Polycrystalline Silicon Quenching Prevents Phosphorus Buildup
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Solution Overview
Problem
The existing processes for producing polycrystalline silicon rods suffer from phosphorus component buildup in the reaction vessel due to the infiltration of phosphorus-silicon compounds in the discharge gas, which reduces the purity of the obtained silicon, despite quenching the discharge gas from 1000°C to 800°C in less than 0.2 seconds.
Innovation Solution
Quenching the discharge gas from 800°C to 500°C in no longer than 0.1 second to prevent the formation of phosphorus-silicon compounds that are difficult to separate from silane compounds, allowing for the effective reuse of silane gas by maintaining the reaction vessel at high temperatures and using a cooler with spray nozzles to achieve rapid quenching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the discharge gas is quenched from 1000°C to 800°C in not longer than 0.2 seconds, then the residence time in high temperature region is reduced, but phosphorus component still builds up and deposits on polycrystalline silicon rods
Solution Approach 1:
The patent changes the quenching parameters by lowering the final temperature from 800°C to 500°C and reducing the quenching time to 0.1 seconds or less. This parameter optimization prevents phosphorus-silicon compound formation more effectively than the prior art's 800°C quenching temperature.
Solution Approach 2:
The patent applies rapid quenching that rushes through the critical temperature region where phosphorus-silicon compounds form. By quenching from 800°C to 500°C in 0.1 seconds or less, the process skips the dangerous temperature window that allows phosphorus infiltration, preventing compound formation.
2Ease of operation
If the discharge gas is quenched slowly, then the separation of silane compound is easier, but phosphorus-silicon compounds form and contaminate the silane gas
Solution Approach 1:
The patent uses rapid quenching to rush through the temperature region where phosphorus-silicon compounds form, preventing contamination of the silane compound while still allowing easy separation afterward due to the low final temperature.
Solution Approach 2:
The patent optimizes the quenching parameters (temperature and time) to achieve a state where phosphorus-silicon compound formation is suppressed but silane compound remains easily separable through conventional methods.
3Stability of the object's composition
If the quenching time is extended, then the temperature uniformity improves, but phosphorus component infiltrates and forms compounds with silane
Solution Approach 1:
The patent applies ultra-rapid quenching that completes the cooling process in 0.1 seconds or less, rushing through the temperature region where phosphorus infiltration occurs. This prevents phosphorus-silicon compound formation while maintaining sufficient temperature uniformity for process stability.
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 approach effectively suppresses the formation of phosphorus-silicon compounds, enabling the easy separation and reuse of silane gas, thereby maintaining the purity of polycrystalline silicon rods and preventing phosphorus buildup in the reaction vessel.
Implementation Method 1
the discharge gas discharged from the reaction vessel is quenched so that the temperature thereof drops from 800°C down to 500°C in not longer than 0.1 second
Implementation Method 2
depositing polycrystalline silicon on silicon core members arranged being erected in a reaction vessel relying on the chemical vapor-phase deposition method
Implementation Method 3
heating the silicon core members by feeding the electric current through the electrodes
Data Source
Figure 1
AI summary
[Problem] To provide a process for producing polycrystalline silicon, which is capable of effectively preventing the formation of phosphorus-silicon compounds in the discharge gas discharged from the reaction vessel, and makes it possible to reuse a silane compound contained in the discharge gas. [Means for Solution] The process for producing polycrystalline silicon by feeding a reaction gas containing a silane gas and a hydrogen gas into a reaction vessel equipped with silicon core members erected on the electrodes, heating the silicon core members by flowing an electric current thereto to a temperature at which silicon deposits, forming polycrystalline silicon rods by allowing the formed silicon to deposit on the silicon core members, and discharging the discharge gas after the reaction from the reaction vessel, wherein the discharge gas discharged from the reaction vessel is quenched so that the temperature thereof drops from 800°C down to 500°C in not longer than 0.1 second.