO2 deposition rate and plasma source power was investigated.It was found that the SiO2 deposition rate was dependent on the rate of SiH4 supply and was independent of the plasma source power. The sputtering rate due to biasing the substrate decreased with increase of the plasma source power. It was found also that the sputtering rate at which void generation is suppressed could be controlled not only by the bias power but also by the plasma source power. Even when the plasma source power and bias power were set at a low level, a sufficient sputtering rate was obtained. The gap‐filling rate (the net deposition rate) was determined by the difference between the raw deposition rate determined by SiH4 supply and the sputtering rate and could be controlled by the plasma source power.

Adsorption and decomposition of diethyldiethoxysilane on silicon surfaces: New possibilities for SiO2 deposition

Diethyldiethoxysilane is an organosilicate that may offer new possibilities for SiO2 deposition. In this study, the adsorption and decomposition of diethyldiethoxysilane (DEDEOS) was examined on Si(100)2×1 and porous silicon surfaces using laser-induced thermal desorption (LITD), temperature-programmed desorption (TPD), Fourier-transform infrared (FTIR), and Auger electron spectroscopy techniques. The FTIR studies revealed that DEDEOS dissociatively adsorbs on porous silicon and deposits ethyl and ethoxy species. These species are observed to decompose via a β-hydride elimination mechanism at ∼700 K. In agreement with this mechanism, TPD studies on Si(100)2×1 observed ethylene (C2H4) at ∼700 K and H2 desorption at ∼800 K. Additionally, the controlled deposition of SiO2 was achieved on Si(100)2×1 using repetitive cycles of DEDEOS adsorption at 300 K followed by thermal annealing at 820 K for 300 s. After the rapid deposition of an oxygen coverage of θO∼2.4 ML, the oxygen deposition rate decreased and reached a constant deposition rate of ∼0.04 ML oxygen per cycle after ten cycles. The constant reactivity of the growing SiO2 film was attributed to dangling bond reactive sites resulting from β-hydride elimination of the ethyl groups (SiCH2CH3→SiH+CH2=CH2) and subsequent H2 desorption (2SiH→2Si+H2). DEDEOS was also utilized to grow SiO2 films under high-pressure chemical vapor deposition conditions. The rate of SiO2 deposition displayed Arrhenius behavior with an activation barrier of Eact=49±6 kcal/mol. This activation barrier is similar to activation barriers measured earlier for SiO2 growth using tetraethoxysilane (TEOS). The deposition rate of SiO2 by DEDEOS was approximately 60 times slower than the deposition rate by TEOS at 943 K and 0.5 Torr.

Infrared absorption spectroscopy for monitoring condensible gases in chemical vapor deposition applications

In situ infrared absorption spectroscopy is used to monitor the delivery of condensible gases in chemical vapor deposition (CVD) systems. A Fourier transform infrared (FTIR) spectrometer has been configured to enable simultaneous measurements of the concentrations of multiple gases which are critical to the performance of CVD processes. In the deposition of silicon dioxide (SiO2) films using tetraethylorthosilicate (TEOS) and ozone (O3), IR measurements of the concentration of gas-phase TEOS closely track the deposition rate of SiO2. In doped oxide deposition processes, the percentage of phosphorous in the film is predicted from infrared measurements of the concentration of the dopant precursor gas [trimethylphosphene (TMP)]. These capabilities provide improved control of the delivery of condensible gases in CVD systems without the use of test wafers, and they enable the detection of failures in the gas delivery system in real time.

Catalytic effect of phosphine on the deposition of phosphosilicate glass from tetraethoxysilane

The effect of phosphorous incorporation on the deposition rate of phosphosilicate glass from the reaction of PH3, O2, and tetraethoxysilane (TEOS) has been studied. The previously reported apparent catalytic effect of PH3 on the deposition rate of SiO2 has been reproduced in this study, but by utilizing a newly designed hot-walled low-pressure chemical vapor deposition (LPCVD) reactor, homo- and heterogeneous catalytic effects were separated. These results indicate that the source of the catalytic effect is purely homogeneous, possibly involving an oxidation product of PH3 reacting with TEOS. Results obtained in a cold-wall reactor suggest that PH3 and O2 serve to poison the surface decomposition reaction of TEOS to produce SiO2.

Time-of-Flight Measurement of Particles in SiO2 Sputtering

The decrease of the deposition rate of SiO2 sputtered films is investigated by using time-of-flight apparatus. It is found that the increase of signal intensity of H atoms corresponds to the decrease of the deposition rate of SiO2 films, which confirms the reports by Hosokawa that the absorbed H2O at the target surface is the most important factor affecting the decrease of the deposition rate of SiO2 films.

Laser-induced chemical vapor deposition of SiO2

We have demonstrated rapid (3000 Å/min) photochemical deposition of silicon dioxide from gas phase donor molecules. An ArF (193 nm) laser was used to excite and dissociate gas phase SiH4 and N2O molecules in contrast to earlier work with incoherent mercury lamps. We have achieved 20 times the deposition rate, limited the dissociation volume to a localized region, and minimized the direct impingement of UV photons on the substrate. Although the SiO2 deposition rate was insensitive to substrate temperature from 20 to 600 °C, film quality noticeably improved above 200 °C. Metal-oxide-semiconductor capacitors were fabricated and characterized in order to measure SiO2 electrical properties. Film composition was investigated using Auger and infrared spectroscopy techniques and showed that the SiO2 is stoichiometric and contains less than 5% nitrogen.

ｒｆスパッタリングによるＳｉＯ?S２?Tの付着速度と真空系の質

In spite of carefull regulation, the reproducibility of SiO2 deposition rate has been sometimes poor in an rf sputtering system. This paper describes systematic experiments on the relationship between the deposition rate and vacuum quality in some sputtering systems. Data of the deposition rate versus vacuum characteristic parameters such as ultimate prssure, argon flow rate during sputtering, leak rate of air or water vapour, and baking time of the sputtering chamber are given. In addition gas analysis made by quadrupole mass filter shows that the pressure of water vapour is commonly most responsible for the reproducibility of the deposition rate. Internal liquid nitrogen trap pumping selectively water has been proved to be effective to suppress the decrease of the deposition rate and to improve reproducibility.