Elastic Membrane Concentric Walls Wafer Polishing Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In semiconductor wafer polishing, the existing substrate holding apparatuses face challenges in achieving uniform polishing rates across the wafer surface due to step-like pressure differences between adjacent pressurizing areas, leading to irregular polishing profiles and reduced yield.
Innovation Solution
The elastic membrane in the substrate holding apparatus is configured with concentrically arranged circumferential walls to define central, edge, and intermediate pressurizing areas, with the area width of at least one intermediate pressurizing area set to maintain a polishing rate responsive width within 20% to 100% of the maximum variation, ensuring consistent polishing across the wafer surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple concentric pressure chambers are provided to apply different pressures at respective pressurizing areas, then polishing rate uniformity can be improved, but step-like pressure differences between adjacent chambers cause irregular polishing profiles
Solution Approach 1:
The elastic membrane is divided into multiple concentric pressure chambers (central, intermediate, and edge chambers) that can be independently pressurized. This segmentation allows different regions of the wafer to receive different polishing pressures, enabling uniform polishing rate control across the wafer surface while maintaining independent pressure control for each region.
Solution Approach 2:
Each pressure chamber is designed with specific local characteristics - the central chamber has a different pressure control mechanism than the intermediate and edge chambers. This local quality differentiation allows optimization of polishing conditions for each specific region of the wafer, addressing the technical contradiction by enabling both uniform polishing rate and region-specific pressure control.
2Manufacturing precision
If the area width of intermediate pressurizing areas is increased to maintain polishing rate responsive width, then polishing rate distribution range is narrowed, but device complexity increases
Solution Approach 1:
The invention optimizes the area width parameter of intermediate pressurizing areas to a specific range (2-15mm for 300mm wafers, 2-26mm for 450mm wafers). By controlling this geometric parameter, the polishing rate responsive width is maintained within 20%-100% of the maximum variation, achieving narrow polishing rate distribution range without requiring excessive structural complexity.
Solution Approach 2:
Instead of making all intermediate pressurizing areas extremely narrow to minimize complexity, the invention applies partial optimization by setting area widths within a practical range (2-15mm or 2-26mm). This partial action approach achieves sufficient surface uniformity improvement while avoiding unnecessary device complexity that would result from making all areas excessively narrow.
3Manufacturing precision
If the elastic membrane is made more flexible to accommodate pressure variations, then polishing rate control is improved, but membrane strength decreases
Solution Approach 1:
The elastic membrane is constructed as a composite structure combining a rubber-based elastomer with reinforcing fibers (such as glass fibers, carbon fibers, or aramid fibers). This composite construction provides both the flexibility needed for precise polishing rate control through pressure variation and the strength required to withstand the mechanical stresses during polishing operations.
Solution Approach 2:
The invention employs a thin-film elastic membrane design that maintains flexibility for precise pressure control while using high-strength materials. The membrane thickness and material selection are optimized to provide sufficient flexibility for polishing rate control without compromising the strength needed to handle wafer polishing forces.
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 narrows the range of polishing rate distribution, enhancing surface uniformity and improving yield by maintaining consistent polishing rates across the wafer surface, even when area widths vary.
Implementation Method 1
by controlling pressures of pressurized fluid supplied to the respective pressure chambers, the semiconductor wafer is pressed against the polishing surface under different pressures at respective pressurizing areas
Implementation Method 2
a plurality of concentrically circumferential walls configured to define a plurality of pressurizing areas for pressing the substrate
Data Source
AI summary
An elastic membrane is used in a substrate holding apparatus for holding a substrate such as a semiconductor wafer and pressing the substrate against a polishing surface. The elastic membrane includes a plurality of concentrically circumferential walls configured to define a plurality of pressurizing areas for pressing the substrate. The pressurizing areas includes a central pressurizing area located at a central part of the elastic membrane, an annular edge pressurizing area located at the outermost part of the elastic membrane, and a plurality of intermediate pressurizing areas located between the central pressurizing area and the annular edge pressurizing area. The area width of at least one of the intermediate pressurizing areas is set in a range to allow a polishing rate responsive width not to vary even when the area width is varied.