Dynamic Retainer Ring Convex Blocks for Wafer Polishing Uniformity
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Solution Overview
Problem
Conventional semiconductor polishing apparatuses experience overpolishing at the outer peripheral edge due to radial gaps between the retainer ring and the wafer, leading to uneven polishing and potential separation of insulation films, which affects the yield of semiconductor devices.
Innovation Solution
The polishing apparatus adjusts the inner diameter of the retainer ring by moving convex blocks radially inward and outward in response to the rotation of the polishing head, eliminating the radial gap and ensuring uniform polishing pressure across the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a retainer ring is used to suppress wafer deviation, then wafer positioning stability is improved, but a radial gap between the retainer ring and wafer causes rebound of the polishing pad leading to overpolishing at the outer peripheral edge
Solution Approach 1:
The retainer ring is designed with movable convex blocks that can dynamically adjust their radial position. During wafer loading, the blocks are in a retracted state to allow easy placement. During polishing, the blocks move radially outward to contact the wafer and eliminate the radial gap, preventing pad rebound while maintaining positioning stability.
Solution Approach 2:
The inner diameter of the retainer ring is made variable through the movable convex blocks. The block position can be adjusted between a retracted state (larger effective inner diameter for easy loading) and an extended state (smaller effective inner diameter to eliminate radial gap). This parameter change allows the system to optimize for different operational phases.
2Productivity
If the wafer is shifted toward the downstream side during rotation, then polishing proceeds continuously, but variation in polishing amount in the circumferential direction increases
Solution Approach 1:
The movable convex blocks dynamically adjust during the polishing process. As the wafer rotates and shifts downstream, the blocks maintain continuous contact with the wafer surface, compensating for the shift and ensuring uniform polishing pressure is applied throughout the circumferential direction, thereby reducing variation in polishing amount.
Data Source
AI summary
A polishing apparatus according to an embodiment includes a first polishing part, a second polishing part, and an annular part. The second polishing part includes a mounting surface for a semiconductor substrate, and rubs the semiconductor substrate mounted on the mounting surface while pressing the semiconductor substrate against the first polishing part. The annular part includes a support part provided in the second polishing part, and a plurality of convex portions that project from the support part toward the first polishing part, are arranged in a circumferential direction around the mounting surface while being supported by the support part, and are movable in a radial direction of the semiconductor substrate.