Faceted CMP Retaining Ring for Wear and Thickness Uniformity
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Solution Overview
Problem
Conventional retaining rings in chemical mechanical polishing (CMP) systems wear away quickly due to contact with the polishing pad, leading to inefficient substrate planarization and reduced lifetime, resulting in angular asymmetry and uneven thickness in polished substrates.
Innovation Solution
The design of a retaining ring with an annular body featuring multiple planar facets, inwardly-extending projections, or regions with different surface textures and tilts, which distributes pressure and reduces wear by allowing the substrate to contact the ring at multiple points, improving thickness uniformity and extending the ring's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the retaining ring contacts the polishing pad during CMP, then the substrate can be retained and pressed against the polishing pad, but the retaining ring wears away quickly and has reduced lifetime
Solution Approach 1:
The retaining ring is divided into multiple contact regions around its circumference, with each region having faceted surfaces that contact the substrate at different locations. This segmentation distributes the contact pressure and wear across multiple areas, preventing rapid wear at any single point and extending the retaining ring's service life while maintaining effective substrate retention.
2Power
If the retaining ring contacts the polishing pad, then the substrate can be pressed against the polishing pad for planarization, but angular asymmetry and uneven thickness occur in the polished substrate
Solution Approach 1:
Different regions of the retaining ring's inner surface are provided with faceted contact surfaces oriented at different angles and positions. This creates local variations in contact characteristics that distribute the pressing force more uniformly across the substrate surface, preventing angular asymmetry and improving thickness uniformity while maintaining adequate pressing force for effective planarization.
Data Source
AI summary
Some implementations of a retaining ring has an inner surface having a first portion formed of multiple planar facets and a second portion that adjoins the first portion along a boundary and includes a frustoconical surface that is sloped downwardly from outside in. Some implementations of the retaining ring have a crenellated or serpentine inner surface, and/or an inner surface with alternating region of different surface properties or different tilt angles.