Retainer Ring Wear Compensation for CMP Uniformity
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Solution Overview
Problem
The existing retainer rings in CMP apparatuses for semiconductor wafer polishing suffer from non-uniform polishing due to wear, leading to increased effective pressure near the edge of the wafer, which exacerbates surface uniformity issues and requires continuous pressure adjustments or frequent replacements, hindering productivity.
Innovation Solution
The retainer ring is designed with a shape that increases its contact area with the polishing pad as it wears, using a combination of grooves and concentric grooves of varying depths to maintain consistent pressure and prevent non-uniform polishing, thereby stabilizing the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retainer ring is used to hold the semiconductor wafer during CMP polishing, then the wafer can be securely positioned and polishing can be performed, but the retainer ring wears down over time causing non-uniform polishing and requiring frequent replacement
Solution Approach 1:
The retainer ring is pre-formed with a wear compensation shape that anticipates future wear. The contact surface is designed with a specific profile (convex, concave, or stepped) that will automatically compensate for wear as the ring is used, maintaining uniform polishing pressure throughout the ring's service life without requiring replacement
Solution Approach 2:
The contact surface geometry of the retainer ring is deliberately designed with non-uniform thickness or profile variations. As the ring wears, these pre-designed geometric parameters change in a controlled manner to maintain consistent contact pressure with the polishing pad, compensating for material loss
2Productivity
If the retainer ring contact pressure is increased to improve polishing efficiency, then polishing rate increases, but edge effects and non-uniform polishing are exacerbated
Solution Approach 1:
Different regions of the retainer ring contact surface are designed with different geometries to achieve locally optimized pressure distribution. The contact surface may have convex portions, concave portions, or stepped structures that create varying local contact areas, ensuring uniform pressure distribution across the wafer surface while maintaining high overall polishing efficiency
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively stabilizes the within-wafer uniformity by automatically adjusting the contact area with the polishing pad, reducing variations in polishing characteristics and maintaining high planarization quality throughout the polishing process without the need for continuous pressure adjustments.
Implementation Method 1
the retainer ring is increasingly worn. The resin material most typically used for retainer ring 1 is PPS (polyphenylene sulfide), and retainer ring 1 made of PPS is worn down by approximately 0.1 mm to 0.5 mm after 1000 wafers are polished
Implementation Method 2
CMP apparatuses are generally used to directly polish the surface of semiconductor devices... The surface of the wafer is polished in this basic operation
Data Source
AI summary
A semiconductor device manufacturing apparatus according to the present invention comprises a head for holding a semiconductor wafer, a retainer ring for surrounding the outer periphery of the semiconductor wafer held by the head, and a polishing pad for polishing a polished surface of the semiconductor wafer. This apparatus presses the polished surface of the semiconductor wafer against the polishing pad together with the retainer ring to polish the semiconductor wafer. The retainer ring used in the present invention has a surface that is in contact with the polishing pad, which increases a contact area of the retainer ring against the polishing pad in accordance with wear of the retainer ring.