Polishing Pad With Trapezoidal Grooves For Wafer Flatness
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Solution Overview
Problem
The existing wafer polishing processes face challenges with reduced flatness and degradation in localized light scattering (LLS) quality due to excessive surface tension and impurities during the polishing of large wafers, particularly with traditional polishing pads that undergo hot press processing or cutting, leading to thermal deformation and rough surfaces.
Innovation Solution
A polishing pad with trapezoidal-shaped grid grooves, where the entrance area is smaller than the bottom area, is used, combined with a porous nap layer and non-woven fabric layer, and film-coated surfaces to ensure smooth slurry flow and minimize surface tension, preventing impurity discharge and maintaining wafer flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If hot press processing is used to form grooves in the polishing pad, then grooves are formed to reduce surface tension, but the contact surface is thermally deformed and hardened, causing stress concentration and reduced wafer flatness
Solution Approach 1:
The patent replaces the thermal field (hot press processing) with a mechanical field (cold press processing) to form grooves in the polishing pad. This substitution avoids thermal deformation and hardening of the contact surface, preventing stress concentration that would otherwise reduce wafer flatness, while still achieving the groove formation needed to reduce surface tension.
Solution Approach 2:
The patent changes the temperature parameter from high (hot press) to low or room temperature (cold press) during groove formation. This parameter change eliminates thermal effects that cause surface deformation and hardening, thereby preventing the subsequent stress concentration and wafer flatness degradation while maintaining the functional benefit of groove formation.
2Object-affected harmful factors
If cutting processing is used to form grooves in the polishing pad, then grooves are formed to reduce surface tension, but the cut surface is rough and impurities remain in the grooves, leading to degradation in localized light scattering quality
Solution Approach 1:
The patent replaces the cutting mechanical system with a pressing mechanical system to form grooves. This substitution eliminates the rough cut surfaces and impurity generation associated with cutting, while still achieving effective groove formation through compression, thereby preserving localized light scattering quality.
3Reliability
If a porous polishing pad is used for final polishing, then the pad structure supports the wafer, but surface tension increases with wafer size, making it difficult to separate the wafer from the pad after polishing
Solution Approach 1:
The patent segments the polishing pad surface by forming a grid pattern of grooves. This segmentation creates multiple small channels that disrupt the continuous surface tension field, allowing the wafer to be easily separated from the pad after polishing while the pad maintains its supportive function during the polishing process.
Solution Approach 2:
The patent extracts material from the polishing pad surface to form grooves, creating voids that reduce the effective contact area between the pad and wafer. This extraction reduces surface tension and facilitates wafer separation while preserving the pad's structural support capability.
Data Source
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AI summary
The present invention provides a polishing pad for a wafer polishing apparatus, comprising: an upper pad having a front surface part, which has a cut surface and is in contact with a wafer, a rear surface part positioned on the lower part of the front surface part, and a plurality of grid grooves passing through the front surface part and the rear surface part; a lower pad, which is arranged on the lower part of the upper pad and can be attached to a surface plate; and an adhesion part positioned between the upper pad and the lower pad to couple the upper pad with the lower pad.