Fixed Abrasive Pad With Gradient Density Sub-Layers
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Solution Overview
Problem
The fixed abrasive polishing method faces challenges with unstable polishing performance due to the continuous consumption and damage of abrasive blocks, leading to decreased removal rates and increased scratches, which affects the quality and stability of the polishing process.
Innovation Solution
A fixed abrasive pad with multiple abrasive sub-layers, where the abrasive density increases layer-by-layer from the top to the bottom, and the sub-layers are patterned to form discrete blocks with a uniform distribution, ensuring a stable polishing process by matching the increasing density with the decreasing surface area of the abrasive blocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed abrasive blocks are used on the polishing pad, then polishing precision and control over surface topography are improved, but the abrasive blocks are continuously consumed and damaged, leading to unstable polishing performance
Solution Approach 1:
The abrasive layer is segmented into multiple sub-layers (first sub-layer, second sub-layer, third sub-layer, etc.), each with different abrasive densities. This segmentation allows different regions of the abrasive layer to serve different functions during the polishing process, maintaining performance stability as the pad wears.
Solution Approach 2:
Different sub-layers of the abrasive pad are assigned different local qualities in terms of abrasive density. The first sub-layer has lower abrasive density for initial polishing, while subsequent sub-layers have progressively higher densities to maintain effectiveness as the pad consumes. This local differentiation ensures stable polishing performance throughout the pad's working life.
2Ease of manufacture
If abrasive density is uniformly distributed in the polishing pad, then manufacturing is simpler, but the contact surface area decreases as abrasive blocks are consumed, reducing removal rates
Solution Approach 1:
The abrasive density parameter is changed progressively across different sub-layers of the polishing pad. The first sub-layer has a first abrasive density, the second sub-layer has a second abrasive density higher than the first, and the third sub-layer has a third abrasive density higher than the second. This parameter progression compensates for the decreasing contact surface area as the pad wears, maintaining removal rates throughout the pad's working life.
3Productivity
If higher polishing speed is used to compensate for smaller contact surface area, then removal rates are maintained, but the over polish window is enlarged, increasing the risk of erosions and dishing
Solution Approach 1:
Instead of increasing polishing speed to maintain removal rates, the invention changes the abrasive density parameter across different sub-layers. This allows the system to maintain effective polishing action without requiring higher speeds, thereby preserving a narrow over polish window and avoiding erosions and dishing while sustaining productivity.
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 stabilizes the polishing process, improves removal rates, and extends the working life of the polishing pad by maintaining high efficiency and accuracy, reducing scratches and the need for frequent replacements.
Implementation Method 1
The abrasive density of the abrasive sub-layers increases layer-by-layer from the top abrasive sub-layer to a bottom abrasive sub-layer... only the projections (referred as abrasive blocks herein) attached on the polishing pad 102 have contact with the surface of the wafer 103, so that a contact surface area between the polishing slurry and the wafer is smaller than a contact surface area in the conventional free abrasive polishing method
Data Source
AI summary
A fixed abrasive pad includes a substrate and a plurality of discrete abrasive blocks attached thereon, wherein the abrasive blocks comprise a plurality of abrasive sub-layers, wherein the abrasive density of the sub-layers increases layer-by-layer from the top sub-layer to the bottom sub-layer according to a predetermined ratio. The predetermined ratio ranges from about 1.099 to about 1.124.