Polycrystalline Silicon Rod Fallover Reduction
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Solution Overview
Problem
The existing processes for producing polycrystalline silicon, such as the Siemens process, experience high fallover rates of silicon rods due to abrupt changes in reaction gas inflow velocities, leading to economic damage and contamination, despite efforts to optimize flow conditions and electrode designs.
Innovation Solution
A process that involves terminating polycrystalline silicon deposition when rods reach a desired diameter, removing and replacing them, and conducting a thorough cleaning of the reactor bottom plate with at least two cleaning media in different physical states before new rods are installed, specifically using a combination of gaseous, liquid, or solid cleaning agents to reduce fallover rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the inflow velocity of reaction gas is increased sharply to improve gas supply to support bodies, then the supply of reaction gas is improved, but the fallover rate of rods increases
Solution Approach 1:
The patent applies dynamics by making the nozzle configuration adaptive rather than static. The proportion of closed nozzles is adjusted as a function of process time or rod diameter, allowing the gas supply system to dynamically adapt to changing conditions during deposition. This prevents abrupt velocity changes that cause rod fallover while ensuring adequate gas supply to all rods including those in upper regions.
Solution Approach 2:
The patent changes physical parameters of the gas supply system by adjusting the proportion of closed nozzles based on process time or rod diameter. This parameter adjustment ensures optimal gas distribution throughout the reactor volume, maintaining stable flow conditions that prevent rod fallover while providing sufficient reaction gas to support bodies of varying sizes.
2Quantity of substance
If nozzles are adjusted during deposition to ensure optimal gas supply to upper regions, then gas supply is improved, but the fallover rate increases due to abrupt velocity changes
Solution Approach 1:
The patent implements a dynamic nozzle control system where the proportion of closed nozzles changes continuously or stepwise during the deposition process. This dynamic adjustment ensures that gas supply to upper regions remains optimal as rods grow, while avoiding abrupt velocity changes that would destabilize the rods and cause fallover.
Solution Approach 2:
The patent modifies the operational parameters of the gas supply system by varying the proportion of closed nozzles as a function of process time or rod diameter. This parameter change strategy maintains adequate gas distribution to upper regions while preventing the abrupt flow velocity changes that lead to rod instability and fallover.
3Productivity
If reaction gas inflow velocity is increased to improve deposition efficiency, then deposition efficiency is improved, but rod stability deteriorates leading to increased fallover
Solution Approach 1:
The patent applies dynamics by implementing a progressively closing nozzle system that adjusts gas flow distribution during deposition. This dynamic approach maintains rod stability by avoiding abrupt velocity increases, while still achieving efficient deposition through optimized gas supply to support bodies throughout the process.
Solution Approach 2:
The patent changes the operational parameters of the gas supply system by adjusting the proportion of closed nozzles during deposition. This parameter adjustment ensures that deposition efficiency is maintained through adequate gas supply, while rod stability is preserved by preventing abrupt flow velocity changes that would cause fallover.
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 described cleaning process significantly reduces the fallover rate of polycrystalline silicon rods by ensuring a clean and stable reactor environment, minimizing contamination and maintenance costs, and maintaining uniform growth patterns.
Implementation Method 1
introducing a reaction gas comprising one or more silicon-comprising components and optionally hydrogen via nozzles into a reactor comprising support bodies heated by direct passage of current to deposit solid silicon on the support bodies
Implementation Method 2
support bodies heated by direct passage of current
Data Source
AI summary
The rate of rod fallover in the production of polycrystalline silicon by the Siemens process is sharply reduced by cleaning the Siemens reactor base plate by at least a two-step procedure comprising suctioning the base plate in one step, and subsequently cleaning with liquid or solid cleaning medium in a second step, between each phase of rod removal and new support body installation.