Investigation of pad wear in CMP with swing-arm conditioning and uniformity of material removal

Abstract

Chemical mechanical polishing (CMP) process plays the role of planarizing and smoothing the uneven layers after the material deposition process in the semiconductor industry. In this process, pad conditioning using a diamond disk is inevitable to attain a high material removal rate (MRR) and to ensure the stability of the process. Pad conditioning is performed for providing uniform surface roughness and opening up the glazed surfaces of the polishing pad. However, the uneven pad wear resulting from pad conditioning leads to changes in the uniformity of MRR and productivity of the device. In this study, we investigate the pad wear profile after swing-arm conditioning of the pad, based on measurements performed using a pad measurement system (PMS). Conditioning experiments are conducted with seven cases of profiles of the conditioner's duration time (PCDT). In all the cases, “W”-shaped pad profiles are generated through swing-arm conditioning. It is observed that a concave-shaped PCDT results in the lowest value of maximum pad wear rate. The average depth of pad wear (havg) is mainly related to the MRR, and the maximum depth of pad wear (hmax) and the horizontal distance from the wafer center to the position (e) where the maximum pad wear occurs affect the within-wafer non-uniformity (WIWNU). A concave-shaped PCDT results in longer life of the polishing pad by minimizing the variation in pad wear. This paper can provide a technical assistance in selecting the conditioning recipe and improving the lifetime of the polishing pad in the CMP process.