Real-time Control System for Improved CMP Pad Profiles

Abstract

Chemical mechanical planarization (CMP) pads require conditioning to maintain the surfaces yielding optimal performance. However, conditioning not only regenerates the pad surface but also wears away the pad material and slurry transport grooves. Non-optimized conditioning may result in non-uniform pad profiles, limiting the productive lifetimes of pads. A new approach to conditioning uses closed-loop control (CLC) of conditioning sweep to enable uniform groove depth removal across the pad, throughout pad life. A sensor integrated into the conditioning arm enables the pad stack thickness to be monitored in situ and in real time. Feedback from the thickness sensor is used to modify pad conditioner dwell times across the pad surface, correcting for drifts in the pad profile that may arise as the pad and disk age. Pad profile CLC enables uniform reduction in groove depth with continued conditioning, providing longer consumables lifetimes and reduced operating costs.

Approaches to Sustainability in Chemical Mechanical Polishing (CMP): A Review

“…The current pad life has been increased to approximately 20-40 h depending on the users and processes; in terms of the number of wafers processed per pad, more than 2000 wafers can be polished with a single pad [99]. The reasons for this improvement can be summarized as the development of a high-precision conditioning system to realize low-pressure conditioning technology, a diamond conditioner that can maintain the cutting ability even at low pressures, and real-time pad profile control technology [100,101].…”

“…Finally, the core of the conditioning profile control technology constitutes the development of a real-time pad profile measurement technology and a method to control the weighting function of the conditioning strength according to the pad radius using the result of profile measurement [104]. Using this technology can extend the pad lifespan and maintain pad thickness reduction below the required limit during the pad lifespan [100,101].…”

Real-Time Prediction of Removal Rate and Friction Coefficient During Chemical Mechanical Polishing Using Motor Load Currents with a Polisher

“…[11][12][13][14] The majority of the process is automated, and most polishers for semiconductor devices are equipped with a variety of sensors, including a film thickness meter, to enable various realtime measurements while polishing. 15,16 In particular, endpoint methodologies for adjusting film thickness play a key role in semiconductor CMP, and endpoint methodologies using optical, 17 platen load current (torque sensor), [18][19][20] and piezo electronic sensor 21 methods are commonly employed.…”