CMP Pad Constant Area Spiral Grooves for Uniform Polishing
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads lack effective groove patterns that ensure uniform slurry distribution and material removal, leading to non-uniform polishing and potential wafer tilt due to variations in hydrodynamic states between the pad and wafer.
Innovation Solution
A CMP pad with overlaid constant area spiral grooves, where each groove set is designed using specific equations to maintain a consistent circumference fraction across the pad, ensuring uniform slurry film thickness and balanced forces parallel to the pad's mean plane, thereby improving polishing uniformity and material removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional groove patterns are used on CMP pads, then manufacturing is simpler, but polishing uniformity deteriorates due to non-uniform slurry distribution and hydrodynamic variations
Solution Approach 1:
The polishing pad surface is segmented into multiple groove patterns including radial grooves, concentric circular grooves, Cartesian grid grooves, and spiral grooves. Each groove type segments the slurry flow path differently to ensure uniform distribution across the polishing surface, resolving the contradiction by using segmented patterns rather than simple single-pattern grooves
Solution Approach 2:
The invention transitions from two-dimensional groove patterns to three-dimensional groove structures with varying depths. The groove depth varies as a function of radial distance from the center, creating a depth dimension that compensates for hydrodynamic variations and maintains uniform polishing pressure, thereby improving polishing uniformity without excessive complexity
2Manufacturing precision
If groove width and depth are made uniform across all grooves, then manufacturing is easier, but slurry distribution uniformity deteriorates due to hydrodynamic variations
Solution Approach 1:
The groove depth is made location-dependent, varying as a function of radial distance from the pad center. Grooves near the center have different depths than grooves at the periphery, creating local quality variations that compensate for hydrodynamic effects and ensure uniform slurry distribution, while maintaining relatively simple fabrication methods
Solution Approach 2:
The groove depth parameter is changed as a function of radial position, transitioning from uniform depth to variable depth. This parameter change allows the groove pattern to adapt to hydrodynamic variations across the polishing surface, improving slurry distribution uniformity without requiring complex manufacturing processes
3Productivity
If groove patterns are simplified, then device complexity is reduced, but polishing performance deteriorates due to non-uniform material removal
Solution Approach 1:
Multiple groove patterns (radial, concentric circular, Cartesian grid, and spiral grooves) are merged into a single integrated groove pattern on the polishing pad. This combination leverages the advantages of each pattern type to achieve uniform material removal across the wafer surface, resolving the contradiction by combining rather than simplifying the groove structures
Data Source
AI summary
A circular chemical mechanical polishing pad that includes a polishing surface having a concentrically located origin. The polishing surface includes groove sets each containing grooves arranged in a pattern in which ones of the grooves in one groove set cross ones of the grooves in another set. The grooves in each groove set are configured and arranged so that the fraction of the polishing surface that is grooved, as measured along any circle that is concentric with the origin and crosses the grooves, is substantially constant, i.e., within about 25% of its average.