Multi-Lobed CMP Polishing Pad for Uniform Thin-Film Removal
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Solution Overview
Problem
Existing chemical mechanical planarization (CMP) pads lack sufficient polishing performance and uniformity, particularly in removing thin film layers on semiconductor substrates, due to inadequate control of removal rate and material uniformity.
Innovation Solution
A polishing pad with a polymer matrix formed from a reaction product of an isocyanate terminated prepolymer and a curative, incorporating multi-lobed polymeric elements derived from pre-expanded polymeric microspheres, which enhances polishing performance by providing a more consistent and effective polishing action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CMP pads with closed cell polyurethanes are used, then the pad structure is simple and easy to manufacture, but the polishing performance and uniformity are insufficient
Solution Approach 1:
The polishing pad uses a composite structure combining closed-cell polyurethane foam with dispersed polymeric microspheres (5-50 microns in diameter). This composite material approach enhances polishing performance by creating a multi-phase structure that improves slurry retention, maintains consistent contact pressure, and reduces polishing defects while preserving manufacturability through conventional foam formation processes.
Solution Approach 2:
The polymeric microspheres are distributed throughout the polyurethane matrix to create localized regions with different mechanical properties. These micro-inclusions provide localized compliance and slurry reservoirs that improve polishing uniformity across the pad surface without requiring complete structural redesign.
2Productivity
If higher removal rates are achieved, then productivity increases, but uniformity of removal and defect generation worsen
Solution Approach 1:
The incorporation of polymeric microspheres modifies the mechanical parameters of the polishing pad, including compressibility, elasticity, and surface compliance. These parameter changes enable the pad to maintain consistent contact pressure during polishing, improving removal uniformity while allowing for effective material removal rates.
Solution Approach 2:
The microsphere-containing structure provides inherent feedback mechanisms where the compressible microspheres adjust to local variations in substrate topography and pad wear, automatically compensating for pressure non-uniformities and maintaining consistent polishing performance throughout the process.
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 demonstrates improved removal rates and reduced defects such as scratches and chatter-marks on substrates, achieving better planarization and uniformity in CMP processes.
Implementation Method 1
a polymer matrix that is the reaction product of an isocyanate terminated prepolymer with a curative
Implementation Method 2
preparing a pre-blend of the isocyanate terminated prepolymer and the pre-expanded fluid filled polymeric microspheres in a stirred tank
Implementation Method 3
The shear and any slurry particles trapped at the pad/wafer junction abrade the substrate surface, leading to removal of material from the substrate
Data Source
AI summary
A polishing pad for chemical mechanical polishing comprises a polishing layer that comprises a polymer matrix that is the reaction product of an isocyanate terminated prepolymer with a curative, wherein the polymer matrix has hard segments and soft segments wherein multi-lobed polymeric elements formed from pre-expanded polymeric microspheres are present in the polymer matrix. The polishing pad can be made by preparing a pre-blend of the isocyanate terminated prepolymer and the pre-expanded fluid filled polymeric microspheres in a stirred tank; pumping a portion of the pre-blend from a bottom of the stirred tank through a conduit and recycling to a top region of the stirred tank, mixing a portion of the pre-blend with the curative to form a mixture, casting the mixture in a mold, curing the mixture in the mold.