Abstract
ABSTRACT In the Siemens method, high-purity Si is produced by reducing SiHCl3 source gas with H2 ambient under atmospheric pressure. Since the pyrolysis of SiHCl3, which produces SiCl4 as a byproduct, occurs dominantly in the practical Siemens process, the Si yield is low (~30%). In the present study, we generated hydrogen radicals (H-radicals) at pressures greater than 1 atm using tungsten filaments and transported the H-radicals into a reactor. On the basis of the absorbance at 600 nm of WO3-glass exposed to H-radicals in the reactor, we observed that H-radicals with a density of ~1.1 × 1012 cm−3 were transported approximately 30 cm under 1 atm. When SiCl4 was supplied as a source into the reactor containing H-radicals and allowed to react at 850°C or 900°C, Si was produced more efficiently than in reactions conducted under H2 ambient. Because the H-radicals can effectively reduce SiCl4, which is a byproduct in the Siemens method, their use is expected to increase the Si yield for this method.
Highlights
Si is regarded as strategic and important material because it is a necessary component of computers, motor vehicles, and various household appliances
To improve the Si yield of the Siemens method, we have focused on hydrogen radicals (H-radicals) as a reducing agent [5,6]
The H-radicals should be generated at a pressure greater than 1 atm (~101 kPa) and trans ported into the 1 atm reaction chamber, because the conventional Siemens method is operated under ~1 atm to obtain enough Si production rate
Summary
Si is regarded as strategic and important material because it is a necessary component of computers, motor vehicles, and various household appliances. In the Siemens method, high-purity trichlorosilane (SiHCl3) and H2 gas are introduced into a bell jar; the SiHCl3 is reduced by H2 into Si on heated Si rods at approximately 1000–1200°C at 1 atm (eq 1): SiHCl3ðgÞþH2ðgÞ ! For H-radicals to be used in the Siemens method, they should be remotely supplied into the bell jar (reaction chamber) to prevent con taminants from the source gas or synthesized Si from affecting the H-radical generation process. The H-radicals should be generated at a pressure greater than 1 atm (~101 kPa) and trans ported into the 1 atm reaction chamber, because the conventional Siemens method is operated under ~1 atm to obtain enough Si production rate. We generated H-radicals at pressures greater than 1 atm with the filament method and transported them into a 1 atm chamber. In addi tion, the effect of H-radicals on the reduction of SiCl4 at 1 atm was investigated to enable the future applica tion of H-radicals in the Siemens method
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