Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore
doi:10.3850/978-981-18-6021-8_OR-12-0224
Ex-Situ Conditioning Based on Constant Material Removal Rate for a Digital Twin CMP System
1Department of Mechanical Engineering, Pusan National University, 2, Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan, Republic of Korea
ABSTRACT
Conditioning is a process of regenerating the pad surface deteriorated during chemical mechanical polishing (CMP) in order to keep a constant material removal rate (MRR). The state-of-the-art in the CMP conditioning process changes from in-situ to ex-situ in order to reduce the micro-scratches induced by the pad debris generated in-situ conditioning. However, the ex-situ conditioning is required to understand how the pad surface roughness is changed by the CMP, and how long the conditioning time is required to get a constant MRR. In this study, changes of surface roughness and MRR according to polishing pressure and time were investigated, and the minimum conditioning time to recover to the initial state after polishing was also obtained. the authors found that the slope of reduced peak height (Rpk) and pad-wafer real contact area (RCA) increased sharply at higher pressure conditions, requiring a longer conditioning time for sufficient regeneration. When sufficient conditioning was performed, Rpk and RCA returned to their initial state, and the MRR remained constant. Using multiple linear regression techniques on the constructed experimental data, a model for predicting MRR according to pad surface roughness was developed. Finally, it will be possible to realize the automatic process control by building big data of the pad surface roughness by the CMP conditions and applying it to the digital twin.
Keywords: Chemical mechanical polishing (CMP), Conditioning, Surface roughness, Digital twin
1Department of Mechanical Engineering, Pusan National University, 2, Busandaehak-ro 63beon-gil, Geumjeong-gu, Busan, Republic of Korea
ABSTRACT
Conditioning is a process of regenerating the pad surface deteriorated during chemical mechanical polishing (CMP) in order to keep a constant material removal rate (MRR). The state-of-the-art in the CMP conditioning process changes from in-situ to ex-situ in order to reduce the micro-scratches induced by the pad debris generated in-situ conditioning. However, the ex-situ conditioning is required to understand how the pad surface roughness is changed by the CMP, and how long the conditioning time is required to get a constant MRR. In this study, changes of surface roughness and MRR according to polishing pressure and time were investigated, and the minimum conditioning time to recover to the initial state after polishing was also obtained. the authors found that the slope of reduced peak height (Rpk) and pad-wafer real contact area (RCA) increased sharply at higher pressure conditions, requiring a longer conditioning time for sufficient regeneration. When sufficient conditioning was performed, Rpk and RCA returned to their initial state, and the MRR remained constant. Using multiple linear regression techniques on the constructed experimental data, a model for predicting MRR according to pad surface roughness was developed. Finally, it will be possible to realize the automatic process control by building big data of the pad surface roughness by the CMP conditions and applying it to the digital twin.
Keywords: Chemical mechanical polishing (CMP), Conditioning, Surface roughness, Digital twin
