High Temperature Chlorosilane Corrosion of AISI 316L

Abstract

Chlorosilanes are used at high temperatures throughout the world's semiconductor industries primarily as a way to refine and deposit silicon and silicon containing materials. They are most prevalent in the manufacture of solar grade polycrystalline silicon; an industry that has historically used high cost alloys to effectively handle corrosive chlorosilane species. This study focused on understanding the corrosion behaviors of AISI 316L stainless steel, a low cost alloy, in chlorosilane environments at a variety of industrially-relevant times (0-200 hours), temperatures (500-700 • C), and hydrogen chloride (HCl) mole fractions (0.0-0.06). It was observed that AISI 316L can form either predominately metal chloride or metal silicide corrosion products depending on the mole fraction of HCl. Increasing temperatures tend to favor metal silicide formation, a trend predicted by thermodynamically generated predominance diagrams. Additionally, metal silicide surface layer growth appears to be diffusion controlled with an apparent parabolic rate at long times and high temperatures. There is also evidence for reaction-limited iron silicide formation at lower temperatures. Improved understanding of metals in high-temperature chlorosilane environments will help guide materials selection processes, and ultimately facilitate cost-competitive deployment of silicon-based photovoltaic systems. Chlorosilane species are used throughout the semiconductor, polycrystalline silicon, and fumed silica industries, primarily as a way to refine, deposit, and produce silicon and silicon containing materials. 1-4A typical chlorosilane gas stream usually contains some mixture of silicon tetrachloride (SiCl 4 , STC), trichlorosilane (HSiCl 3 , TCS), dichlorosilane (H 2 SiCl 2 , DCS), silane (SiH 4 ), hydrogen chloride (HCl), and hydrogen (H 2 ). The presence of both silicon-and chlorinecontaining species creates a unique corrosion environment for the metallic materials tasked with handling chlorosilane gas streams due to the propensity of many metals to form both metal-chlorides and metal-silicides.Metal-silicide and metal-chloride formation has been studied extensively for other applications. For example, metal chlorides have been studied due to the presence of chlorine in many industrial processes and metal silicides have been studied due to their use in electronics. It is generally considered that chloride formation is more problematic than silicide formation in industrial applications. This is because metal chlorides have high vapor pressures (at elevated temperatures) and can reactively evaporate 5 while metal silicides are potentially protective by forming dense, well-adhered surface layers. Consequently, for chlorosilane service, many industrial plants use alloys that resist chloride attack; however, the implementation of expensive corrosion resistant alloys comes at great cost. This is especially true in the polysilicon industry, where economic silicon refinement requires many large reactors and other process vessels. Because of process...

High-Temperature (550–700°C) Chlorosilane Interactions with Iron

“…The corrosion testing system (diagram shown previously 19 ) used for these experiments created a hydrogen/STC environment by bubbling an adjustable amount of hydrogen gas into the bottom of a bottle of liquid STC. As the hydrogen bubbles rose through the STC, they become fully saturated with STC making the head space a consistent mixture of hydrogen gas and STC vapor.…”

“…The authors have described the methods for exposing samples to a STC environment previously, 19 but for clarity, they will briefly be described here. The corrosion testing system (diagram shown previously 19 ) used for these experiments created a hydrogen/STC environment by bubbling an adjustable amount of hydrogen gas into the bottom of a bottle of liquid STC. As the hydrogen bubbles rose through the STC, they become fully saturated with STC making the head space a consistent mixture of hydrogen gas and STC vapor.…”

“…Additionally, the authors have done some work in the field of chlorosilane corrosion of 316L stainless steel. [19][20][21] Again, this work was largely studying the implications of using 316L in chlorosilane environments rather than investigating the specific mechanisms of corrosion. To the best knowledge of the authors, there are no published studies detailing the corrosion mechanisms of iron in chlorosilane environments representative of industrial processes.…”

Methods of trichlorosilane synthesis for polycrystalline silicon production. Part 1: Direct synthesis

“…Currently there are studies of the corrosion resistance under trichlorosilane synthesis conditions for a 4 Pat. WO 2008WO /088465, 2008 cheaper steel AISI316L containing 10.0-13.0% Ni; 2.0-2.5% Mo; 16.5-18.5% Cr; 2.0 % Mn; 0.045% P;1.0% Si; 0.030 % С [63].…”

The Effect of Zirconium and Yttrium Oxide on the Microstructure and Mechanical Properties of Ti-Si-Zr Based Composites

“…[12] The M x Si y -type compounds change the structure and phase composition of the composite through improved grain refinements, reaction efficiency, density, and porosity. [13,14] For example, elemental Zirconium (Zr) in the Ti-Si matrix forms a Ti-Si-Zr solidsolution, which improves the creep resistance, hardness, and yield strength of the composite. [7,15,16] Qiao et al [17] observe that Zr has little effect on the α and β phases of the Ti-Si system and maintains good high-temperature stability.…”