CMP Retaining Ring with Asymmetric Tapered Inner Surface
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Solution Overview
Problem
Current chemical mechanical polishing (CMP) processes face challenges in maintaining a uniform material removal profile across the substrate surface due to unpredictable substrate bias during polishing, leading to local non-uniformities.
Innovation Solution
The design of a retaining ring with an annular body featuring tapered and planar surfaces relative to the central axis, along with an array of facets and channels for fluid passage, which helps in distributing the polishing force uniformly and minimizing substrate bias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional retaining ring with a cylindrical inner surface is used, then the substrate can be retained during polishing, but the substrate may be biased unpredictably in an upward or downward direction at contact points, leading to local non-uniformities in the planarization profile
Solution Approach 1:
The inner surface of the retaining ring is designed with asymmetric tapered portions at specific angular positions rather than a symmetric cylindrical surface. This asymmetric geometry creates predictable contact points that apply controlled mechanical bias to the substrate, eliminating the unpredictable upward or downward biasing that occurs with conventional cylindrical surfaces. The tapered portions are strategically positioned to ensure uniform radial and polar material removal across the substrate surface.
2Manufacturing precision
If the inner surface of the retaining ring is made complex with multiple tapered portions and facets, then uniform material removal can be achieved, but the device complexity increases
Solution Approach 1:
Rather than making the entire inner surface complex, the invention applies localized tapered portions and facets only at specific angular positions and depths on the inner cylindrical surface. The majority of the inner surface remains relatively simple, with modifications concentrated in specific zones where contact with the substrate occurs. This localized approach achieves uniform material removal while minimizing overall geometric complexity and manufacturing difficulty.
Data Source
AI summary
Embodiments herein relate to a retaining ring for use in a polishing process. The retaining ring includes an annular body having an upper surface and a lower surface. An inner surface is connected to the upper surface and the lower surface. The inner surface includes one or more surfaces that are used to retain a substrate during processing. The one or more surfaces have an angle relative to a central axis of the retaining ring. The inner surface also includes a plurality of facets. Channels are disposed within the retaining ring to allow passage of a polishing fluid from an inner surface to an outer surface of the retaining ring disposed opposite of the inner surface.