Application of Electro-optical Modulation Technique in Lithography Alignment

The construction and phase detection theory of off-axis alignment system in projection photolithography are introduced in detail. The method of restraining the stray light using (electro-)optical phase modulator is proposed extensively. The alignment accuracies are analyzed and compared when the stray light exists or not. Results show that the alignment accuracy is obviously improved by the (electro-)optical modulation. Thus, electro-optical modulation is one of the effective technologies to improve the alignment accuracy in projection photolithography.