Slurry removal forces involved

The CMP material removal mechanism involves a special combination of chemical and mechanical forces [3]. First, chemically active slurry containing fine abrasive particles is released onto the porous pad and attacks the film to be planarized to chemically modify it. This allows the mechanical action involving a three-body contact motion of pad, abrasive, and wafer under an applied pressure to easily facilitate... 

The CAT mode of operation involves introduction of the adsorbent near the axis of the rotor, allowing the centrifugal force to move the particles radially outward. Liquid introduced at the outer periphery of the rotor moves countercurrent to the adsorbent and is removed at the axis of the rotor. Adsorbent slurry collects at the periphery and is conducted to the rotor axis for discharge. Experiments using activated carbon to adsorb n-butanol from water revealed that the degree of back-mixing is the dominant factor in performance. Back-mixing is a function of rotor speed, density difference between the phases, and the particle diameter (54). 

The chemical-mechanical polishing or planarization (CMP) process is a complex interplay between the wafer and the consumables involved. The consumables include slurry, pad, conditioner, and so on. During polishing, the pad carries the slurry and delivers it to the wafer surface. It also transmits the normal and shear forces from the polisher to the wafer. Therefore, polishing pad plays a critical role in the CMP process and influences the outcomes such as material removal rate (MRR), within-wafer nonuniformity (WIWNU), wafer-to-wafer nonuniformity (WTWNU), step height reduction efficiency (SHRE), and defect counts. 

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