CMP Pad Casting Method with Controlled Microsphere Expansion
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Solution Overview
Problem
Commercial polyurethane polishing pads for semiconductor fabrication are sensitive to diamond conditioning, leading to variations in polishing removal rates and efficiency, particularly during interlayer dielectric polishing with fumed silica slurry, as the diamond conditioner wears down, resulting in reduced performance over time.
Innovation Solution
A method involving a polishing pad manufactured with a liquid polyurethane material containing a blend of preexpanded and unexpanded fluid-filled polymeric microspheres, where the microspheres expand at specific temperatures to form a polyurethane matrix with controlled pore size and reduced sensitivity to conditioner wear, achieved by heating the microspheres to a temperature that increases their diameter without gas escape, resulting in a pad with improved removal rates and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If commercial polyurethane polishing pads are used with diamond conditioning, then polishing removal rate is maintained initially, but sensitivity to conditioner wear increases over time, leading to performance variation
Solution Approach 1:
The patent changes the physical and chemical parameters of the polishing pad by incorporating fluid-filled polymeric microspheres with specific transition temperatures. These microspheres undergo controlled expansion during curing to create an optimized pore structure that reduces sensitivity to diamond conditioner wear, thereby maintaining consistent removal rates throughout pad life
Solution Approach 2:
The patent creates a composite polishing pad structure by combining polyurethane material with fluid-filled polymeric microspheres. This composite structure provides both the mechanical properties needed for polishing and the controlled pore architecture that reduces conditioner sensitivity, achieving both high productivity and reliability
2Ease of manufacture
If polyurethane is cast into cakes and cut into thin polishing pads, then manufacturing efficiency is improved, but the pads exhibit sensitivity to diamond conditioning and performance variation
Solution Approach 1:
The patent modifies the casting process by controlling the temperature parameters during curing. By heating the liquid polyurethane material to specific temperatures below the microsphere expansion temperature, the microspheres expand uniformly within the curing matrix, creating consistent pore structures that ensure uniform polishing properties across all pads manufactured this way
3Productivity
If in-situ conditioning with diamond disks is used, then polishing pad surface is roughened to maintain removal rate, but conditioner wear leads to shallower channels and reduced removal rate over time
Solution Approach 1:
The patent creates a porous polishing pad structure through the controlled expansion of fluid-filled microspheres during curing. This pre-formed porous architecture provides optimal channels for slurry penetration and abrasive action, reducing dependence on diamond conditioner wear and maintaining consistent removal rates throughout the pad's operational life
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 resulting polishing pads exhibit higher removal rates, better within-wafer uniformity, and reduced sensitivity to conditioning process variations, maintaining performance stability over the life of the pad.
Implementation Method 1
heating the blend of preexpanded and unexpanded fluid-filled polymeric microspheres in the liquid polyurethane material to a temperature of at least Tstart of the unexpanded fluid-filled polymeric microspheres to increase the diameter of the unexpanded fluid-filled polymeric microspheres
Implementation Method 2
obtaining a liquid polyurethane material formed from an isocyanate-terminated molecule and a curative agent
Data Source
AI summary
The invention provides a method of manufacturing a polishing pad suitable for planarizing at least one of semiconductor, optical and magnetic substrates. The method obtains a liquid polyurethane material formed from an isocyanate-terminated molecule and a curative agent. The liquid polyurethane material has a Tgel temperature and contains fluid-filled polymeric microspheres. The fluid-filled polymeric microspheres are a blend of preexpanded and unexpanded fluid-filled polymeric microspheres. The preexpanded and unexpanded fluid-filled polymeric microspheres each have a Tstart temperature where diameter of the preexpanded and unexpanded fluid-filled polymeric microspheres increases and a Tmax temperature where gas escapes to decrease diameter of the expanded and unexpanded fluid-filled polymeric microspheres. The cured polyurethane matrix contains preexpanded and expanded fluid-filled polymeric microspheres.