Chlorosilane Purification via Aldehyde-Oxidation Distillation
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Solution Overview
Problem
Current methods for purifying chlorosilanes fail to effectively remove boron and phosphorous impurities, which remain in the final product and affect the electrical characteristics of polycrystalline silicon, due to the impurities' low boiling points and the need for high-temperature processes or complex handling of chemicals.
Innovation Solution
A method involving the reaction of chlorosilanes with oxygen in the presence of an aromatic aldehyde, such as benzaldehyde, to convert boron and phosphorous impurities into high-boiling compounds, which can then be easily separated through distillation, using a process that operates at moderate temperatures (0°C to 150°C) and with easily handled additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a general distillation process is used to purify chlorosilanes, then the purification process is simple and operates at moderate temperatures, but boron and phosphorous impurities with low boiling points cannot be effectively removed
Solution Approach 1:
The patent applies preliminary action by converting boron and phosphorous impurities into high-boiling compounds before the distillation process. This is achieved by introducing oxygen and an aromatic aldehyde into the raw chlorosilanes, which react with the impurities to form compounds with significantly higher boiling points. This preliminary conversion enables the subsequent simple distillation to effectively separate and remove the impurities, resolving the contradiction between process simplicity and purification effectiveness.
2Manufacturing precision
If high-temperature processes are used to remove boron and phosphorous impurities, then impurity removal efficiency is improved, but the process complexity and handling difficulty increase
Solution Approach 1:
The patent applies parameter changes by modifying the boiling point parameter of the impurities through chemical reaction rather than changing the temperature parameter of the process. By reacting boron and phosphorous impurities with oxygen and aromatic aldehyde to form high-boiling compounds, the impurities' boiling points are fundamentally altered. This enables effective separation at moderate temperatures, avoiding the need for complex high-temperature equipment and processes while maintaining high removal efficiency.
3Temperature
If conventional distillation is used, then the process operates at moderate temperatures, but boron and phosphorous compounds with low boiling points remain in the final product
Solution Approach 1:
The patent introduces oxygen and aromatic aldehyde as intermediary substances that mediate between the moderate temperature process and the effective removal of low-boiling impurities. These intermediaries react with boron and phosphorous impurities to form high-boiling compounds, creating a bridge that allows moderate temperature distillation to achieve the separation effectiveness normally requiring high temperatures. This intermediary mechanism resolves the contradiction between operating temperature and purification precision.
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
This method simultaneously and efficiently removes boron and phosphorous impurities from chlorosilanes, producing high-purity chlorosilanes without the need for high-temperature conditions or complex waste treatment, while using inexpensive and easily handled reagents.
Implementation Method 1
a step (A) of making chlorosilanes containing a boron impurity and a phosphorous impurity react with oxygen in the presence of an aromatic aldehyde to convert the boron impurity and the phosphorous impurity into compounds having a higher boiling point than chlorosilanes
Implementation Method 2
a step (B) of separating said compounds of boron and phosphorous from the chlorosilanes
Data Source
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AI summary
This method for purifying chlorosilanes includes: introducing oxygen (O2) into the chlorosilanes containing a boron impurity and a phosphorous impurity in the presence of an aromatic aldehyde; treating the chlorosilanes to convert the impurities into high boiling compounds at the same time; and subjecting the chlorosilanes after having been treated to a distillation process or the like to separate the high boiling compounds of boron and phosphorous from the chlorosilanes. The high boiling compounds produced through the above described treatment are not decomposed into low boiling compounds by the heat applied after the high boiling compounds having been produced, so that the high boiling compounds can be easily separated from the chlorosilanes through treatment such as distillation. Accordingly, the boron impurity and the phosphorous impurity can be removed with a single process.