Abstract
Despite the potential of phase shifting masks to extend projection optical imaging to higher resolution or lower ki, several issues remain to be investigated before the technology can be fully used. This paper addresses the effects of phase and transmission errors on the alternating-element phase shifting method, otherwise known as the Levenson technique, for printing closely packed lines and spaces. Aerial image simulation is used to generate exposure-defocus trees and the normalized depth of focus k2 is used as the criteria based on given assumptions of linewidth tolerance and exposure allowance. Response surfaces are generated to define the tolerance limit for the phase and the transmission errors which affect both the depth of focus and the center focus. The dependency of these errors on ki, A, and NA are discussed.