Effect of Polishing Pad Material Properties on Chemical Mechanical Polishing (Cmp) Processes

Abstract

ABSTRACTChemical mechanical polishing (CMP) technology has successfully met the stringent requirements of ultraplanarized surfaces in semiconductor manufacture. Commonly, polyurethane based pads have been used to achieve this level of planarization. Recent studies have shown that the material properties of polishing pads used in the CMP process strongly influence the ability to reduce topography. In addition, past work has shown that in the absence of pad regeneration, polishing rate drops dramatically with polishing time. This decrease in material removal rate is believed to coincide with deterioration of the pad surface due to “cold flow” and/or “caking” of the pad material. This study attempts to correlate the intrinsic polymer properties and cellular structure of the pad material to CMP process indices like polishing rate and planarity. For example, the drop off in removal rate as a function of time can be attributed to the mechanical response of polyurethanes under conditions of critical shear. Moreover, planarity achieved is a function of pad stiffness - which itself is dependant upon intrinsic polymer stiffness and cell density.