Mechanical Property Control of Low-k Dielectrics for Diminishing Chemical Mechanical Polishing (CMP)-Related Defects in Cu-Damascene Interconnects

Abstract

The dielectric constant dependence of the mechanical strength and the adhesion strength is investigated using porosity-controlled low- k films, and a material parameter is clarified to suppress the chemical mechanical polishing (CMP)-related defects in Cu damascene interconnects. Mechanical strengths such as the modulus and hardness of low- k films decreased as the dielectric constant decreased. Adhesion energy between the low- k films and an upper hard-mask layer (HM) of PECVD-SiO 2 strongly depends on the dielectric constant of low- k films, while adhesion energy between the low- k films and a lower etch stop layer (ES) of SiCN shows weak dependence. It was found that the adhesion energy between the upper SiO 2 and the low- k film is a critical mechanical parameter for diminishing the CMP-related defects. Introducing a porous low- k film, methylsilsesquiazane ( k =2.64), with high adhesion to the HM-SiO 2 , we successfully fabricated single damascene copper interconnects within an acceptable limit of CMP-related defects.