Open Lattice Polishing Pad for CMP Defect Reduction
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads have suboptimal contact mechanics and fluid mechanics due to irregular surface textures, leading to high defect formation and inefficient planarization, with a need for frequent conditioning and compromised performance between defectivity and planarization efficiency.
Innovation Solution
A polishing pad with an open lattice structure of interconnected polymeric filaments, providing a high surface area to volume ratio and self-renewing properties, which maintains a consistent contact area and improves fluid flow, eliminating the need for conventional conditioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing pads with irregular surface textures are used, then polishing process can be performed, but contact mechanics and fluid mechanics are suboptimal leading to high defect formation and inefficient planarization
Solution Approach 1:
The polishing pad is segmented into multiple discrete filaments arranged in layers, creating a lattice structure. This segmentation provides controlled contact points while maintaining fluid flow pathways, resolving the contradiction between achieving good contact mechanics and preventing defect formation.
Solution Approach 2:
Different regions of the polishing pad have different properties - the filament structure provides localized compliance at contact points while maintaining overall structural integrity. This local quality variation allows optimal contact at the wafer interface while maintaining pad stability, reducing defects.
2Reliability
If frequent conditioning is performed to maintain polishing surface, then polishing rate and uniformity are maintained, but productivity is reduced due to intermittent polishing pauses
Solution Approach 1:
The lattice structure of filaments is self-renewing through controlled wear mechanisms. As filaments wear, the structure naturally maintains its geometry without requiring external conditioning intervention, allowing continuous polishing operation and eliminating productivity loss from conditioning pauses.
Solution Approach 2:
The pad structure is pre-configured with a lattice of filaments that anticipates wear patterns. This preliminary structural design ensures that even as wear occurs, the geometry is maintained without needing reactive conditioning, enabling uninterrupted polishing.
3Productivity
If polishing pad surface glazes over time, then polishing rate decreases and uniformity is compromised, but frequent conditioning increases process complexity and time
Solution Approach 1:
The filament lattice structure resists glazing through its geometric design. The open structure allows slurry penetration and debris evacuation, preventing the buildup that causes glazing. This self-maintaining property eliminates the need for complex conditioning systems while sustaining high polishing rates.
Solution Approach 2:
The lattice structure creates inherent porosity and open pathways for slurry flow. This porous architecture prevents slurry stagnation and debris accumulation at the surface, eliminating glazing without requiring conditioning intervention, thus maintaining productivity and reducing complexity.
4Manufacturing precision
If conventional polishing pads are used, then polishing can be performed, but real contact area is limited and slurry flow is restricted leading to inefficient debris removal
Solution Approach 1:
The segmented filament structure creates multiple discrete contact regions distributed across the pad surface. This segmentation increases the effective real contact area while simultaneously creating channels for slurry flow between filaments, resolving the contradiction between contact area and fluid flow efficiency.
Solution Approach 2:
The lattice structure provides locally optimized properties - dense filament regions for contact and open channels for fluid flow. This spatial variation in local quality allows simultaneous achievement of high contact area uniformity and efficient slurry/debris transport.
Data Source
AI summary
The polishing pad (104) is useful for polishing at least one of a magnetic, optical and semiconductor substrate (112) in the presence of a polishing medium (120). The polishing pad 104 includes multiple layers of polishing filaments (200, 300, 400, 500) stacked on a base layer (204, 404, 504) of polishing filaments, the multiple layers of polishing filaments (200, 300, 400, 500) having a sequential stacked formation with each layer of the polishing filaments being above and attached to a lower polishing filament, the multiple layers of polishing filaments (200, 300, 400, 500) being parallel to a polishing surface of the polishing pad (104) and wherein individual polishing filaments (202, 302, 402) of the multiple layers of polishing filaments (200, 300, 400, 500) are above an average of at least three polishing filaments (202, 302, 402), to form the polishing pad having an open lattice structure of interconnected polishing filaments (210, 310, 410, 510, 610).