(Invited) Towards Metrology to Enable Standardizing CMP Consumables
Authors: Obeng Yaw 
Published: July 2021

In the semiconductor industry, there is a need to establish fundamental, mechanism-based, correlation(s) between process conditions, consumables (e.g., pads and slurries), and observed process performance in Chemical-Mechanical Polishing (CMP) [1-5]. Such understanding can lead to the creation of industry-wide standards that can help reduced cost of ownership. Along these lines, the Chemical Mechanical Planarization Consumables (CMP-C) Task Force under Liquid Chemicals Global Technical Committee within the SEMI Standards Program has been actively developing a guide (SEMI C100) for reporting CMP pad hardness [6], and pad density.

In this paper, we revisit our decades old, but still relevant, quest for suitable mechanism-based metrology for CMP-pad. While we focus on polyurethane-based CMP pads, we will touch on alternative pad materials. [10-11]. Using both static and dynamic the dynamic mechanical analysis (DMA) [7-8] and the FTIR [9] we monitored changes in pad polymer properties under various chemical and mechanical stresses. Pad sample were analyzed: prior to use (fresh); after a 24-hr soak in silica-containing oxide slurry (basic); and after oxide polishing (used). Upon comparison it was observed that a characteristic transition feature due to water is present at sub-ambient temperatures in both the slurry soaked and used pads. Exposure of as-received pads to basic oxide slurry results in a broad, high temperature transition thought to be the result of chemical-induced disruption of macrostructural units. Polishing (load-enhanced chemical exposure) introduces further changes to the polymer network represented by an apparent degradation of the pad polymer.

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