Polishing Pad with Controlled Air Bubble Diameter Variation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polishing pads struggle to simultaneously achieve both high flatness and surface finish quality in semiconductor wafer polishing, often resulting in scratches or deterioration of flatness due to non-uniform contact and varying air bubble diameters.
Innovation Solution
A polishing pad with a density range of 0.36 to 0.70 g/cm3 and spherical air bubbles with controlled diameter variations, ensuring uniform contact and reduced scratch occurrence, is developed using polyurethane resin foam with adjusted Shore A hardness and air bubble connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hard polishing pad is used to finish the object flat, then flatness is improved, but surface finish deteriorates due to increased scratches
Solution Approach 1:
The polishing pad employs a dual-layer structure where the lower layer (first polishing layer) has higher hardness for flatness, while the upper layer (second polishing layer) has lower hardness and different air bubble characteristics for surface finish. This local differentiation allows each layer to perform its specific function optimally without compromising the other.
Solution Approach 2:
The polishing pad is constructed as a composite of two distinct polyurethane resin foam layers with different density ratios, air bubble characteristics, and hardness levels. This composite structure combines the flatness-enhancing properties of hard foam with the surface-finish-enhancing properties of soft foam, resolving the contradiction between flatness and scratch prevention.
2Object-affected harmful factors
If multi-step polishing is performed to improve surface quality, then surface finish improves, but flatness deteriorates due to trade-off between steps
Solution Approach 1:
The invention merges the functions of multiple polishing steps into a single polishing pad by stacking two layers with complementary characteristics. The first layer addresses flatness while the second layer addresses surface quality, allowing both functions to be performed simultaneously in one step rather than requiring separate sequential steps that trade off against each other.
Solution Approach 2:
The polishing pad is segmented into two functional layers: the first polishing layer optimized for flatness with higher density ratio and different air bubble characteristics, and the second polishing layer optimized for surface quality with lower density ratio and controlled air bubble diameter variation. This segmentation allows independent optimization of each function within a unified structure.
3Ease of operation
If air bubble-based openings are formed on the polishing pad surface, then polishing function is enabled, but non-uniform contact and scratching occur due to irregular air bubble arrangement
Solution Approach 1:
The invention changes the critical parameter of air bubble diameter variation from the conventional large range (1 μm to 5 mm, average 10 μm to 200 μm) to a tightly controlled small range (average 10 μm to 200 μm with standard deviation of 30 μm or less). This parameter control creates more uniform air bubble openings that enable polishing function while reducing contact non-uniformity and scratching.
Data Source
AI summary
A polishing pad is formed from a foam body comprising substantially spherical air bubbles. When the density of a pad constituent material is denoted by DM g/cm3, the density of the polishing pad is in the range of 0.36 to 0.70 DM, the variation (standard deviation σ1) of an opening part diameter based on the air bubbles and formed in the surface of the polishing pad is adjusted to 45 μm or less, when the area of a portion surrounded by opening parts based on the air bubbles formed in the surface of the polishing pad is approximated to a circle, the variation (standard deviation σ2) of a diameter of the circle, is adjusted to 35 μm or less, and the air bubbles included in the foam body may be closed cell or open cell.