Flexible Membrane Assembly for CMP Wafer Carrier
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Solution Overview
Problem
Existing wafer carrier configurations during chemical mechanical planarization (CMP) suffer from non-uniform planarization due to wafer distortion and excessive material removal, particularly at the edges, leading to unusable wafers and reduced yield.
Innovation Solution
A flexible membrane assembly in the wafer carrier, comprising a flat flexible membrane, a rigid cylindrical sidewall, and a flexible flange, is used to control backpressure through pressurized air or a bladder, reducing edge effects and vibrations, and allowing for uniform polishing across the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a hard backed wafer carrier configuration is used with rigid surface against wafer backside, then polishing pressure is increased to force wafer surface to polishing pad, but wafer distortion occurs and planarization uniformity deteriorates
Solution Approach 1:
The patent employs a flexible membrane as the backing surface that contacts the wafer backside during CMP. This membrane can conform to the wafer surface topology without causing distortion, replacing the rigid backing plate. The flexible membrane allows uniform pressure distribution while adapting to wafer shape variations, thereby maintaining planarization uniformity without requiring excessive polishing pressure.
Solution Approach 2:
The patent changes the physical state of the backing surface from rigid to flexible. By transforming the backing plate into a flexible membrane, the system can dynamically adjust its compliance to match wafer characteristics, enabling effective polishing at lower pressures while maintaining uniformity across the wafer surface.
2Productivity
If high polishing pressure is applied to conform wafer surface to polishing pad, then material removal rate increases, but excessive material removal at edges occurs and wafer yield decreases
Solution Approach 1:
The flexible membrane backing adapts to the wafer's curved edge profile, distributing polishing pressure more evenly across the wafer surface including the edges. This prevents the concentration of stress at edge regions that occurs with rigid backings, thereby reducing excessive material removal at edges while maintaining acceptable material removal rates across the wafer.
3Ease of manufacture
If a single piece molded membrane assembly is used, then manufacturing complexity is reduced, but dimensional control difficulty increases
Solution Approach 1:
The patent divides the membrane assembly into separate components: the flexible membrane is manufactured independently with controlled dimensions, then assembled to a rigid support structure. This segmentation allows each component to be manufactured with appropriate precision controls - the membrane for flexibility and the support for dimensional stability - while simplifying the overall manufacturing process compared to molding a single complex piece.
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 flexible membrane assembly enhances planarization uniformity, reduces edge effects, and minimizes wafer distortion, resulting in improved polishing consistency and increased wafer yield by maintaining consistent material removal rates across the wafer surface.
Implementation Method 1
A flexible membrane assembly is provided for use in the wafer carrier, upon which pressurized air and/or pressurized bladder act to control wafer backpressure during polishing.
Data Source
AI summary
A flexible membrane assembly for a wafer carrier in a CMP system. The flexible membrane assemble has a flat, flexible membrane joined to a rigid cylindrical sidewall.