High-Temperature Bushing Assembly for Substrate Support
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Solution Overview
Problem
Conventional bushings for support pins in large area substrate processing systems fail at high temperatures due to low melting points and complex designs, leading to contamination, increased maintenance costs, and reduced throughput.
Innovation Solution
A high-temperature slide bushing assembly with a tubular body and ceramic rings, designed to reduce contact points with the support pin to minimize friction and thermal expansion issues, using materials with low coefficients of thermal expansion to ensure reliability and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional slide bushings made from low melting point materials like PTFE are used, then the bushing is easy to manufacture and provides lateral support, but the bushing fails at temperatures above 250°C due to material softening and melting
Solution Approach 1:
The bushing is constructed from a composite of ceramic particles (alumina, silica, zirconia) dispersed in a metal matrix (invar, monel, inconel). This composite structure combines the high temperature stability and low thermal expansion of ceramics with the structural integrity and manufacturability of metals, enabling operation above 250°C while maintaining ease of manufacture through conventional metalworking processes
Solution Approach 2:
The invention changes the material parameters by selecting a metal matrix with specific thermal expansion properties (invar, monel, inconel) that match the ceramic particles, creating a composite with minimized thermal expansion. This parameter matching allows the bushing to maintain dimensional stability at high temperatures where conventional materials would soften or melt
2Reliability
If roller bushings with bearings and rollers are used, then lateral support is provided, but the device becomes expensive to produce and prone to failure due to complex moving parts
Solution Approach 1:
The invention extracts and eliminates the complex moving parts (bearings, rollers) from the bushing design. By using a simple tubular structure with an aperture, the design removes all moving components while maintaining the lateral support function through the rigid composite material structure, thereby reducing complexity and eliminating failure points associated with moving parts
Solution Approach 2:
The bushing is segmented into distinct functional zones: a tubular body providing structural support, an aperture for the support pin, and embedded ceramic particles providing thermal stability. This segmentation allows each component to perform its specific function optimally without requiring complex interactions between moving parts
3Reliability
If roller bushings with multiple contact points are used, then lateral support is provided, but friction between the support pin and bushing creates unwanted particles that contaminate the substrate
Solution Approach 1:
The inner surface of the bushing aperture is treated with a different local quality than the outer surface. The inner surface is polished or coated to provide low friction and minimal particle generation, while the outer surface maintains the structural properties of the composite material. This local differentiation reduces substrate contamination from friction particles while maintaining overall bushing reliability
4Ease of operation
If conventional bushings are used in high temperature environments, then support pin movement is facilitated, but thermal expansion causes increased friction and binding leading to device failure
Solution Approach 1:
The invention explicitly addresses thermal expansion by using a composite material where the metal matrix (invar, monel, inconel) has low thermal expansion properties that match the ceramic particles. This thermal expansion matching prevents differential expansion between components, eliminating friction and binding that would occur in conventional single-material bushings at high temperatures
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 solution enhances device reliability and reduces production costs by up to 50% while minimizing substrate contamination and downtime, maintaining performance in environments above 250°C.
Implementation Method 1
designed to reduce contact points with the support pin to minimize friction and thermal expansion issues
Implementation Method 2
minimize friction and thermal expansion issues, using materials with low coefficients of thermal expansion
Data Source
AI summary
A bushing assembly for supporting a substrate within a processing chamber is generally provided. In one aspect, the bushing assembly comprises a tubular body having an outer perimeter and an aperture extending therethrough, a first ring having a first inner edge, the first ring disposed in the aperture in an upper portion of the tubular body, and a second ring having a second inner edge, the second ring disposed in the aperture in a lower portion of the tubular body. In another aspect, the first inner edge has a first radius of curvature, and the second inner edge has a second radius of curvature. In another aspect, a first inner edge diameter, a second inner edge diameter, the first radius of curvature, and the second radius of curvature are selected such that a support pin extending through the aperture contacts the bushing assembly on at most two points.