Polished Retaining Ring for CMP Microscratch Reduction
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Solution Overview
Problem
Conventional retaining rings in chemical mechanical polishing (CMP) systems introduce microscratches and defects due to loose materials and adherence issues, which become critical as feature sizes shrink below 20 nm, affecting device yield and performance.
Innovation Solution
A retaining ring with a polished inner diameter and grooves is designed to reduce adherence and slurry buildup, featuring a roughness average (Ra) of less than 30 microinches, enhancing slurry release and preventing material accumulation, thereby minimizing defects and improving production yields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional retaining ring is used in CMP system, then the substrate can be held and polished, but microscratches and defects are introduced due to loose materials and adherence issues
Solution Approach 1:
The retaining ring applies local quality by polishing only the inner diameter surface that contacts the substrate to a specific roughness average (Ra) of less than 30 microinches, while other surfaces maintain their original finish. This localized surface treatment prevents material adherence and microscratch formation at the critical substrate-contact interface without requiring complete ring replacement or extensive rework.
Solution Approach 2:
The invention changes the surface roughness parameter of the retaining ring's inner diameter from conventional finishes to a controlled Ra of less than 30 microinches. This parameter modification alters the interaction between the retaining ring and substrate, reducing material adherence and preventing loose particle generation that causes microscratches during polishing operations.
2Object-generated harmful factors
If the inner diameter wall is polished to reduce roughness, then material adherence is reduced, but manufacturing complexity increases
Solution Approach 1:
The retaining ring manufacturing process is segmented into distinct zones: the inner diameter surface receives polished treatment with Ra < 30 microinches, while outer surfaces and structural features maintain conventional manufacturing finishes. This segmentation allows selective application of surface treatment only where substrate contact occurs, minimizing overall manufacturing complexity while achieving the anti-adherence objective.
3Productivity
If conventional retaining rings are used, then production can proceed, but maintenance intervals are frequent due to material buildup
Solution Approach 1:
The retaining ring is pre-polished to Ra < 30 microinches during manufacturing or initial setup, creating a surface that resists material buildup from the outset. This preliminary surface preparation prevents accumulation of polishing slurry and substrate material during production runs, extending the duration between maintenance intervals and improving overall production uptime without requiring additional operational steps.
Data Source
AI summary
A retaining ring and a chemical mechanical planarization system (CMP) are disclosed. In one embodiment, a retaining ring for a polishing system includes a ring-shaped body having a polished inner diameter. The body has a bottom surface having grooves formed therein, an outer diameter wall, and an inner diameter wall, wherein the inner diameter wall is polished to a roughness average (Ra) of less than about 30 microinches (μin).