CMP Retaining Ring Interlock Segmentation
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Solution Overview
Problem
Conventional retaining rings for chemical mechanical polishing (CMP) are expensive and require frequent replacement due to wear, often secured with adhesives which complicates refurbishment and can lead to slippage issues.
Innovation Solution
A retaining ring design featuring a plastic lower portion and a more rigid metal or ceramic upper portion, secured with mechanical fasteners, incorporating interlock features and channels for slurry transport, allowing for easier refurbishment and preventing slippage without the need for adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to secure the lower portion to the upper portion, then the retaining ring can be assembled, but the assembly becomes complex and slippage issues occur
Solution Approach 1:
The retaining ring is divided into an upper portion and a lower portion with interlocking features. The lower portion includes protrusions that fit into recesses in the upper portion, creating a segmented design that eliminates the need for adhesives while preventing slippage through mechanical interlocking.
Solution Approach 2:
The adhesive bonding system is replaced with a mechanical fastening system. The interlocking protrusions and recesses provide a purely mechanical connection between the upper and lower portions, eliminating chemical bonding complexity and slippage issues associated with adhesives.
2Loss of substance
If the lower portion is made thinner to reduce material usage, then manufacturing cost decreases, but refurbishment becomes more difficult
Solution Approach 1:
The retaining ring is segmented into replaceable upper and lower portions. The lower portion can be independently removed and replaced without affecting the upper portion, enabling easy refurbishment. The interlocking features facilitate quick detachment and reattachment of the lower portion during maintenance.
3Ease of repair
If mechanical fasteners are used to secure the portions, then refurbishment becomes easier, but the lower portion requires thicker sections at fastener locations
Solution Approach 1:
The lower portion features localized thickened sections at specific azimuthal positions where interlocking protrusions are located. These localized thickness variations provide the necessary structural support for mechanical fastening while maintaining a relatively uniform appearance elsewhere on the lower portion.
4Ease of manufacture
If the retaining ring is designed as a single plastic part, then manufacturing is simpler, but the ring wears away quickly and requires frequent replacement
Solution Approach 1:
The retaining ring uses a composite construction with an upper portion and a lower portion made of different materials optimized for their specific functions. The lower portion contacts the polishing pad and is designed for wear resistance, while the upper portion provides structural support. This composite design extends service life compared to a single-material design.
Solution Approach 2:
The retaining ring is segmented into an upper portion and a lower portion that can be independently replaced. When the lower portion wears out from contact with the polishing pad, only the lower portion needs to be replaced, not the entire retaining ring. This segmentation extends the effective service life of the overall assembly.
Data Source
AI summary
A retaining ring includes an annular lower portion and an annular upper portion. The annular lower portion has a main body with a bottom surface for contacting a polishing pad during polishing, an inner rim projecting upward from the main body, an outer rim projecting upward from the main body and separated from the inner rim by a gap, and a plurality of azimuthally separated interlock features positioned between the inner rim and the outer rim, each interlock feature projecting upwardly from the main body. The annular upper portion has a top surface and a bottom surface and a plurality of azimuthally separated recesses in the bottom surface, the recesses defining thin portions of the upper portion, the plurality of interlock features fitting into the plurality of recesses. The lower portion is a plastic and the upper portion is a material that is more rigid than the plastic.