Insulating Ring and Sealing Elements for CVD Electrode Holders
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Solution Overview
Problem
Existing sealing and insulation systems in CVD reactors for polycrystalline silicon deposition are prone to thermal stress, leading to premature failure, leaks, and ground faults due to the limitations of materials like PTFE and ceramic rings, which crack or flow under high temperatures, compromising the integrity of the reactor and the quality of silicon deposition.
Innovation Solution
A device with an electrically insulating ring made of a material with specific thermal conductivity and bending strength, combined with separate sealing elements placed in grooves within the insulating ring or base plate, allows for improved thermal and mechanical protection, ensuring reliable sealing and insulation between the electrode holder and base plate, even under high-temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sealing element is used between the electrode holder and base plate, then the structure is simple, but thermal stress causes premature failure and leaks
Solution Approach 1:
The sealing system is divided into multiple separate sealing elements positioned at different locations between the electrode holder and base plate. This segmentation allows each sealing element to independently handle thermal stress and deformation, preventing single-point failure and maintaining sealing integrity under high-temperature conditions.
Solution Approach 2:
Different sealing elements are positioned at specific locations where thermal stress and leakage risks are highest. Each sealing element is strategically placed to address local thermal and mechanical conditions, providing targeted protection against leakage and thermal degradation at critical interfaces.
2Reliability
If ceramic rings are used for insulation, then electrical insulation is provided, but they crack under high temperature leading to ground faults
Solution Approach 1:
The sealing and insulation system uses composite material construction combining ceramic rings for electrical insulation with multiple sealing elements made of temperature-resistant materials. This composite approach allows the system to simultaneously provide electrical insulation and withstand high temperatures without cracking or failing.
Solution Approach 2:
The ceramic rings are designed with predetermined stress distribution features and are positioned with clearance to accommodate thermal expansion. This beforehand cushioning prevents thermal shock-induced cracking by allowing controlled movement and stress relief before failure can occur.
3Reliability
If PTFE sealing elements are used, then sealing is achieved, but they flow under thermal stress causing short circuits
Solution Approach 1:
The sealing system uses multiple sealing elements with different material properties and cross-sectional geometries positioned at different locations. This allows the system to maintain sealing function while distributing thermal stress across multiple components, preventing any single element from undergoing excessive flow or deformation that would cause short circuits.
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 configuration enhances the service life of the reactor by reducing thermal stress on sealing elements, maintaining the minimum distance between the electrode holder and base plate, and preventing electrical flashovers, thereby increasing the reactor's operational reliability and reducing maintenance costs.
Implementation Method 1
an electrically insulating ring (2) made of a material with a specific thermal conductivity at room temperature of 0.2 - 50 W/mK
Implementation Method 2
reducing thermal stress on sealing elements
Implementation Method 3
a reaction gas containing hydrogen and one or more silicon-containing components is introduced into the reactor, which is equipped with carrier media heated by direct current flow. Solid silicon is then deposited on these carrier media.
Implementation Method 4
heated by direct current flow
Implementation Method 5
leakage through diffusion via the sealing material itself must also be taken into account
Data Source
Figure 1
Figure 2~3
Figure 4a
AI summary
The invention relates to a device for insulating and sealing electrode holders in CVD reactors, comprising an electrode that is suitable for receiving a filament rod and arranged on an electrode holder made of an electrically-conductive material, mounted in a recess of a base plate, wherein an electrically-insulating ring is provided between the electrode holder and base plate, said ring being made of a material with a specific heat conductivity at room temperature of between 0.2 and 50 W/mK, a minimum flexural strength of greater than 120 MPa, and a specific electrical resistance at room temperature of greater than 109 Ωcm, wherein at least two annular sealing elements are provided for sealing between the electrode holder and base plate, the electrically-insulating ring or the electrode holder or the base plate having at least one groove in which a first sealing element is secured, and at least one second sealing element that is not secured in a groove being provided between the electrically-insulating ring and the base plate or between the electrically-insulating ring and the electrode holder.