Application of a Run-to-Run Controller to a Vapor Phase Epitaxy Process

We investigate in this paper a Run-to-Run controller in silicon semiconductor vapor phase epitaxy (VPE). The first analysis leads to the conclusion that the main input parameters are: deposition time and dopant flow, which respectively influence the thickness and dopant concentration on the grown EPI layer. Within the allowed control bounds, the experimental results permit to consider a linear dependence in both relations. Furthermore, a tuning of the silicon gas flow can be added, to guarantee the linearity between time and thickness. In the first control algorithm the exponentially weighted moving-average is applied to both control loops (thickness and doping loops) while in the second one, the Kalman filter is available for the thickness loop only. Both drift and shift disturbances are considered. The optimization of the maintenance is handled by three a priori and two a posteriori check filters. Reliability of the method is investigated. It is shown that the recommended input parameters generated by the Run-to-Run controller loops, together with the imposed filters constraints, guarantee the system stability. The two Run-to-Run systems are validated by means of simulations.