Application of soft landing to the process control of chemical mechanical polishing
In chemical mechanical polishing (CMP), a two-stage polishing strategy is often employed. A high removal rate (RR) is set at the initial stage, then a lower RR is employed to remove residual metal and extended to the over-polish stage. An analogy between the soft landing of a spacecraft and CMP operation is established and the CMP operation can be viewed as a minimum-time optimal control problem. Measurement uncertainties prevent direct implementation of bang-bang control law for the entire polishing process. Thus, a two-stage CMP operation procedure is devised to ensure robust operation while maintaining a high throughput.
soft landing chemical mechanical polishing minimum time problem damascene sti process control