Thermoset Polyurethane Polishing Pad for Wafer Flatness
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Solution Overview
Problem
Existing polishing pads for semiconductor wafers and other optical materials suffer from tiny undulations on the polished surface, which are difficult to eliminate with current technologies, affecting surface flatness and polishing efficiency.
Innovation Solution
A polishing pad with a thermoset polyurethane foam polishing layer having an in-plane variation in microrubber A hardness of 12 or less, achieved by using a formulation with an isocyanate component and active-hydrogen-containing compounds, including trifunctional and bifunctional polyols, which introduces three-dimensional cross-linking and reduces surface undulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a polishing pad with low microrubber A hardness variation is used, then tiny undulations on the polished surface are decreased, but the formulation complexity increases due to specific polyol requirements
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hydroxyl group value of trifunctional polyols within 150-1,000 mg KOH/g and their content at 10-50 parts by weight per 100 parts of active-hydrogen-containing compounds. This quantitative parameter control transforms the polyurethane foam structure to achieve microrubber A hardness variation of 12 or less, directly resolving the surface flatness issue while providing clear formulation guidelines.
Solution Approach 2:
The patent creates a composite material system combining trifunctional polyols with specific hydroxyl group values, isocyanate components, and other active-hydrogen-containing compounds. This composite formulation approach achieves the desired microrubber A hardness uniformity through synergistic material combinations, where the specific polyol structure interacts with other components to produce the required polishing pad performance.
2Manufacturing precision
If trifunctional polyol with specific hydroxyl group value is used to reduce microrubber A hardness variation, then surface flatness improves, but the manufacturing cost increases
Solution Approach 1:
The patent establishes specific parameter ranges for trifunctional polyols (hydroxyl group value: 150-1,000 mg KOH/g, content: 10-50 parts by weight per 100 parts of active-hydrogen-containing compounds) that optimize both performance and cost. These quantified parameters enable manufacturers to select appropriate polyols within the specified ranges, achieving surface flatness improvement while controlling material costs through defined composition specifications.
3Duration of action of stationary object
If the polishing pad maintains high microrubber A hardness uniformity, then planarization characteristics are maintained over time, but the formulation precision requirements increase
Solution Approach 1:
The patent defines precise parameter ranges for formulation components (trifunctional polyol hydroxyl group value: 150-1,000 mg KOH/g, content: 10-50 parts by weight per 100 parts of active-hydrogen-containing compounds) that ensure microrubber A hardness variation of 12 or less. These controlled parameters create a stable polyurethane foam structure that maintains its polishing performance and planarization characteristics throughout the service life of the polishing pad.
Solution Approach 2:
The patent implements preliminary action by pre-establishing the optimal formulation composition during manufacturing, with specific ratios of trifunctional polyols and other components calculated in advance. This pre-optimized formulation ensures that the polishing pad achieves uniform microrubber A hardness from the beginning, which then maintains stable planarization characteristics throughout its entire service life without requiring adjustments during use.
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
The polishing pad effectively decreases tiny undulations on the polished surface, improving surface flatness and maintaining high planarization characteristics over time, while enhancing polishing rate stability.
Implementation Method 1
the thermoset polyurethane foam contains, as raw material components, an isocyanate component and active-hydrogen-containing compounds
Implementation Method 2
rubbing a wafer against the leather while a polishing agent wherein colloidal silica is contained in an aqueous alkali-based solution is supplied thereonto
Data Source
AI summary
A polishing pad, having a polishing layer comprising a thermoset polyurethane foam, wherein the polishing layer has an in-plane variation of 12 or less in microrubber A hardness, the variation being obtained by measuring the polishing layer from a polishing surface side of the layer, the thermoset polyurethane foam contains, as raw material components, an isocyanate component and active-hydrogen-containing compounds, and the active-hydrogen-containing compounds comprise a trifunctional polyol having at least one terminated hydroxyl group that is a secondary hydroxyl group, and having a hydroxyl group value of 150 to 1,000 mg KOH/g in an amount of 10 to 50 parts by weight for 100 parts by weight of the active-hydrogen-containing compounds.