Trichlorosilane Purification via Complexation Distillation
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Solution Overview
Problem
Current methods for purifying technical grade trichlorosilane and silicon tetrachloride to achieve electronic grade quality are inefficient, as they fail to adequately remove impurities such as boron, metallic, and phosphorus chlorides, limiting their use in semiconductor production and epitaxial layer growth due to high investment costs and impurity residue.
Innovation Solution
A three-step process involving complexation of boron and metallic impurities with diphenylthiocarbazone and triphenylchloromethane, followed by distillation to remove impurities and achieve electronic grade purity, utilizing a plant with specific temperature and reflux control to ensure effective impurity removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hyper distillation is used to purify TCS TG and TET TG, then impurity removal is achieved, but investment costs become very high due to high columns and high reflux ratios
Solution Approach 1:
The patent applies preliminary action by performing complexation reactions before distillation to convert impurities into separable forms. Diphenylthiocarbazone and triphenylchloromethane are added to complex with boron, phosphorus, and arsenic impurities, transforming them into compounds that can be more easily removed in subsequent distillation steps, thereby reducing the complexity of the distillation process while maintaining high purity levels
Solution Approach 2:
The patent uses complexing agents (diphenylthiocarbazone and triphenylchloromethane) as intermediaries to facilitate impurity removal. These intermediaries selectively bind to impurities like boron trichloride, phosphorus trichloride, and arsenic trichloride, forming complex compounds that have different volatility characteristics, enabling more efficient separation during distillation without requiring excessively high columns or reflux ratios
2Manufacturing precision
If wet nitrogen bubbles process is used, then purification is achieved, but purity grade does not exceed P-type value of 100 ohm-cm due to limited complexing capacity
Solution Approach 1:
The patent changes the chemical parameters of the complexing agents by using diphenylthiocarbazone and triphenylchloromethane instead of water. These organic complexing agents have significantly higher complexing capacity for metal impurities compared to water molecules. The patent optimizes parameters such as the molar ratio of complexing agents to impurities, temperature, and reaction time to maximize complexation efficiency, achieving purity grades well above P-type 100 ohm-cm
Solution Approach 2:
The patent employs a composite approach by using two different complexing agents (diphenylthiocarbazone and triphenylchloromethane) working together. Each agent has complementary complexing capabilities, and their combined use enhances the overall complexing capacity and selectivity for different impurities, achieving superior purification results compared to using a single agent or water-based systems
3Manufacturing precision
If complexation with electron rich big molecules is used, then purification is improved, but optimal electronic grade purity is not achieved for epitaxial reactor applications
Solution Approach 1:
The patent applies local quality by using different complexing agents for different impurity types. Diphenylthiocarbazone is particularly effective for boron compounds, while triphenylchloromethane targets phosphorus and arsenic impurities. This selective complexation approach ensures that each impurity type is addressed by the most effective agent, achieving the optimal purity level required for epitaxial reactor applications where even trace impurities can affect semiconductor quality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process significantly reduces boron and metallic impurities, achieving a high purity level suitable for semiconductor production and epitaxial layer growth, with improved stability and repeatability compared to previous methods.
Implementation Method 1
complexation of the boron impurities (trichloride BCl3) and other metallic impurities by addition of diphenylthiocarbazone and triphenylchloromethane, with the formation of complex macromolecules having high boiling point
Implementation Method 2
first column distillation of the complexation step products, wherein the complexed boron impurities, together with other metallic impurities are removed as bottoms
Data Source
AI summary
The present disclosure relates to processes and systems for purifying technical grade trichlorosilane and/or technical grade silicon tetrachloride into electronic grade trichlorosilane and/or electronic grade silicon tetrachloride.