Slidable Carbon Electrode for Polysilicon Rod Thermal Stress
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Solution Overview
Problem
Conventional Siemens method for manufacturing polycrystalline silicon rods experiences cracks and breaks due to inhibited expansion and contraction in horizontal directions, leading to thermal stress and contamination issues, with existing solutions being complex, expensive, or insufficient in preventing such failures.
Innovation Solution
A carbon electrode design featuring a slidable upper electrode with a hole or recess configuration that allows movement in all directions, providing a gap for expansion and contraction, made of graphite with low friction to prevent cracks and breaks during vapor phase growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the polycrystalline silicon rod is secured rigidly to metal electrodes, then structural stability is improved, but thermal stress causes cracks and breaks
Solution Approach 1:
The patent applies the dynamics principle by making the electrode holder slidable on the electrode surface, allowing the holder to move dynamically in response to thermal expansion and contraction of the silicon rod. This sliding mechanism enables the system to adapt to thermal changes while maintaining structural support, preventing cracks and breaks caused by rigid constraints.
Solution Approach 2:
The patent applies parameter changes by modifying the friction characteristics of the contact surface between the electrode holder and electrode. By controlling the friction coefficient to be 0.3 or less, the system allows sufficient movement to accommodate thermal expansion while maintaining adequate contact for electrical conduction and structural support.
2Reliability
If the electrode holder is made slidable to allow thermal expansion, then rod integrity is improved, but electrical contact stability deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the friction coefficient of the contact surface to 0.3 or less. This parameter adjustment allows the holder to slide freely enough to accommodate thermal expansion and contraction, while maintaining sufficient contact pressure for stable electrical conduction between the holder and electrode.
3Device complexity
If conventional mounting tools are used, then device complexity is reduced, but prevention of cracks and breaks is insufficient
Solution Approach 1:
The patent applies the dynamics principle by introducing a sliding mechanism to the electrode holder, enabling it to move in response to thermal changes. This simple dynamic adjustment significantly improves crack prevention capability without adding complex structures such as springs or multiple components.
Solution Approach 2:
The patent applies parameter changes by controlling the friction coefficient of the contact surface to 0.3 or less. This parameter optimization enables the holder to slide smoothly during thermal expansion and contraction, providing effective crack prevention through a simple modification rather than a complex structural change.
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 carbon electrode design effectively prevents cracks and breaks in polycrystalline silicon rods by allowing all-directional expansion and contraction, reducing thermal stress and contamination, thereby enhancing productivity and operational efficiency.
Implementation Method 1
a coefficient of static friction of a contact surface between the upper electrode and the lower electrode is 0.3 or less
Implementation Method 2
a temperature difference occurs between a center and a surface in a growing direction (radial direction) of the silicon rod during or after vapor phase growth, and this causes stress by thermal expansion or contraction of the polycrystalline silicon rod
Implementation Method 3
a method of bringing a material gas containing chlorosilane into contact with a heated silicon core to grow polycrystalline silicon from vapor phase on a surface of the silicon core using a CVD (Chemical Vapor Deposition) method
Data Source
AI summary
The upper electrode 31 has a hole 35 extending from an upper surface 33 to a lower surface 34, a bolt 36 is inserted from the upper surface 33 of the upper electrode 31 into the hole 35, and secured in a lower electrode 32 by a screw. A gap 51 between an inside of the hole 35 and a straight body portion of the bolt 36 allows the upper electrode 31 to slide in all directions in a placement surface (upper surface of the lower electrode 32 in contact with the lower surface 34 of the upper electrode 31 in FIG. 2) that is a contact surface with an upper surface of the lower electrode 32, thereby providing an effect of preventing occurrence of a crack or a break in a U rod that can be expanded and contracted in all directions during a vapor phase growth process.