CMP Pad Light Stable Polymeric Endpoint Detection Window
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Solution Overview
Problem
Conventional polymeric endpoint detection windows in chemical mechanical polishing (CMP) systems degrade when exposed to light wavelengths below 400 nm, leading to undesirable deformation and lack of durability, which is a challenge in advanced semiconductor polishing applications requiring precise endpoint detection.
Innovation Solution
A CMP pad with a light stable polymeric endpoint detection window made from a polyurethane reaction product of an aromatic polyamine and an isocyanate terminated prepolymer polyol, combined with a light stabilizer, having a stoichiometric ratio of amine moieties to unreacted NCO moieties less than 95%, which exhibits low strain and high optical transmission even under exposure to UV light, ensuring durability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymeric endpoint detection windows are used in CMP systems, then the windows provide initial optical transmission capability, but they degrade and deform when exposed to UV light wavelengths below 400 nm, leading to lack of durability
Solution Approach 1:
The patent changes the chemical composition parameters of the polymeric window material by incorporating specific UV stabilizers and adjusting the polymer matrix formulation. This allows the window to maintain its optical transmission properties and structural integrity when exposed to UV light wavelengths below 400 nm, directly resolving the degradation and deformation issues of conventional polymers.
Solution Approach 2:
The patent creates a composite polymeric material by combining base polymer components with UV stabilizing agents and potentially other functional additives. This composite structure provides both the necessary optical transmission characteristics and enhanced UV resistance, solving the contradiction between initial optical performance and long-term durability under UV exposure.
2Stability of the object's composition
If filters are used to attenuate UV light before exposure to the endpoint detection window, then the window material stability is improved, but the complexity of the optical system increases and light transmission efficiency decreases
Solution Approach 1:
The patent merges the UV protection function directly into the endpoint detection window material itself by incorporating UV stabilizers within the polymer matrix. This eliminates the need for separate external filters in the optical path, thereby reducing system complexity while maintaining both window stability and light transmission efficiency.
Solution Approach 2:
The UV stabilizer components act as intermediary substances within the polymeric window material that absorb or dissipate UV energy before it can damage the window structure. These intermediaries protect the window internally without requiring external filtering components, simplifying the overall optical system.
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 provides a CMP pad with a creep-resistant and clear window that maintains optical transmission and dimensional stability, enabling effective endpoint detection in CMP processes, especially for advanced semiconductor applications like copper-barrier and shallow trench isolation, without significant degradation from UV exposure.
Implementation Method 1
a light stable polymeric endpoint detection window... having a stoichiometric ratio of amine moieties to unreacted —NCO moiety groups less than 95:100, which exhibits low strain and high optical transmission
Implementation Method 2
Conventional polymer based endpoint detection windows often exhibit undesirable degradation upon exposure to light having a wavelength of 330 to 425 nm... a light stabilizer component comprising at least one of a UV absorber and a hindered amine light stabilizer
Data Source
AI summary
A chemical mechanical polishing pad is provided, comprising: a polishing layer having a polishing surface; and, a light stable polymeric endpoint detection window, comprising: a polyurethane reaction product of an aromatic polyamine containing amine moieties and an isocyanate terminated prepolymer polyol containing unreacted —NCO moieties; and, a light stabilizer component comprising at least one of a UV absorber and a hindered amine light stabilizer; wherein the aromatic polyamine and the isocyanate terminated prepolymer polyol are provided at an amine moiety to unreacted —NCO moiety stoichiometric ratio of <95%; wherein the light stable polymeric endpoint detection window exhibits a time dependent strain of ≦0.02% when measured with a constant axial tensile load of 1 kPa at a constant temperature of 60° C. at 100 minutes and an optical double pass transmission of ≧15% at a wavelength of 380 nm for a window thickness of 1.3 mm; and, wherein the polishing surface is adapted for polishing a substrate selected from a magnetic substrate, an optical substrate and a semiconductor substrate. Also provided is a method of polishing a substrate (preferably a semiconductor wafer) using the chemical mechanical polishing pad provided.