Pad roughness evolution during break-in and its abrasion due to the pad-wafer contact in oxide CMP

Chemical-mechanical planarization (CMP) is one of the most demanding process steps in interconnect integration, because it is influenced by numerous variables. Among them is the roughness of the polishing pad. Therefore we systematically characterize the break-in process and the pad surface abrasion due to the pad-wafer contact in absence of conditioning. For this we use the pad roughness characterization methodology presented in [1] to extract important roughness parameters like the mean asperities radius of curvature and the asperity density. The subsequent comparison of the pad surface characteristics at different process stages allows the estimation of the break-in time required to achieve a steady state pad texture that enables stable removal rates from wafer to wafer. In addition, by characterizing the abrasion of the pad asperities due to their interaction with the wafer, the contact height between pad and wafer is estimated and the removal rate decay in the absence of conditioning can be modeled.