Humidity-Responsive Polyurethane Polishing Pad for Scratch Reduction
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Solution Overview
Problem
Conventional polishing pads for semiconductor devices exhibit insufficient scratch performance despite high planarization capabilities, particularly when more precise polishing is required.
Innovation Solution
A polishing pad with a polyurethane sheet having a specific range of storage modulus ratios (E'(90%)/E'(30%) and energy loss factor ratios (KEL(90%)/KEL(30%)) is developed, which reduces scratch generation while maintaining a high polishing rate. The polyurethane sheet is manufactured using a method involving a polyurethane bond-containing isocyanate compound and a curing agent, with hollow bodies and controlled humidity exposure to achieve optimal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing pads with high storage modulus are used, then planarization performance is improved, but scratch performance deteriorates
Solution Approach 1:
The patent applies parameter changes by controlling the storage modulus ratio E'(90%)/E'(30%) to be within 0.45-0.65 and energy loss factor ratio KEL(90%)/KEL(30%) to be within 1.8-3.5. This involves changing the physical parameters of the polyurethane sheet through controlled humidity exposure, where the sheet is exposed to high humidity (90% RH) for 24-72 hours before measurement, creating a gradient in mechanical properties that simultaneously achieves planarization and scratch resistance
Solution Approach 2:
The patent applies dynamics by making the polishing pad's mechanical properties adaptable to different humidity conditions. The polyurethane sheet exhibits different storage modulus values at different humidity levels (E' at 30% RH vs E' at 90% RH), allowing the pad to dynamically adjust its hardness during polishing operations. This dynamic property enables the pad to maintain optimal performance across varying environmental conditions while balancing planarization and scratch prevention
2Strength
If polishing pads with high hardness are used, then planarity maintenance is improved, but surface scratch prevention deteriorates
Solution Approach 1:
The patent applies local quality by creating a humidity-dependent gradient in the mechanical properties of the polyurethane sheet. The sheet is exposed to high humidity (90% RH) for 24-72 hours, causing the region near the surface to absorb moisture and soften, while the interior remains relatively harder. This local differentiation allows the surface to be soft enough to prevent scratches while the bulk maintains sufficient hardness for planarity
Solution Approach 2:
The patent applies beforehand cushioning by pre-exposing the polyurethane sheet to high humidity conditions before the actual polishing operation. This pre-conditioning allows the material to absorb moisture and soften in advance, creating a cushioning effect that protects the workpiece surface from scratches during subsequent polishing, while the overall structure maintains enough rigidity for planarization
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 reduces scratch generation while maintaining a high polishing rate, as demonstrated by reduced scratch counts and comparable polishing rates compared to conventional pads, even under high humidity conditions.
Implementation Method 1
The urethane resin foam is normally cured and molded by reacting a prepolymer containing a polyurethane bond-containing isocyanate compound with a curing agent
Implementation Method 2
the storage modulus of a polyurethane sheet under a high humidity condition is sufficiently smaller than the storage modulus of the polyurethane sheet under a low humidity condition
Data Source
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AI summary
To provide a polishing pad and a method for manufacturing the same that are capable of reducing generation of scratches while maintaining a high polishing rate. A polishing pad comprising: a polishing layer having a polyurethane sheet containing substantially spherical cells, wherein E'(90%)/E'(30%) falls within a range of 0.4 to 0.7, where E'(90%) represents a storage modulus of the polyurethane sheet that has been exposed to an environment with a temperature of 23°C and a relative humidity of 90%, as measured in a tension mode at 40°C with an initial load of 148 g, a strain range of 0.1%, and a measurement frequency of 1.6 Hz, and E'(30%) represents a storage modulus of the polyurethane sheet that has been exposed to an environment with a temperature of 23°C and a relative humidity of 30%, as measured in a tension mode at 40°C with an initial load of 148 g, a strain range of 0.1%, and a measurement frequency of 1.6 Hz.