Segmented CMP Retaining Ring for Stress Relief
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Solution Overview
Problem
Conventional retaining rings for chemical mechanical polishing (CMP) suffer from internal stress accumulation during use, leading to delamination and reduced working life, and are often limited in material selection due to stress-related issues.
Innovation Solution
A retaining ring design featuring a lower portion with grooves on both surfaces, allowing for increased flexibility and reduced internal stress through matching groove patterns, which can be formed from a variety of materials including injection-molded plastics, and secured with an adhesive layer to prevent slurry accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional retaining ring is used for CMP, then the substrate can be held in place during polishing, but internal stress accumulates leading to delamination and reduced working life
Solution Approach 1:
The retaining ring is divided into multiple circumferential segments that can move relative to each other, allowing stress to be distributed and released rather than accumulating in a monolithic structure. The segments are connected by flexible connections that enable relative movement while maintaining structural integrity.
Solution Approach 2:
The retaining ring transitions from a static, rigid structure to a dynamic structure where segments can move relative to each other. This dynamic capability allows the ring to adapt to stress conditions during polishing, preventing stress accumulation and delamination.
2Strength
If a rigid retaining ring structure is used, then structural strength is maintained, but flexibility is reduced limiting material selection
Solution Approach 1:
By segmenting the retaining ring structure, the patent enables the use of materials with lower individual strength properties while maintaining overall structural strength through the distributed segment architecture. This segmentation allows greater material versatility.
Solution Approach 2:
The flexible connections between segments function similarly to flexible shells, allowing the structure to bend and adapt while maintaining strength. This enables the use of more material options including polymers and composite materials that would be unsuitable for rigid monolithic structures.
3Stability of the object's composition
If grooves are added to the retaining ring to improve flexibility, then stress distribution improves, but device complexity increases
Solution Approach 1:
The segmentation approach inherently creates groove-like features between segments that facilitate stress distribution and flexibility. This achieves the stress distribution benefit of grooves while the segmentation framework provides a systematic method that doesn't significantly increase complexity beyond the basic segmented architecture.
Data Source
AI summary
A two part retaining ring is described that has a lower ring and an upper ring. The lower ring contacts a polishing surface during chemical mechanical polishing. The upper surface and the lower surface of the lower ring have thick and thin subportions to increase the flexibility of the lower ring.