Recessed Transparent Window Polishing Pad Design
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Solution Overview
Problem
Existing polishing pads with transparent windows face issues such as scratching, limited usable lifetime, and adhesion problems due to differences in material properties, leading to non-uniform polishing and increased manufacturing costs.
Innovation Solution
A polishing pad design featuring a recessed transparent window with a peripheral portion of polishing material, where the window is non-porous and the peripheral portion is coplanar with the window, reducing stress and protrusion, and enhancing frictional forces for improved adhesion and longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent window is inserted into the polishing pad using adhesive or separate materials, then optical signal transmission is enabled, but adhesion issues and scratching defects occur due to material property differences
Solution Approach 1:
The transparent window is formed from the same polishing material as the surrounding pad body, ensuring homogeneous material properties throughout. This eliminates adhesion issues between different materials and prevents scratching defects that arise from material property mismatches at interfaces.
Solution Approach 2:
The polishing pad incorporates a composite structure where a transparent polymer component is integrated with the polishing material matrix. This composite design maintains optical transparency while preserving the mechanical and chemical properties of the polishing material, eliminating the need for separate adhesive bonds between dissimilar materials.
2Illumination intensity
If a transparent window is made coplanar with the top polishing surface, then optical access is maximized, but stress concentration and protrusion occur leading to reduced pad lifetime
Solution Approach 1:
The top surface of the transparent window is recessed below the top polishing surface by a predetermined amount (0.05-2.0 mm). This preliminary geometric modification prevents stress concentration and protrusion that would otherwise occur at a coplanar interface, thereby extending pad service life while maintaining adequate optical access for endpoint detection.
3Duration of action of stationary object
If the window region is recessed to prevent protrusion, then pad lifetime is extended, but optical signal strength may be reduced
Solution Approach 1:
The recess depth is precisely controlled within the range of 0.05-2.0 mm to optimize the balance between extending pad lifetime and maintaining optical signal strength. This parameter optimization ensures that the window remains sufficiently recessed to prevent protrusion and stress concentration, while not being so deep as to significantly attenuate the optical signal required for 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 design minimizes defects and extends the usable lifetime of the pad by reducing stress and protrusion, maintaining optical signal integrity, and preventing scratching, thereby improving polishing uniformity and reducing manufacturing costs.
Implementation Method 1
the window region comprises a transparent window that has an exposed top surface and an exposed bottom surface to enable light to transmit through the polishing pad in the window region
Data Source
AI summary
A polishing pad for chemical mechanical polishing comprising a polishing layer having a top polishing surface, a bottom surface and a thickness. The polishing layer comprises a porous polishing material and a window region. An exposed top surface of the transparent window is recessed from the top polishing surface. The transparent window extends from the recess region to the bottom surface of the polishing pad. The transparent window is non-porous and a portion of the top surface of the peripheral portion adjacent to the transparent window is coplanar with the top surface of the transparent window and the exposed bottom surface of the transparent window is coplanar with the bottom surface of the polishing layer.