Polycrystalline Silicon Rod Surface Control via Gas Ejection Velocity
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Solution Overview
Problem
The existing methods for manufacturing polycrystalline silicon, such as the Siemens method, face challenges in uniformly supplying raw material gas to closely packed silicon seed rods, leading to malformation and a decrease in the proportion of silicon rods with smooth surfaces, which are necessary for single crystal silicon production.
Innovation Solution
A method that controls the ejection velocity of the raw material gas by gradually increasing and then decreasing it through stabilizing, shaping, and growing steps, using a branching of gas ejection ports from a single pipe to ensure even supply and prevent thermal stress, allowing for the formation of silicon rods with uniform surface topography without requiring enhanced facilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the amount of raw material gas is increased to supply enough gas to closely packed silicon seed rods, then the supply amount per unit area is improved, but the facility complexity and cost increase
Solution Approach 1:
The gas supply system is segmented into multiple independent gas ejection ports distributed around the reaction furnace. Each port can be controlled independently to eject raw material gas in specific directions, allowing precise gas distribution to closely packed silicon seed rods without requiring complex centralized supply facilities
Solution Approach 2:
Raw material gas is ejected locally at multiple discrete ports positioned strategically around the furnace rather than through a single centralized supply system. This local gas ejection ensures each region receives appropriate gas supply based on local conditions, maintaining uniform deposition without enhancing overall facility complexity
2Manufacturing precision
If the raw material gas supply is increased to maintain supply per unit area as rods grow, then the deposition continues uniformly, but the facility requires enhancement and cost grows
Solution Approach 1:
The gas ejection system is designed to be dynamically adjustable, with each gas ejection port's flow rate and ejection timing independently controllable. This dynamic control allows the system to adapt gas supply to the growing rod dimensions without requiring physical facility enhancements, maintaining deposition uniformity throughout the growth process
Solution Approach 2:
The system controls deposition uniformity by changing operational parameters (gas flow rate, ejection timing, temperature) rather than enhancing facility structure. The gas ejection ports adjust gas supply parameters dynamically to match rod growth, avoiding the need for facility enhancement while maintaining precise manufacturing control
3Productivity
If silicon seed rods are closely packed to increase production capacity, then productivity is improved, but uniform gas supply becomes difficult and surface quality deteriorates
Solution Approach 1:
The gas supply is segmented into multiple discrete ejection ports positioned to target individual or groups of closely packed silicon seed rods. This segmentation allows each rod or row of rods to receive optimized gas supply independently, maintaining uniform deposition and smooth surface quality even when productivity is increased through close packing
Solution Approach 2:
Each gas ejection port provides localized gas supply to specific regions where silicon seed rods are positioned. This local quality control ensures that even closely packed rods receive appropriate gas distribution, preventing surface malformation and maintaining high surface smoothness while achieving high production capacity
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 effectively prevents malformation of silicon rods, increasing the yield of high-quality polycrystalline silicon with smooth surfaces by ensuring uniform gas supply and controlled growth, while maintaining the existing manufacturing apparatuses.
Implementation Method 1
When an electric current is applied from the electrodes to the silicon seed rods, the silicon seed rods are heated due to the resistance.
Implementation Method 2
allowing polycrystalline silicon to deposit on surfaces of the silicon seed rods by pyrolysis and hydrogen reduction of the raw material gas
Implementation Method 3
supplying a raw material gas which is a mixed gas of chlorosilarie gas and hydrogen gas into the reaction furnace thereby bringing the raw material gas into contact with the heated silicon seed rods, and allowing polycrystalline silicon to deposit on surfaces of the silicon seed rods
Data Source
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AI summary
A method for manufacturing polycrystalline silicon with high quality by effectively preventing undesired shape such as giving an rough surface to silicon rods or an irregularity in diameter of the silicon rods. The method for manufacturing polycrystalline silicon includes: an initial stabilizing step of deposition wherein a velocity of ejecting the raw material gas from the gas ejection ports is gradually increased; the shaping step wherein first the ejection velocity is increased at a rate higher than that in the stabilizing step and then the ejection velocity is gradually increased at a rate lower than the previous increasing rate; and a growing step wherein, after the shaping step, the ejection velocity is made slower than that at the end of the shaping step until the end of the deposition.