Effects of mechanical characteristics on the chemical-mechanical polishing of dielectric thin films

Abstract

The effects of as-deposited (intrinsic) stress, externally applied (extrinsic) stresses, hardness, and modulus of various dielectric firms on chemical-mechanical polishing (CMP) removal and post-CMP cleaning processes are studied in this article. Intrinsic stresses of the polished dielectrics do not contribute directly to the CMP removal rate. Extrinsic stresses including normal and shear components are calculated using principles of elasticity and fluid mechanics respectively and their roles in the material removal process are discussed. Theoretical evaluation and experimental results both suggest that hardness and modulus are the two most important material characteristics affecting the CMP process. Efficiency of post-CMP particle extraction can be monitored using an adhesion probability which is related to the hardness of wafer and pad. Tn addition, particle removal rate can be remarkably enhanced by increasing pressure (normal stress) while increasing pad rotation speed (shear stress) contributes little to reduce the particle count.