SIMULTANEOUS OPTIMAL BOTTOM LINEWIDTH AND SIDE-WALL CURVATURE CONTROLOF WET ETCHING

Etching is one of the critical steps in the fabrication of microelectr onics devices. A time-optimal control problem with a dual-term termina l cost including both bottom linewidth and side-wall curvature is form ulated to implement an optimal open-width design principle. A singular -are solution does not exist and the control action is bang-bang. The optimal switching time is analytically calculated. The feasibility and effectiveness of this technique are illustrated by simulation studies . This design and control philosophy can easily be applied to other mi croelectronics manufacturing processes.