Evolutionary optimization of the electron-beam lithography process for gate fabrication of high electron mobility transistors

An electron-beam lithography simulation tool was realized. This tool models the development of multilayered poly(methylmethacrylate) resist structures after exposure with an electron beam. A development front propagates insid e the resist stack as a function of rime and the local solubility. The loca l solubility was experimentally measured versus the electron dose for diffe rent types of resist. The efficiency of incident and backscattered electron s was determined using doughnut-shaped structures. The ratio of the backsca ttered to incident electron efficiencies eta was found to be 1.35 for an ac celeration voltage of 30 kV on Inf substrates. We used genetic algorithms t o optimize the electron dose necessary for the realization of a given resis t profile. This tool was applied to fabricate T-gates and asymmetric gate r ecesses. (C) 2000 American Vacuum Society. [S0734-211X(00)12006-2].