Investigation on Analysis and Design of Pad Conditioning Process in Double Side Polishing

Abstract:
As polishing proceeds, the pad surface is likely to be covered with polishing residues and by-products, among other things, that can adversely affect removal rates and causes of defects on the wafer surface. Pad surface must be mechanically conditioned with diamond-coated disk to maintain stable polishing performance. However, conditioning can create nonuniform pad wear and gradient. This may cause a nonuniform pressure distribution at the interface between the pad and wafer, and induce the deterioration of polishing qualities such as total thickness variation (TTV) and flatness of the wafer. In addition, the pad is often changed earlier than its intrinsic life due to the excessive pad wear at a certain pad region. This study focused on the pad wear profile during conditioning. The pad wear amount and its profile induced by mechanical conditioning were modeled based on Preston’s equation and kinematic analysis, and the effects of process conditions on the pad wear profile in double-sided polishing. On the basis of modeling and simulation, the effects of various kinematic conditions on pad wear profiles were investigated. From the results, we could find the theoretical analysis and design method of conditioning process to improve pad wear nonuniformity. Keywords: Double Side Polishing, Conditioning, Pad Wear Model, Process Design