Increasing throughput in low pressure chemical vapor deposition: an optimal control approach

The application of optimal control theory to the process of low pressure chemical vapor deposition on patterned surfaces can substantially decrease the processing time for a given step coverage, compared with the programmed rate chemical vapor deposition (PRCVD) process. The control model is developed from the simultaneous 1D Knudsen diffusion and chemical reaction description. For such a model, the optimal control problem is formulated as to find a temperature trajectory yielding the minimum processing time and its solution is computed numerically via a modified variation of extremals method. For the thermally activated deposition of silicon dioxide from tetraethylorthosilicate (TEOS) and for a ninety-six percent step coverage, the optimal control-generated temperature trajectory results in time-savings of approximately 28 percent, when compared to the PRCVD approach.