Wafer Holder Cavity Precision via Layered Tolerance Segmentation
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Solution Overview
Problem
Current wafer holders in polishing machines lack precision and durability, leading to potential wafer shattering and reduced service life due to inadequate cavity size and material thickness tolerances.
Innovation Solution
A method of manufacturing wafer holders with a frame having cavities matching the wafer's cross-sectional footprint, using thermoset or thermoplastic materials with precise thickness tolerances, and permanently affixing a polymer film pad to improve wafer support and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional wafer holders are used with standard thickness tolerances, then manufacturing cost is reduced, but wafer precision and service life deteriorate due to inadequate cavity size and material thickness variations
Solution Approach 1:
The wafer holder is divided into multiple layers (first layer, second layer, third layer) that are manufactured separately and then assembled. This segmentation allows each layer to be manufactured with precise thickness tolerances using standard processes, while the overall assembly achieves the required precision through controlled combination of layers with complementary tolerances.
Solution Approach 2:
The invention changes the thickness parameter of each layer to have opposite tolerance extents (e.g., first layer at +0.002/-0.000, second layer at +0.000/-0.002). This parameter adjustment ensures that when layers are assembled, the tolerances complement each other, resulting in a final assembly with reduced cumulative tolerance and improved precision without requiring ultra-precise manufacturing for each individual layer.
2Manufacturing precision
If tighter thickness tolerances are applied to all frame layers, then wafer holder precision is improved, but manufacturing cost and complexity increase significantly
Solution Approach 1:
Instead of applying tight tolerances to all layers, the invention applies partial precision control by using opposite tolerance extents on specific layers. This partial action approach achieves the necessary cavity depth consistency without the excessive cost and reduced productivity that would result from tightening tolerances on all layers uniformly.
Solution Approach 2:
The thickness tolerance parameters of different layers are changed to have opposite signs (one layer positive tolerance, another negative tolerance). This parameter transformation allows the cumulative tolerance to be reduced while maintaining standard manufacturing capabilities, thereby preserving productivity while achieving the required precision.
3Reliability
If the cavity footprint is reduced to match only the essential wafer area, then material usage is reduced, but wafer support precision deteriorates leading to potential shattering
Solution Approach 1:
The cavity structure is segmented into multiple layers, each contributing to the overall support surface. This layered segmentation allows the cavity footprint to extend across the entire wafer area for maximum support and reliability, while the material usage is optimized by having each layer provide partial coverage that accumulates to full support without excessive material in any single layer.
Data Source
AI summary
A method of manufacturing a wafer holder, the wafer holder having a frame having at least one cavity capable of receiving and supporting a wafer grown from an ingot to be polished in a polishing machine, the at least one cavity having a cross sectional footprint at least equal to a cross sectional footprint of the wafer, the wafer having a thickness to cross sectional area ratio of 0.001 per unit length or less, a polymer film pad being permanently affixed in the at least one cavity, including cutting a frame from a layer of a thermoset or thermoplastic material having a thickness tolerance and measuring a thickness of the frame at at least one location thereon. The method further includes forming a cavity in the frame having a predetermined depth, and permanently affixing a polymer film pad in the cavity.