A production demonstration of wafer-to-wafer plasma gate etchcontrol by adaptive real-time computation of the over-etch time from insitu process signals

An adaptive nonlinear controller for wafer-to-wafer plasma etch control is described. It uses real-time process signatures and historical data from a relational database for a computation of the over-etch time for the current wafer etching within the reactor. For an MOS gate etch the standard deviation of the oxide thickness between the gate and the source (or drain) is in the range of 10 Å. This is comparable to open-loop control or timed etch where the operator selects the ideal over-etch time. The controller has thus achieved a minimum of human equivalence and often performs better by 40%