A process and method for projection beam lithography which utilizes an estimator,
such as a Kalman filter to control electron beam placement. The Kalman filter receives
predictive information from a model and measurement information from a projection
electron beam lithography tool and compensates for factors which cause beam placement
error such as wafer heating and beam drift. The process and method may also utilize
an adaptive Kalman filter to control electron beam placement. The adaptive Kalman
filter receives predictive information from a number of models and measurement
information from a projection electron beam lithography tool and compensates for
factors which cause beam placement error such as heating and beam drift. The Kalman
filter may be implemented such that real-time process control may be achieved.