Recessed Polishing Pad Window for Endpoint Detection
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Solution Overview
Problem
Chemical mechanical polishing pads with integrated windows for endpoint detection face issues such as scratching, limited usable lifetime, and adhesion problems due to differences in material properties between the polishing layer and the window material, leading to non-uniform polishing and increased manufacturing costs.
Innovation Solution
A polishing pad design featuring a porous polishing layer with a recessed non-porous window that extends from the sub-pad to the top polishing surface, preventing direct pressure transmission and reducing stress, while maintaining signal transmission for endpoint detection, and incorporating a peripheral polishing material to enhance flexibility and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transparent window is integrated into the polishing pad for endpoint detection, then endpoint detection capability is improved, but scratching and defects of the substrate occur due to material property differences
Solution Approach 1:
The polishing pad is designed with different material properties in different regions: the window region uses a transparent material with specific mechanical properties matched to the polishing layer, while other regions use standard polishing material. This local differentiation allows optical detection without compromising substrate quality.
Solution Approach 2:
The window material is selected to have mechanical properties (hardness, elasticity, wear rate) that are substantially the same as the polishing layer material, creating homogeneity in mechanical behavior across the pad surface. This prevents the material property mismatches that cause substrate scratching and defects.
2Measurement precision
If a transparent window is used in the polishing pad, then endpoint detection is enabled, but the usable lifetime of the pad is limited due to differential wear rates
Solution Approach 1:
The window material is specifically selected and engineered to have wear rate, hardness, and elasticity parameters that match the polishing layer material. This parameter matching ensures that both materials wear at the same rate, allowing the pad to reach its full intended lifetime without the window becoming the limiting factor.
3Measurement precision
If a transparent window material is used, then signal transmission for endpoint detection is improved, but adhesion issues occur between the window and polishing pad material
Solution Approach 1:
By selecting a window material whose mechanical and physical properties closely match the polishing layer material, the interface between window and polishing layer achieves homogeneous bonding characteristics. This reduces adhesion problems that arise from material incompatibility.
Solution Approach 2:
The polishing pad is constructed as a composite structure with the window material and polishing layer material bonded together. The material selection ensures compatible surface energies and chemical properties at the interface, enabling reliable adhesion while maintaining optical transparency for signal transmission.
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 recessed window design reduces defects, extends the pad's usable lifetime, and minimizes stress-related deformations, ensuring consistent polishing and accurate endpoint detection without the drawbacks of material property differences, thus improving manufacturing efficiency and reducing costs.
Implementation Method 1
a window for transmitting a signal wave through the polishing pad to a substrate to be polished and back through the polishing pad for endpoint detection
Implementation Method 2
a window for transmitting a signal wave through the polishing pad to a substrate to be polished and back through the polishing pad for endpoint detection
Implementation Method 3
the top window surface is recessed from the top polishing surface, the bottom window surface is substantially coplanar with the bottom sub-pad surface, the window extending from the bottom sub-pad surface to the top window surface
Data Source
AI summary
A polishing pad for chemical mechanical polishing comprising a porous polishing layer having a top polishing surface, a sub-pad located opposite from the top polishing surface, the sub-pad having a bottom sub-pad surface, and a window for transmitting a signal wave through the polishing pad to a substrate to be polished and back through the polishing pad for endpoint detection, the window having a top window surface, a bottom window surface, and side edges, wherein the top window surface is recessed from the top polishing surface, the bottom window surface is substantially coplanar with the bottom sub-pad surface, the window extending from the bottom sub-pad surface to the top window surface and the side edges are in contact with the polishing material and the sub-pad material and wherein the window is non-porous.