CMP Pad Recessed Window for Optical Endpoint Detection
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads allow polishing liquid to leak through the pad, interfering with optical endpoint detection during semiconductor substrate planarization, leading to inaccurate determination of surface planarity and layer thickness.
Innovation Solution
A CMP pad with a recessed region containing a solid light-transmissive window and strategically designed grooves that allow light to pass through, preventing liquid leakage and enabling effective optical monitoring for endpoint detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional CMP pad structure is used, then polishing liquid can flow through the pad freely, but optical endpoint detection is interfered with and measurement precision deteriorates
Solution Approach 1:
The polishing pad is segmented into multiple functional regions: a first region with grooves for liquid flow, a second region with deeper grooves for enhanced flow, and a third region that is substantially groove-free for optical detection. This segmentation allows different parts of the pad to serve different functions simultaneously, preventing liquid leakage into the optical path while maintaining polishing effectiveness.
Solution Approach 2:
The pad structure varies locally across different regions. The third region has a distinct local quality (substantially groove-free) compared to the first and second regions (with grooves), creating a localized area optimized for optical transparency and endpoint detection while other regions handle liquid distribution and removal.
2Object-affected harmful factors
If grooves are added to prevent liquid leakage, then liquid flow control improves, but device complexity increases
Solution Approach 1:
Instead of adding complex sealing mechanisms throughout the pad, the solution segments the pad into regions with different groove patterns. The first and second regions have grooves for liquid management, while the third region is deliberately simplified (groove-free) for optical access, achieving liquid control without excessive complexity.
Solution Approach 2:
The groove pattern is applied locally only where needed for liquid flow control (first and second regions), while the third region maintains local quality optimized for optical detection. This localized approach prevents unnecessary complexity in areas where grooves would interfere with endpoint detection.
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 prevents polishing liquid leakage, allowing for accurate optical monitoring and reliable detection of endpoint conditions, ensuring proper planarization and layer thickness control during CMP processes.
Implementation Method 1
A solid light-transmissive window is secured in the recess. The window is more light-transmissive than the polishing layer.
Implementation Method 2
a detector that measures light reflected from the substrate
Data Source
AI summary
In one aspect, a polishing pad includes a homogeneous unitary polishing layer having a polishing surface, an opposed bottom surface, a recess in the polishing surface extending partially but not entirely through the polishing layer, and a solid light-transmissive window is secured in the recess. In another aspect, a polishing pad includes a polishing layer having a polishing surface, and the polishing surface includes a first region having a first plurality of grooves with a first depth extending partially but not entirely through the polishing layer and a second region surrounded by the first region and having a second plurality of grooves with a second depth extending partially but not entirely through the polishing layer, the second depth greater than the first depth.