Segmented Retaining Ring for CMP Wear Reduction
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Solution Overview
Problem
Retaining rings for carrier heads in chemical mechanical polishing (CMP) are expensive and require frequent replacement due to wear, with limited options for suitable plastic compositions that balance rigidity, wear rate, and chemical resistance.
Innovation Solution
A retaining ring design featuring a detachable, annular lower portion composed of multiple arcuate segments made from a durable plastic, which can be easily assembled and replaced, allowing the use of less expensive materials and extending the ring's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retaining ring is made from a single durable plastic material to resist wear, then wear resistance is improved, but material cost and manufacturing complexity increase due to limited suitable plastic compositions
Solution Approach 1:
The retaining ring is divided into two distinct portions: an upper portion that can be made from less expensive materials and a lower portion that contacts the polishing pad and requires wear-resistant properties. This segmentation allows each portion to be optimized independently for its specific functional requirements.
Solution Approach 2:
Different material properties are applied to different portions of the retaining ring. The lower portion has enhanced wear resistance properties while the upper portion uses standard materials, matching material properties to local functional demands rather than using a uniform material throughout.
2Strength
If a retaining ring is made from metal to provide rigidity, then structural strength is improved, but wear rate increases due to contact with the polishing pad
Solution Approach 1:
The retaining ring is divided into an upper portion (which can be metal for rigidity) and a lower portion (which contacts the polishing pad and requires wear resistance). This allows the structural support function to be separated from the wear-resistant function.
Solution Approach 2:
The retaining ring uses composite construction with different materials for different portions. The upper portion may use metal for rigidity while the lower portion uses wear-resistant plastic or composite materials, combining the advantages of different material types in a single component.
3Reliability
If the entire retaining ring is replaced when worn, then functionality is restored, but cost and time increase due to replacement of unworn portions
Solution Approach 1:
The retainable ring is divided into an upper portion and a lower portion that can be independently removed and replaced. This allows only the worn lower portion to be replaced while retaining the unworn upper portion, reducing replacement cost and time.
Solution Approach 2:
Instead of discarding the entire retaining ring when the lower portion wears, the design allows recovery and reuse of the upper portion. Only the worn lower portion is discarded, maximizing material utilization and reducing waste.
4Strength
If a single-piece retaining ring design is used, then structural integrity is maintained, but ease of repair deteriorates as worn segments cannot be selectively replaced
Solution Approach 1:
The retaining ring is divided into separable upper and lower portions that can be independently removed and replaced. This segmentation enables selective repair of only the worn lower portion while maintaining the ability to restore structural integrity through proper reassembly.
Solution Approach 2:
The design transitions from a static single-piece structure to a dynamic modular structure where portions can be independently removed, replaced, or maintained. This allows the system to adapt to wear patterns and enable selective maintenance.
Data Source
AI summary
A retaining ring includes a generally annular upper portion having a top surface configured to be connected to a base of a carrier head and a lower surface, and a plurality of substantially identical arcuate segments detachably secured to the upper portion to form an annular lower portion. Each of the arcuate segments has an upper surface that abuts the lower surface of the upper portion and a bottom surface for contacting a polishing pad during polishing.