Polycrystalline Silicon Rod Growth Temperature Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to maintain a high yield and growth rate for polycrystalline silicon production while preventing meltdown and achieving a large diameter of 100 mm or larger, as excessive raw material gas supply at high pressure leads to convection heat transfer issues and temperature imbalances in the Siemens method.
Innovation Solution
The method involves controlling both the current value and raw material gas supply in a reactor at pressures between 0.4 MPa and 0.9 MPa, maintaining surface and center temperatures within specific ranges to prevent meltdown and ensure a smooth surface, with a gas flow rate adjusted to promote deposition and heat balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a large amount of raw material gas is supplied at high pressure to increase growth rate, then the growth rate of polycrystalline silicon increases, but the convection heat transfer from the rod to the gas increases causing the center temperature to rise excessively and meltdown occurs
Solution Approach 1:
The patent applies dynamics by adjusting the current value supplied to the silicon seed rod during the growth process. The current value is increased when the rod diameter is small to promote growth, and then decreased when the rod diameter reaches a certain size to prevent excessive center temperature rise and meltdown. This dynamic adjustment allows the system to adapt to changing conditions and resolve the contradiction between growth rate and meltdown prevention.
Solution Approach 2:
The patent changes the parameter of current value supplied to the silicon seed rod based on the rod diameter. By controlling the current value to be in a first range when the rod diameter is small and in a second range (lower than the first range) when the rod diameter is larger, the system optimizes both growth rate and temperature control, preventing meltdown while maintaining high productivity.
2Productivity
If the current value is increased to maintain surface temperature for high growth rate, then the growth rate increases, but the center temperature rises excessively causing meltdown
Solution Approach 1:
The patent dynamically adjusts the current value based on rod diameter. When the rod diameter is small, a higher current value is applied to maintain surface temperature for high growth rate. When the rod diameter increases, the current value is reduced to prevent excessive center temperature rise, thus avoiding meltdown while maintaining acceptable growth rate.
Solution Approach 2:
The patent applies different current values to different stages of rod growth. The first current value range is used for rods with small diameter to maximize growth, while the second current value range is used for rods with larger diameter to control temperature. This local differentiation of treatment based on rod size resolves the contradiction between growth rate and temperature control.
3Productivity
If excessive raw material gas is supplied to increase deposition rate, then the deposition rate increases, but the ratio of raw material gas contributing to deposition reaction decreases and yield decreases
Solution Approach 1:
The patent optimizes the supply amount of raw material gas based on rod diameter. When the rod diameter is small, a larger supply amount is used to maximize deposition rate. When the rod diameter increases, the supply amount is adjusted to maintain optimal yield. This parameter adjustment resolves the contradiction between deposition rate and yield by matching gas supply to actual deposition needs.
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 allows for efficient growth of polycrystalline silicon rods with diameters of 100 mm or larger, maintaining high yield and growth rate while preventing meltdown, and producing a smooth surface suitable for semiconductors.
Implementation Method 1
supplying electric current to a silicon seed rod in a reactor to make the silicon seed rod to generate heat
Implementation Method 2
polycrystalline silicon is deposited by heat decomposition or hydrogen reduction of the raw material gas
Implementation Method 3
polycrystalline silicon is deposited by heat decomposition or hydrogen reduction of the raw material gas
Implementation Method 4
raw material gas including chlorosilane gas and hydrogen gas is supplied to the reactor to bring the raw material gas into contact with the heated silicon seed rods. On the surface of the heated silicon seed rods, polycrystalline silicon is deposited
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A polycrystalline silicon producing method includes: the first process and the second process. In the first process, a surface temperature is maintained at a predetermined range by adjusting the current value to the silicon seed rod, and the raw material gas is supplied while maintaining a supply amount of chlorosilanes per square millimeter of the surface of the rod in a predetermined range until a temperature of the center portion of the rod reaches a predetermined temperature lower than the melting point of the polycrystalline silicon, and in the second process, a previously determined current value is set corresponding to a rod diameter and the supply amount of the raw material gas per square millimeter of the surface of the rod is decreased to maintain the surface temperature and the temperature of the center portion of the rod at predetermined ranges, respectively.