A Model for Polychromatic Photoresist Exposure in Optical Microlithography

Computer codes which simulate the photolithographic process are open-loop problem solvers: given the inputs and parameters, a result is predicted. Control theory, as suggested herewith, may help in closing the feedback loop and allow process design and optimisation. As an example, polychromatic exposure is dealt with, which aims at reducing the standing wave effect. Resist activator dynamics and the scalar field equation are included. A minimisation problem is defined, to which complex Lagrangian theory is applied. Optimal inputs can be searched for by an algorithm of which the flow chart is given.