CMP Carrier Head Retaining Rings for Edge Polishing Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in achieving uniform polishing rates across the substrate, particularly at the edge exclusion region, leading to reduced yield and unsuitability for device manufacturing.
Innovation Solution
A carrier head design featuring an annular inner and outer ring configuration with independently adjustable pressures, where the outer ring's lower surface is positioned close to the substrate mounting surface to affect pressure on the polishing pad, enhancing polishing uniformity by controlling pressure near the substrate edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single retaining ring is used to hold the substrate, then the structure is simple, but polishing uniformity at the substrate edge is poor
Solution Approach 1:
The single retaining ring is divided into two separate rings: an inner retaining ring that contacts the substrate edge and an outer retaining ring that provides additional support. This segmentation allows independent optimization of each ring's function, with the inner ring controlling substrate positioning and the outer ring enhancing edge support, thereby improving polishing uniformity without excessive complexity
Solution Approach 2:
The inner retaining ring is positioned within the outer retaining ring structure, creating a nested configuration where the inner ring fits inside the outer ring's inner diameter. This nested arrangement maximizes the use of available space, provides multi-layered support for the substrate edge, and improves polishing uniformity while maintaining a compact overall structure
2Manufacturing precision
If the inner ring is made narrow to allow outer ring proximity to substrate edge, then edge pressure control improves, but the inner ring's structural strength decreases
Solution Approach 1:
The narrow inner ring is nested within the outer retaining ring structure, where the outer ring provides additional structural support and rigidity. This nested configuration allows the inner ring to be narrow enough for precise edge pressure control while the outer ring compensates for any strength deficiencies, maintaining both precision and structural integrity
Solution Approach 2:
The structural support functions of both rings are merged to compensate for the narrow inner ring's reduced strength. The outer ring and inner ring work together as a combined support system, where the outer ring's broader structure provides the necessary rigidity while the inner ring maintains precise edge contact for pressure control
3Manufacturing precision
If the outer ring's lower surface is positioned close to the substrate mounting surface, then pressure control on the polishing pad improves, but the risk of contacting the substrate increases
Solution Approach 1:
The outer ring's lower surface is positioned close to the substrate mounting surface only in specific radial zones where it needs to influence polishing pad pressure, while maintaining adequate clearance in other areas to avoid substrate contact. This localized positioning optimizes pressure control effectiveness while minimizing the risk of accidental substrate contact
Solution Approach 2:
The outer ring is positioned close enough to the substrate mounting surface to effectively influence polishing pad pressure distribution, but not so close as to guarantee substrate contact. This partial proximity provides sufficient pressure control benefit while maintaining a safety margin to prevent reliability issues
Data Source
AI summary
A carrier head for a chemical mechanical polisher includes a base, a substrate mounting surface, an annular inner ring and an outer ring. The inner ring has a lower surface configured to contact an upper surface of a substrate positioned on the substrate mounting surface, an outer surface, and an inwardly facing surface extending downwardly from the lower surface and is configured to circumferentially surround the edge of the substrate, the inner ring vertically movable relative to the substrate mounting surface. The outer ring has an inner surface circumferentially surrounding the inner ring, an outer surface, and a lower surface to contact the polishing pad, and the outer ring is vertically movable relative to and independently of the substrate mounting surface and the inner ring.