Blended CMP Polishing Pads for Temperature-Stable Modulus
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Solution Overview
Problem
Conventional polishing pads for chemical mechanical planarization (CMP) experience undesirable variations in polishing performance due to temperature-induced changes in modulus and hardness, particularly in urethane materials, which are sub-optimal for consistent polishing of substrates with micron-scale and nanometer-scale features.
Innovation Solution
The development of polishing pads composed of a blend of thermoplastic polyurethane and styrenic polymers, which maintain a stable modulus between 25°C and 60°C, with moduli ranging from 30 MPa to 1000 MPa, incorporating precisely shaped pores and asperities for improved consistency and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional urethane polishing pads are used, then material removal is achieved, but polishing performance varies due to temperature-induced changes in modulus and hardness
Solution Approach 1:
The patent employs a composite material system consisting of a thermoplastic polyurethane matrix combined with styrenic polymer particles (such as polystyrene, polyacrylonitrile, or acrylic acid). This composite structure allows the soft polyurethane matrix to provide cushioning and conformability while the dispersed styrenic particles act as reinforcing fillers that maintain structural integrity and mechanical properties across temperature variations, thereby resolving the contradiction between achieving material removal and maintaining consistent polishing performance
Solution Approach 2:
The patent modifies the physical and chemical parameters of the polishing pad by controlling the glass transition temperature (Tg) of the styrenic polymer particles to be above the operating temperature range (25°C to 60°C). This parameter selection ensures the particles remain in a glassy, rigid state during polishing, providing thermal stability. Additionally, the patent optimizes the weight percentage of styrenic particles (1-50 wt%) and their size distribution to achieve optimal balance between softness for conformability and hardness for dimensional stability under temperature variations
2Reliability
If the modulus of urethane polishing pads is increased to improve consistency, then polishing performance becomes more stable, but the glass transition temperature increases making the material sub-optimal for consistent polishing
Solution Approach 1:
The patent applies local quality by creating a heterogeneous structure where styrenic polymer particles are dispersed throughout the polyurethane matrix. The styrenic particles provide localized regions of high rigidity and thermal stability (with Tg above operating range), while the polyurethane matrix maintains overall softness and flexibility. This spatial distribution of different material properties allows the pad to exhibit consistent polishing performance without requiring a uniformly high glass transition temperature throughout the entire material
3Ease of operation
If polishing pads are made softer to improve conformability, then substrate contact is improved, but temperature-induced hardness variations increase
Solution Approach 1:
The composite structure of soft polyurethane matrix with rigid styrenic particles creates a material that exhibits both conformability and hardness stability. The soft matrix allows the pad to conform to substrate contours, while the dispersed rigid particles act as thermal anchors that resist hardness changes during temperature fluctuations, effectively decoupling conformability from thermal sensitivity
Data Source
AI summary
A polishing pad includes a textured polishing layer comprising a working surface and a second surface opposite the working surface. The textured polishing layer comprises a polymeric blend comprising thermoplastic urethane in an amount of between 40 and 95 wt. %, and styrenic copolymer in an amount of between 5 and 60 wt. %, based on the total weight of the textured polishing layer.