Source Gas Nozzle Layout for Uniform Polycrystalline Silicon Deposition
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Solution Overview
Problem
In the production of polycrystalline silicon using the Siemens method, increasing the reaction temperature to improve productivity leads to the occurrence of popcorn-like surface irregularities due to unstable chlorosilane supply, resulting in non-uniform silicon rod thickness and shape failures.
Innovation Solution
The method involves using a reaction furnace with source gas supply nozzles positioned inside an imaginary concentric circle with a center at the furnace's center, creating a forced convection flow pattern that reduces the thickness of the boundary layer between the gas and solid phases, thereby suppressing popcorn occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the reaction temperature is increased to improve productivity, then the deposition speed of polycrystalline silicon is improved, but the occurrence of popcorn and surface irregularities increases due to unstable chlorosilane supply
Solution Approach 1:
The invention changes the physical parameters of the source gas supply system by adjusting nozzle diameter, number of nozzles, and supply pressure to optimize chlorosilane delivery. This ensures stable supply rates even at high reaction temperatures, preventing popcorn formation while maintaining high deposition speeds.
Solution Approach 2:
The invention divides the single source gas supply into multiple nozzles distributed across the reactor bottom surface. This segmentation ensures uniform chlorosilane distribution to multiple silicon rod surfaces simultaneously, preventing supply instability and popcorn occurrence during high-temperature deposition.
2Productivity
If the number of silicon core wires is increased to increase production capacity, then the total polycrystalline silicon output is improved, but the source gas supply to each rod becomes insufficient causing uneven deposition
Solution Approach 1:
The invention segments the source gas supply system into multiple nozzles (typically 9-25 nozzles) distributed across the reactor bottom surface. Each nozzle serves specific silicon rods, ensuring that even when the number of rods is increased, each rod receives adequate and uniform chlorosilane supply for consistent deposition.
Solution Approach 2:
The invention implements local optimization by positioning nozzles at specific locations and angles tailored to serve specific regions of the reactor. This local quality approach ensures that each area with silicon rods receives appropriate gas supply, maintaining deposition uniformity across all rods regardless of total rod count.
3Productivity
If the source gas supply amount is increased to maintain high deposition speed, then productivity is improved, but the source gas becomes insufficient for all silicon rod surfaces causing popcorn
Solution Approach 1:
The invention segments the total source gas flow into multiple smaller flows through distributed nozzles. This allows the total gas supply amount to be maintained at levels sufficient for high deposition speeds, while each individual nozzle delivers a controlled, stable amount of gas to its designated area, preventing supply instability and popcorn formation.
Solution Approach 2:
The invention optimizes multiple parameters simultaneously including nozzle diameter (0.5-2.0mm), supply pressure (0.1-0.5MPa), and nozzle-to-rod distance (50-200mm) to achieve stable gas distribution. These parameter changes ensure that high total gas flow rates can be maintained while each local supply point operates in a stable regime.
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 occurrence of popcorn by adjusting the kinetic energy of the source gas, ensuring uniform deposition and improving the productivity and energy efficiency of polycrystalline silicon production.
Implementation Method 1
creating a forced convection flow pattern that reduces the thickness of the boundary layer between the gas and solid phases
Implementation Method 2
vapor-phase growing the polycrystalline silicon on the surface of the silicon core wire with a CVD method
Implementation Method 3
Both the ends of the silicon core wires of the square arch shape (U-shape) are fixed to a pair of metal electrodes
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
In a method according to the present invention, an occurrence ratio of popcorn is suppressed by adjusting kinetic energy of a source gas supplied to a reaction furnace for producing polycrystalline silicon with a Siemens method (flow velocity and a supply amount of the source gas in source gas supply nozzle ejection ports). Specifically, in performing deposition reaction of the polycrystalline silicon under a reaction pressure of 0.25 MPa to 0.9 MPa, when flow velocity of the source gas in gas supply ports of the source gas supply nozzles (9) is represented as u (m/sec), a source gas supply amount is represented as Q (kg/sec), and an inner volume of the reaction furnace (100) is represented as V (m3), values of u and Q of each of the source gas supply nozzles(9) are set such that a total ∑(Q×u2/V) of values Q×u2/V is equal to or larger than 2500 (kg/m·sec3).