Optimal design and operation of a multiscale GaAs/AlAs deposition process

We consider optimal operating conditions of a gallium arsenide/aluminum arsenide (GaAs/AlAs) deposition process with objectives of uniform deposition of the film heterostructure across the wafer surface at the macroscopic scale and the interfacial uniformity of the GaAs/AlAs heterostructure at the microscopic scale. We use a finite element solver to determine macroscale solutions and kinetic Monte Carlo (kMC) techniques to determine the mesoscale solution of the problem.We characterize the interfaces between species and apply the simulation methodology to a multiscale optimization framework to minimize the interfacial step densities while also minimizing temperature, annealing time, and maximizing thickness uniformity. The design variables are temperature, annealing time, precursor concentration, and input velocity. In order to reduce the prohibitive computational expense of the function evaluations, we employ an in situ adaptive tabulation scheme around the mesoscale inputs. The resulting optimization problem combined with this methodology becomes computationally tractable, and is able to increase the thickness uniformity and maintain low interfacial step densities.