CMP Polishing Pad Window with UV-Transparent Polyurethane
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Solution Overview
Problem
Current polishing pad windows for chemical mechanical polishing lack adequate transmission in the ultraviolet region, particularly between 250-380 nm, which is necessary for accurate endpoint detection in semiconductor processing.
Innovation Solution
A polishing pad with a transparent window made from a polyurethane composition formed by reacting a polymeric polyol, a polyisocyanate, and a curing agent in the presence of a hard segment inhibitor, resulting in an amorphous mixture with improved light transmissivity across the desired wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional window materials are used in polishing pads, then the polishing pad structure is simple and easy to manufacture, but the light transmission in the ultraviolet region (250-380 nm) is insufficient for accurate endpoint detection
Solution Approach 1:
The patent changes the chemical composition parameters of the window material by using a polyurethane system with specific ratios of polyol, polyisocyanate, and curing agent, and by controlling the molecular weight and structure of the polymeric components to achieve optimal UV transmission while maintaining mechanical properties
Solution Approach 2:
The patent employs a composite polyurethane material system combining multiple components (polymeric polyol, polyisocyanate, curing agent, and optional additives) to create a window that simultaneously achieves high UV transmission and appropriate mechanical properties for polishing pad application
2Measurement precision
If the window material is made more transparent in the UV region, then endpoint detection at lower wavelengths is improved, but the mechanical properties (strength, hardness) of the window may deteriorate
Solution Approach 1:
The patent optimizes the molecular weight, structure, and composition ratios of the polyurethane components to achieve a balance where the material remains mechanically strong while transmitting UV light effectively. Specific attention is given to selecting polyols and polyisocyanates with appropriate molecular weights and structures
Solution Approach 2:
The patent uses a composite polyurethane system where the combination of specific components creates synergistic effects that simultaneously provide mechanical strength and UV transparency. The curing agent and optional additives are selected to enhance both optical and mechanical properties
3Difficulty of detecting and measuring
If a transparent window is inserted in the polishing pad to enable optical detection, then endpoint detection is facilitated, but the device complexity increases
Solution Approach 1:
The patent merges the window function directly into the polishing pad structure by integrating the transparent polyurethane window as an integral part of the pad, eliminating the need for separate window components and reducing overall device complexity
Solution Approach 2:
The polyurethane window material serves multiple functions simultaneously: it provides UV transparency for detection, maintains mechanical properties for structural integrity, and can be integrated directly into the polishing pad fabric, making it a multi-functional component
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 polyurethane window achieves good light transmissivity at 250 nm and combined with a low modulus, enables the use of broad-spectrum light source detectors for endpoint detection, while maintaining mechanical properties similar to the polishing pad material.
Implementation Method 1
the window comprises a polyurethane composition formed by reacting, in the presence of a hard segment inhibitor, a polymeric polyol, a polyisocyanate, and a curing agent... the polyurethane composition is free of carbon-carbon double bonds... achieves good light transmissivity at 250 nm
Data Source
AI summary
The polishing pad is useful in chemical mechanical polishing. The polishing pad includes a polishing portion having a top polishing surface and a polishing material. There is an opening through the polishing pad and a transparent window within the opening. The transparent window is secured to the polishing pad. The window includes a polyurethane composition formed by reacting, in the presence of a hard segment inhibitor for reducing size of hard segment domains, a polymeric polyol, a polyisocyanate and a curing agent. The curing agent includes three or more hydroxyl groups forming hard segments and the polyurethane composition is an amorphous mixture of hard segments in a soft segments matrix and is free of carbon-carbon double bonds.