Polysilicon Seed Rod Electrode Thermal Management
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Solution Overview
Problem
In the Siemens process for manufacturing polycrystalline silicon, the deposited material often peels off from the lower end of silicon seed rods due to self-weight, potentially damaging the reactor and causing short-circuits, and insufficient deposition occurs due to cooled electrode holders.
Innovation Solution
A manufacturing apparatus with a carbon electrode and an electrode holder featuring a coolant passage, a heat cap, and a cap protector to maintain high temperature and prevent excessive cooling of the seed rod holding member, ensuring uniform deposition on the entire surface of the silicon seed rod, including the lower end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If electrode holders are cooled to prevent overheating, then electrode temperature control is improved, but polycrystalline silicon deposition on the lower end portion of silicon seed rods becomes insufficient
Solution Approach 1:
The electrode is divided into multiple sections: the electrode holder (cooled), the intermediate portion (transition zone), and the seed rod holding portion (heated). This segmentation allows different temperature zones to coexist, enabling both electrode temperature control and sufficient deposition on the seed rod lower end.
Solution Approach 2:
The intermediate portion of the electrode acts as a thermal intermediary between the cooled electrode holder and the heated seed rod holding portion. It gradually transitions the temperature, preventing excessive cooling from reaching the deposition zone while maintaining electrode holder temperature control.
2Productivity
If silicon seed rods are heated for polycrystalline silicon deposition, then deposition rate is improved, but deposited material may peel off due to self-weight and cause short-circuits
Solution Approach 1:
The deposited polycrystalline silicon on the lower end portion of the silicon seed rod acts as a counterweight that reinforces the structural integrity. By ensuring sufficient deposition on the lower end, the weight of the deposited material itself helps prevent peeling off, counteracting the gravitational force that causes detachment.
Solution Approach 2:
The apparatus ensures that polycrystalline silicon is deposited on the lower end portion of the silicon seed rod before the main deposition process on the upper portion. This preliminary deposition creates a strong base that prevents peeling during subsequent deposition and operation.
3Temperature
If electrode holders are made with coolant passages for temperature control, then electrode overheating is prevented, but device complexity increases
Solution Approach 1:
The electrode holder serves multiple functions: it provides mechanical support for the electrode, acts as a coolant passage for temperature control, and maintains the electrode in the correct position. By combining these functions into a single component, the overall device complexity is reduced despite the added cooling capability.
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 design allows for complete and stable deposition of polycrystalline silicon on the silicon seed rods, preventing damage and short-circuits, while enabling the reuse of electrode components and improving manufacturing productivity.
Implementation Method 1
a coolant passage in which coolant medium flows therein is formed in the electrode holder
Implementation Method 2
a heat cap which is provided between the seed rod holding member and the electrode holder
Implementation Method 3
Electric current is supplied to the silicon seed rods via the electrodes, so that the silicon seed rods are heated by the electric resistance
Implementation Method 4
polycrystalline silicon is deposited on the surface of the silicon seed rods by thermal decomposition and hydrogen reduction of the raw-material gas
Implementation Method 5
polycrystalline silicon is deposited on the surface of the silicon seed rods by thermal decomposition and hydrogen reduction of the raw-material gas
Data Source
AI summary
A manufacturing apparatus of polycrystalline silicon products polycrystalline silicon by depositing on a surface of a silicon seed rod by supplying raw-material gas to the heated silicon seed rod provided vertically in a reactor, includes: an electrode which holds the silicon seed rod and is made of carbon; an electrode holder which holds the electrode, and cooled by coolant medium flowing therein, wherein the electrode includes: a seed rod holding member which holds the silicon seed rod; a heat cap which is provided between the seed rod holding member and the electrode holder; and a cap protector having a ring-like plate shape, which covers an upper surface of the heat cap, and in which a through hole penetrating the lower-end portion of the seed rod holding member is formed.