Thermoplastic Polyurethane Polishing Pad for Metal Layer Planarization
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Solution Overview
Problem
Conventional polishing pads for semiconductor wafers face challenges in achieving high planarization efficiency and preventing scratches on metal layers, such as copper layers, due to issues with hardness variability and clogging of polishing slurry and dust in non-woven fabric pads, and limitations in controlling the elastic modulus of polyurethane foams.
Innovation Solution
A polishing pad made of thermoplastic polyurethane with specific storage elastic modulus ranges at different temperatures, produced by reacting a high-molecular diol, organic diisocyanate, and a low-molecular chain elongating agent, featuring a non-foaming structure and optimized molecular weight and molar ratios to balance hardness and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional two-pack curable polyurethane is used for polishing pads, then planarization efficiency can be improved by increasing hardness, but scratches on wafer surface increase due to inability to rapidly change elastic modulus with temperature
Solution Approach 1:
The patent applies parameter changes by selecting specific polyurethane materials with controlled elastic modulus values at different temperatures. The elastic modulus at 25°C is controlled at 10-100 MPa for planarization, while at 80°C it drops to 1-50 MPa to prevent scratches. This temperature-dependent parameter change resolves the contradiction between achieving high planarization efficiency and preventing surface damage.
2Productivity
If polishing pad hardness is increased to improve planarization efficiency, then polishing rate improves, but localized hardness on surface causes scratches on metal layers
Solution Approach 1:
The patent applies dynamics by utilizing the temperature-dependent elastic modulus of polyurethane materials. During polishing, the pad surface temperature increases due to friction, causing the elastic modulus to dynamically decrease from 10-100 MPa at 25°C to 1-50 MPa at 80°C. This dynamic softening prevents scratches on metal layers while maintaining polishing rate through the initial higher hardness.
3Strength
If conventional polyurethane foam is used, then wear resistance is improved, but uniform reaction and foaming during production becomes difficult, leading to fluctuation in polishing characteristics
Solution Approach 1:
The patent applies parameter changes by precisely controlling the elastic modulus values within specific ranges (10-100 MPa at 25°C and 1-50 MPa at 80°C) through selection of appropriate polyurethane materials. This parameter control ensures uniform reaction and foaming during production, eliminating fluctuations in polishing characteristics while maintaining wear resistance.
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 pad achieves excellent polishing rate and uniformity while minimizing scratches on semiconductor substrates, with storage elastic modulus tailored to maintain optimal performance across temperature changes.
Implementation Method 1
it is preferable that the elastic modulus of the polishing pad at relatively low temperature be increased to ensure sufficient planarization efficiency, and that if the temperature rises due to excess friction of the polishing pad with the wafer surface, the elastic modulus of the polishing pad decline rapidly so as to prevent the occurrence of scratches on the wafer surface
Data Source
AI summary
Provided are a polishing pad that makes it possible to improve the flatness of the polished surface and planarization efficiency, with fewer scratches, in polishing a metal layer formed on a semiconductor substrate and the like, and a method of polishing a metal layer using the polishing pad. A polishing pad for metal layer wherein the storage elastic modulus at 80°C is 200 to 900 MPa and the storage elastic modulus at 110°C is 40 MPa or less, and a method of polishing a metal layer using the pad.