Polishing Pad Window With Debris Drainage Groove
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Solution Overview
Problem
Polyurethane polishing pads lack sufficient transparency for effective laser or optical endpoint detection during polishing, leading to insufficient signal strength and potential polishing defects due to debris accumulation in recessed windows.
Innovation Solution
A polishing pad with a transparent window having a concave surface and a debris drainage groove that slopes downward, allowing for improved debris removal and maintaining signal strength by directing debris into the pad, thereby reducing the risk of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transparent window is used for optical endpoint detection, then signal transmission is enabled, but debris accumulates in the recessed window surface causing polishing defects
Solution Approach 1:
The window surface is segmented into multiple functional regions: a central recessed region for optical signal transmission and a peripheral raised region with debris drainage grooves. This segmentation allows the window to simultaneously enable optical detection while providing debris removal pathways that prevent polishing defects.
Solution Approach 2:
Different regions of the window are given different functional properties: the central region is optimized for optical transparency and signal transmission, while the peripheral region is designed with debris drainage grooves and raised surfaces to actively remove and channel debris away from the polishing area, preventing defects.
2Illumination intensity
If the recess is made deeper to accommodate window curvature, then optical path is maintained, but slurry and debris block the optical path reducing signal strength
Solution Approach 1:
The window is divided into a central recessed region that maintains optical path and a peripheral raised region with drainage grooves. This segmentation allows the recess to be deep enough for optical curvature while the peripheral raised regions prevent slurry and debris from blocking the optical path, maintaining signal strength.
Solution Approach 2:
The potential harm of debris accumulation in recesses is converted into a benefit by designing drainage grooves that actively channel debris away from the optical path. The raised peripheral regions create beneficial flow paths that use centrifugal force during rotation to remove debris, transforming a potential defect into an effective debris removal mechanism.
3Ease of manufacture
If the window is made coplanar with the polishing surface, then manufacturing is simplified, but debris accumulates on the window surface creating defects
Solution Approach 1:
The window is segmented into a central coplanar region that simplifies manufacturing and installation, and a peripheral raised region with debris drainage grooves. This segmentation maintains ease of manufacture while adding debris removal functionality that prevents polishing defects through active debris channeling.
Solution Approach 2:
The window design transitions from a two-dimensional coplanar surface to a three-dimensional structure with raised peripheral regions and drainage grooves. This dimensional change adds debris removal capability while maintaining coplanarity at the central optical region, balancing manufacturing simplicity with defect prevention.
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
Enhances optical signal strength and reduces the risk of polishing defects by effectively removing debris from the polishing area, ensuring reliable endpoint detection and maintaining transparency.
Implementation Method 1
rotating the polishing pad with polishing fluid in the debris drainage groove sends debris from the central region into the polishing pad through the debris drainage groove
Implementation Method 2
The light source directs a light beam, passing it through a transparent window toward the substrate being polished. The light detector measures light reflected from the wafer substrate that passes one more time back through the transparent window.
Data Source
AI summary
The polishing pad is suitable for polishing or planarizing at least one of semiconductor, optical and magnetic substrates. The polishing pad has a polishing surface, an opening through the polishing pad and a transparent window within the opening in the polishing pad. The transparent window has a concave surface with a depth that increases with use of the polishing pad. A signal region slopes downward into the central region for facilitating debris removal and a debris drainage groove extending through the central region into the polishing pad. Rotating the polishing pad with polishing fluid in the debris drainage groove sends debris from the central region into the polishing pad through the debris drainage groove.