Magnetic Retaining Ring for CMP Edge Uniformity
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Solution Overview
Problem
Existing retaining rings in chemical mechanical polishing (CMP) processes face challenges such as edge effects, complex design, and inefficient slurry intake and retention, leading to non-uniform polishing and high slurry consumption.
Innovation Solution
A retaining ring assembly with movable teeth and magnets that adjust the gap between the teeth and the polishing pad, allowing for precise control of slurry transport and downforce distribution, reducing edge effects and slurry consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the outer zones of the membrane are spaced more closely together to provide precise pressure control at the outer edge, then edge effect control is improved, but device complexity increases making manufacturing more difficult
Solution Approach 1:
The membrane is divided into multiple discrete zones (e.g., 3-11 zones) with independent pressure control, allowing precise control at the outer edge without requiring excessively close spacing throughout the entire membrane structure
Solution Approach 2:
Different radial zones of the membrane are assigned different functions, with outer zones optimized for edge effect control and inner zones for overall substrate support, allowing each zone to have tailored characteristics rather than uniform design
2Ease of manufacture
If existing retaining rings with fixed grooves are used, then manufacturing is simplified, but slurry intake and retention efficiency decreases leading to high slurry consumption
Solution Approach 1:
The retaining ring incorporates movable teeth that can adjust their position and orientation, allowing the groove configuration to dynamically adapt to different operating conditions and optimize slurry intake and retention efficiency
Solution Approach 2:
The groove dimensions, shape, and configuration are made variable through the movable tooth mechanism, allowing optimization of slurry flow characteristics without requiring multiple fixed designs for different applications
3Device complexity
If existing retaining rings with fixed groove dimensions are used, then design complexity is reduced, but polishing uniformity decreases due to edge effects and scraping
Solution Approach 1:
The movable teeth allow the retaining ring to dynamically adjust its groove configuration during operation, optimizing slurry distribution and preventing edge effects that lead to non-uniform polishing
Solution Approach 2:
The movable tooth mechanism responds to operating conditions and slurry flow patterns, automatically adjusting groove characteristics to maintain optimal polishing uniformity throughout the process
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 improves wafer edge uniformity, simplifies membrane design, and reduces overall slurry consumption by optimizing slurry intake and retention during the CMP process.
Implementation Method 1
a magnet movable vertically along the groove... moving the retainer vertically by exerting a magnetic force on the movable magnet
Data Source
AI summary
A system and method for polishing a substrate, and a retaining ring assembly therefor, are described herein. A retaining ring assembly is configured to be attached to a carrier head. The retaining ring assembly includes a retaining ring including a lower surface, an inner surface, an outer surface and a plurality of grooves, where the lower surface is configured to contact a polishing pad during a polishing process, and each of the plurality of grooves are formed in the lower surface and extend from the inner surface to the outer surface. The retaining ring assembly includes a plurality of retainers, each retainer including a movable tooth at least partially disposed in a respective groove of the retaining ring and moveable relative to the lower surface.