Polyurethane Polishing Pad Viscoelastic Stability
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Solution Overview
Problem
Polishing pads used in CMP processing exhibit significant variation in polishing rate across different workpieces and over time, leading to instability in polishing performance.
Innovation Solution
A polishing pad with a polyurethane sheet that maintains a low rate of change in tan δ peak value and storage elastic modulus between dry and wet states, achieved through specific manufacturing conditions and material composition, including the use of 2,6-tolylene diisocyanate and 3,3′-dichloro-4,4′-diaminodiphenylmethane, to ensure consistent polishing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional urethane resin foam polishing pads are used with standard curing agents, then the polishing pad can be manufactured with basic porosity and hardness, but the polishing rate shows great variation across multiple workpieces and over time
Solution Approach 1:
The invention changes the chemical parameter of the curing agent from conventional options (polypropylene glycol, polyethylene glycol) to a polyamide compound with specific molecular weight (1000-3000). This parameter change in the curing agent fundamentally alters the crosslinking density and network structure of the polyurethane foam, resulting in stable tan δ peak values and consistent polishing rates across multiple workpieces.
Solution Approach 2:
The invention creates a composite polyurethane system by combining specific prepolymer components (polyol with MW 500-2000, diisocyanate) with the key curing agent (polyamide compound with MW 1000-3000). This composite material approach produces a foam structure with optimized cell morphology and stable viscoelastic properties, achieving both porosity for slurry retention and structural stability for consistent polishing performance.
2Quantity of substance
If the polishing pad structure is optimized for porosity to hold slurry, then polishing can proceed effectively, but the structural integrity and flatness maintenance become compromised
Solution Approach 1:
The invention utilizes a porous polyurethane foam structure formed through controlled cell expansion during curing. The use of polyamide curing agent creates a balanced cell structure with adequate porosity for slurry penetration and retention, while maintaining sufficient wall strength to preserve pad flatness and structural integrity during polishing operations.
Solution Approach 2:
The invention achieves different local properties within the foam structure: the cell walls provide structural strength and flatness maintenance, while the cell interiors and interstitial spaces provide porosity for slurry holding. The polyamide curing agent enables this spatial differentiation of properties throughout the foam matrix.
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 solution results in a polishing pad with high stability and consistency of polishing rate over time, improved responsiveness to polishing pressure, and enhanced polishing performance, as demonstrated by reduced variation in polishing rates across multiple workpieces.
Implementation Method 1
The urethane resin foam is usually formed by a curing reaction of a prepolymer containing a polyurethane bond-containing isocyanate compound with a curing agent (dry method)
Implementation Method 2
a rate of change in a tan δ peak value... between a loss tangent tan δ peak value... in a wet state... and a loss tangent tan δ peak value... in a dry state... is 15% or less
Data Source
AI summary
A polishing pad is equipped with a polishing layer having a polyurethane sheet, wherein a tan δ peak value change rate determined by formula: tan δ peak value change rate=|tan δ peakwet−tan δ peakdry|/tan δ peakdry×100, is not more than 15%, where tan δ peakwet represents the peak value of the loss tangent tan δ, of the polyurethane sheet in a wet state after being immersed in water for three days, within a temperature range of 20-100° C. in a tensile mode under an initial load of 148 g with a strain range of 0.1% at a measurement frequency of 1.6 Hz, and tan δ peakdry represents the peak value of the loss tangent tan δ, of the polyurethane sheet in a dry state without being immersed in water, within a temperature range of 20-100° C. in a tensile mode under an initial load of 148 g with a strain range of 0.1% at a measurement frequency of 1.6 Hz.