Polishing Pad Window Support Spacer for Optical Monitoring
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Solution Overview
Problem
In chemical mechanical polishing (CMP) processes, the deformation of the polishing pad's window at high temperatures leads to recess formation, causing slurry accumulation and light scattering, which degrades the accuracy of optical monitoring systems used for endpoint detection.
Innovation Solution
A solid light-transmissive window in the polishing pad is supported by a spacer positioned on the optical fiber, reducing sagging and slurry accumulation, thereby enhancing the reliability and accuracy of optical monitoring systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the polishing pad window is made light-transmissive for optical monitoring, then endpoint detection capability is improved, but window deformation and slurry accumulation occur at high temperatures
Solution Approach 1:
The patent introduces an intermediary support structure (spacer or collar) positioned between the window and the polishing pad backing layer. This intermediary element prevents direct contact that would cause deformation while allowing the window to maintain its light-transmissive function. The spacer acts as a mediator that separates the optical component from the mechanical structure, eliminating the deformation problem while preserving endpoint detection capability.
Solution Approach 2:
The patent addresses the window deformation problem by adding a dimensional element - a spacer or collar extending in the vertical dimension between the window and the backing layer. This vertical spacing creates a gap that prevents thermal deformation from propagating to the window, thereby maintaining optical path integrity while preserving the light-transmissive function for endpoint detection.
2Stability of the object's composition
If the window is supported closer to the optical fiber to reduce deformation, then window stability is improved, but the optical path may be blocked
Solution Approach 1:
The support structure is designed as a segmented annular spacer or collar with a central aperture. This segmentation allows the support element to provide stability to the window while the central aperture ensures the optical path remains unobstructed. The segmented design enables the spacer to fulfill dual functions: mechanical support and optical transparency.
Solution Approach 2:
The spacer or collar is positioned locally around the periphery of the window rather than covering the entire window area. This localized support provides stability where needed (at the edges) while leaving the central optical path clear. The local quality approach ensures window stability without compromising illumination intensity in the critical optical transmission region.
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 improves the signal intensity and reliability of optical monitoring systems by preventing slurry accumulation and maintaining the integrity of the optical path, ensuring accurate endpoint detection during CMP processes.
Implementation Method 1
an optical fiber having an end, and a spacer having a vertical aperture therethrough. A bottom surface of the spacer contacts the end of the optical fiber
Implementation Method 2
an optical monitoring system for in-situ measuring of uniformity of a layer on a substrate during polishing of the layer has been employed. The optical monitoring system can include a light source that directs a light beam toward the substrate during polishing
Implementation Method 3
a detector that measures light reflected from the substrate, and a computer that analyzes a signal from the detector and calculates whether the endpoint has been detected
Data Source
AI summary
A polishing system includes a polishing pad having a solid light-transmissive window, an optical fiber having an end, and a spacer having a vertical aperture therethrough. A bottom surface of the spacer contacts the end of the optical fiber, a top surface of the spacer contacts the underside of the window, and the vertical aperture is aligned with the optical fiber.