Trichlorosilane Gas Research Articles

Electrochemical production of silicon

AbstractSilicon solar cells are crucial devices for generating renewable energy to promote the energy and environmental fields. Presently, high-purity silicon, which is employed in solar cells, is manufactured commercially via the Siemens process. This process is based on hydrogen reduction and/or the thermal decomposition of trichlorosilane gas. The electrochemical process of producing silicon has attracted enormous attention as an alternative to the existing Siemens process. Thus, this article reviews different scientific investigations of the electrochemical production of silicon by classifying them based on the employed principles (electrorefining, electrowinning, and solid-state reduction) and electrolytes (molten oxides, fluorides, chlorides, fluorides–chlorides, ionic liquids [ILs], and organic solvents). The features of the electrolytic production of silicon in each electrolyte, as well as the prospects, are discussed.

Quartz crystal microbalance for real-time monitoring chlorosilane gas transport in slim vertical cold wall chemical vapor deposition reactor

Chlorosilane gas transport in ambient hydrogen in a slim vertical cold wall chemical vapor deposition reactor was real-time monitored using a quartz crystal microbalance (QCM) using its behaviour responding to the properties of the gas mixture. The QCM frequency quickly decreased by introducing the trichlorosilane gas, while it slowly decreased by the dichlorosilane gas. The QCM frequency behavior was explained by the gas flow condition, such as the plug flow and recirculating flow, in the reactor. The relationship was consistent with the gas flow calculations, because the heavy and light gases could directly flow downward and recirculate, respectively, in the chamber due to natural convection. The information obtained from the QCM frequency behavior is expected to be utilized for the real-time gas monitoring and for the process design.

Real time evaluation of silicon epitaxial growth process by exhaust gas measurement using quartz crystal microbalance

A silicon epitaxial growth process in a trichlorosilane-hydrogen system was evaluated using a quartz crystal microbalance (QCM) placed at the exhaust of a chemical vapor deposition reactor designed for the Minimal Fab. The QCM showed two types of the frequency decrease behaviors, that is, i) a quick shift due to the gas property change caused by the trichlorosilane gas introduction into the ambient hydrogen and ii) the continuous and gradual decrease due to the byproduct deposition on the QCM surface during the silicon epitaxial growth. Because both i) and ii) showed a relationship with the silicon epitaxial growth rate, the in-situ information obtained by the QCM was expected for the real time monitoring of the film deposition process.

Advantages of a slim vertical gas channel at high SiHCl3 concentrations for atmospheric pressure silicon epitaxial growth

Effective process conditions to utilize a slim vertical silicon chemical vapour deposition reactor were studied. Based on a numerical analysis taking into account the gas flow, heat and species transport, particularly over a wide range of the trichlorosilane gas concentrations from 1% to 40% in ambient hydrogen, a heavy and cold gas was shown to quickly go downward to the hot wafer surface through the slim vertical gas channel. The gas phase near the wafer was sufficiently cooled to produce a cold wall thermal condition which enabled the trichlorosilane gas consumption only at the wafer surface, even in a non-axisymmetric and non-steady condition. The slow wafer rotation, less than 30 rpm, had a considerable effect, such as that increasing the gas phase temperature gradient for suppressing the gas phase reaction.

Transport phenomena in a slim vertical atmospheric pressure chemical vapor deposition reactor utilizing natural convection

The gas flow, heat and species transport in a slim vertical silicon chemical vapor deposition reactor for Minimal Fab were evaluated by a numerical analysis. The influences of the inlet gas flow condition on the gas flow direction and the gas phase temperature in the reactor were studied. When the gas flow rate was minimized, natural convection transports the precursor of trichlorosilane gas to the wafer surface. Because the wafer rotation, even very slow at 4rpm, adjusted the gas flow to shrink the hot region height above the wafer, the gas phase reaction was moderated for preparing the specular surface of the epitaxial film.

Increase in silicon film deposition rate in a SiHCl3-SiHx-H2 system

The silicon film deposition rate at 850°C using trichlorosilane gas was increased by adding SiHx gas which was in situ produced by the thermal decomposition of monomethylsilane gas in ambient hydrogen. With the increasing monomethylsilane gas concentration, the amounts of the chlorosilanes in the gas phase and the by-product deposited at the exhaust decreased. The influence of CHx on the deposition rate was negligible, because the carbon concentration contained in the silicon film obtained in this study was comparable to that formed only by the trichlorosilane gas.

In Situ Measurement for Evaluating Temperature Change Related to Silicon Film Formation in a SiHCl3-H2 System

The temperature change related to silicon film formation in a trichlorosilane-hydrogen system was evaluated by an in situ monitoring method using the langasite crystal microbalance (LCM). First, the time constants for the LCM frequency change due to the surface and gas phase temperature change were determined to be less than two hundred seconds. The continuous LCM frequency decrease appearing two hundred seconds after changing the trichlorosilane gas concentration was assigned to the weight increase by the film formation in a steady state. Based on an evaluation of the difference in the LCM frequency between those with and without the heat change related to the film formation, the surface temperature decrease caused by slightly changing the trichlorosilane concentration was comparable to one degree.

In‐situ observation of chemical vapor deposition using SiHCl3 and BCl3 gases

AbstractThe lowest temperature for initiating the film deposition was evaluated by in situ monitoring using a highly sensitive langasite crystal microbalance (LCM) in order to produce a thin boron doped silicon film using trichlorosilane gas and boron trichloride gas at low temperatures. The thin films of silicon, boron and boron‐doped silicon were individually formed from the trichlorosilane gas, boron trichloride gas and their gas mixture, respectively, on the LCM. The silicon film deposition occurred between 570 and 600 °C, while the boron film deposition occurred between 470 and 530 °C. The film deposition from both gases occurred at temperatures higher than 530 °C. Based on secondary ion mass spectrometry measurements, the boron‐doped silicon film was determined to be formed on the silicon substrate at 570 °C. Thus, the LCM could be useful for developing a thin film formation process including that for doping. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

By-Product Formation in a Trichlorosilane-Hydrogen System for Silicon Film Deposition

The process of by-product formation during silicon film deposition using trichlorosilane gas was studied by two types of the in situ measurement techniques, such as the langasite crystal microbalance (LCM) and the quadrupole mass spectra (QMS) analyzer, installed at the exhaust of the chemical vapor deposition (CVD) reactor. With the increasing hydrogen gas concentration, the QMS showed that the partial pressure related to SiCl2 decreased. Simultaneously, the deposition on the LCM surface decreased. Because SiCl2 gradually produces the burnable by-product of (SiCl2)n, an oily silane, at the exhaust, the CVD parameters effective for suppressing the SiCl2 formation were evaluated.

Low temperature amorphous silicon carbide thin film formation process on aluminum surface using monomethylsilane gas and trichlorosilane gas

The low-temperature chemical vapor deposition process of silicon carbide (SiC) on an aluminum surface was developed. In order to prepare the reactive substrate surface, a silicon interlayer containing silicon dimers at its surface was formed using trichlorosilane gas at 600°C. Next, the SiC thin film was formed at room temperature using monomethylsilane gas. Silicon, carbon and silicon-carbon bond in the obtained film were detected by various evaluations. The SiC film was amorphous and about 5-nm thick.

<i>In-Situ</i> Monitoring of Chemical Vapor Deposition from Trichlorosilane Gas and Monomethylsilane Gas Using Langasite Crystal Microbalance

Using the langasite crystal microbalance (LCM), the trends in film thickness produced by means of the chemical vapor deposition using trichlorosilane gas, monomethylsilane gas and their mixed gas were observed at 600?C and evaluated by comparison with the information from a transmission electron microscope (TEM). The crystalline silicon film thickness from trichlorosilane gas was comparable to that of an amorphous silicon carbide film from monomethylsilane gas. The film obtained from the gas mixture was amorphous and was the thinnest in this study. Because the thickness trend obtained by the LCM agreed with that by the TEM, the LCM is shown to be a convenient evaluation tool for the behavior of various film deposition.

Low Temperature SiC Film Deposition Using Trichlorosilane Gas and Monomethylsilane Gas

In order to produce silicon carbide thin film through the process entirely at low temperatures, silicon carbide chemical vapor deposition on a silicon wafer surface was performed using trichlorosilane gas and monomethylsilane gas. First, the silicon thin film was formed using trichlorosilane gas at 800 degrees C and was cooled to room temperature in ambient hydrogen, in order to produce hydrogen-terminated silicon surface. Next, monomethylsilane gas was introduced at room temperature to produce silicon carbide thin film. The mirror-like appearance of the film obtained by this process was maintained after the exposure to hydrogen chloride gas at 800 degrees C. Furthermore, very thin Si-C layer was detected at the surface by means of the time-of-flight secondary ion mass spectrometry. Thus, the silicon carbide thin film was concluded to be formed through the process at temperatures below 800 degrees C.

Silicon epitaxial growth process using trichlorosilane gas in a single-wafer high-speed substrate rotation reactor

A silicon epitaxial growth process in a trichlorosilane–hydrogen system using a single-wafer high-speed substrate rotation reactor was studied by means of experiments and numerical calculations taking into account the transport phenomena and surface chemical reactions. Hydrogen chloride gas produced at the substrate surface is effectively replaced with the source gases of trichlorosilane and hydrogen, due to the effective mass transport provided by high-speed substrate rotation. Because the intermediate species produced due to chemisorption of trichlorosilane fully occupies the silicon surface, the rate of its decomposition by hydrogen gas governs the entire silicon epitaxial growth rate. Thus, the epitaxial growth rate in this reactor simply depends on the hydrogen gas concentration at the silicon substrate surface.