Particle adhesion and removal in chemical mechanical polishing and post-CMP cleaning

A new model including the effects of polishing pressure and platen speed on particle penetration depth in chemical mechanical polishing (CMP) processes is derived based on the particle adhesion theory, the surface plastic deformation, and the pad-wafer partial contact. The predicted particle penetration depth is in good agreement with the experimental surface roughness data. Particle removal models in the final polishing and mechanical brushing/cleaning processes are proposed, and the removal forces are evaluated. The lift force in the hydrodynamic boundary layer is too small to lift particles off the surface and particles most likely roll off the surfaces by the drag force plus the contact forces from the pad or brush asperities. The effects of pressure, rotation speed, pad hardness, and chemical addition in post-CMP are also addressed. (C) 1999 The Electrochemical Society. All rights reserved.