Spherical Cell Polishing Pad for Stable Planarizing
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Solution Overview
Problem
Conventional polishing pads for optical materials and semiconductor wafers have poor durability and planarizing characteristics due to their elongated cell structure and low mechanical strength, leading to instability in polishing rate and difficulty in maintaining surface quality over time.
Innovation Solution
A polishing pad with a thermosetting polyurethane foam polishing layer containing roughly spherical interconnected cells, composed of an isocyanate component with 90% diphenylmethane diisocyanate and an active hydrogen-containing compound with 60-98% polycaprolactonepolyol, which provides improved durability and hydrophilicity, allowing for rapid slurry permeation and stable polishing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polishing pads with elongated cell structure are used, then initial polishing performance is achieved, but durability and planarizing characteristics deteriorate over time
Solution Approach 1:
The patent applies spheroidality by transforming the conventional elongated cell structure into a roughly spherical cell structure. The spherical cells have a diameter of 10-100 μm and provide uniform mechanical strength in all directions, preventing the directional weakness and collapse that occurs in elongated cell structures. This spherical geometry maintains consistent planarizing characteristics and durability throughout the polishing pad's service life.
Solution Approach 2:
The patent uses composite materials by combining specific polymers (polyurethane, polyester, polyacrylic acid, or polyacrylonitrile) with controlled molecular weights and functional groups. The composite foam structure integrates spherical cells with a specific density range (0.03-0.6 g/cm³) to achieve both high durability and sustained planarizing performance, overcoming the limitations of single-material conventional pads.
2Productivity
If polishing pads with low mechanical strength are used, then initial polishing is performed, but polishing rate becomes unstable
Solution Approach 1:
The spherical cell structure provides isotropic mechanical strength, meaning the polishing pad maintains uniform strength in all directions during compression and rotation. This prevents the uneven collapse and deformation that occurs in elongated cell structures, ensuring stable polishing rate throughout the pad's operational life.
Solution Approach 2:
The patent controls the density parameter of the foam structure within the range of 0.03-0.6 g/cm³ and specifies cell diameter of 10-100 μm. By optimizing these parameters, the polishing pad achieves the right balance between mechanical strength for stability and porosity for slurry permeation, maintaining consistent polishing rate.
3Ease of manufacture
If conventional wet curing method is used, then polishing pad is formed, but surface layer mechanical strength is low
Solution Approach 1:
The patent specifies composite foam materials made from particular polymers (polyurethane, polyester, polyacrylic acid, or polyacrylonitrile) with controlled molecular weights. These composite materials inherently provide higher mechanical strength to the surface layer while maintaining the ease of wet curing manufacturing process.
Solution Approach 2:
The patent optimizes the molecular weight parameters of the constituent polymers and the density of the foam structure (0.03-0.6 g/cm³). By controlling these parameters, the surface layer achieves enhanced mechanical strength that prevents collapse during polishing while remaining compatible with conventional wet curing manufacturing.
4Loss of time
If polishing pads with poor slurry permeation are used, then surface contact is maintained, but dummy polishing time increases
Solution Approach 1:
The patent utilizes porous spherical cell structures with diameters of 10-100 μm and density of 0.03-0.6 g/cm³. This porous structure provides excellent slurry permeation pathways, allowing slurry to quickly reach the polishing surface and reducing dummy polishing time while maintaining good slurry fit and contact.
Solution Approach 2:
The spherical cell geometry creates numerous uniform pores throughout the polishing pad structure, providing consistent slurry permeation in all directions. This spherical porosity structure enables rapid slurry penetration without compromising the surface contact quality, reducing the time needed for polishing stabilization.
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 polishing pad maintains high planarizing characteristics over time, reduces dummy polishing time, and prevents scratches, while ensuring effective slurry fit and water permeation, enhancing the overall polishing efficiency and surface quality.
Implementation Method 1
the polishing layer comprises a thermosetting polyurethane foam containing roughly spherical interconnected cells having an aperture
Implementation Method 2
ensuring effective slurry fit and water permeation
Implementation Method 3
the polishing layer has the absolute value of a change rate between compressibility A in the dry condition and compressibility B in the wet condition
Data Source
AI summary
A method for manufacturing a polishing pad that has high level of optical detection accuracy and is prevented from causing slurry leak from between the polishing region and the light-transmitting region includes preparing a cell-dispersed urethane composition by a mechanical foaming method; placing a light-transmitting region at a predetermined position on a face material or a belt conveyor, continuously discharging the cell-dispersed urethane composition onto part of the face material or the belt conveyor where the light-transmitting region is not placed; placing another face material or belt conveyor on the discharged cell-dispersed urethane composition; curing the cell-dispersed urethane composition to form a polishing region including a polyurethane foam, so that a polishing sheet is prepared; applying a coating composition containing an aliphatic and/or alicyclic polyisocyanate to one side of the polishing sheet and curing the coating composition to form water-impermeable film; and cutting the polishing sheet.