Printing high-density patterns with dark-field 193-nm lithography

In dark-field (DF) lithography, light from the condenser illuminates the reticle at such a steep angle that non- diffracted light is lost from the system. A DF reticle contains a series of sub-resolution amplitude gratings to diffract light from the condenser into the projection lens and, thus, to precisely control the amplitude, phase and direction of light from every point on the reticle. In this paper we show how DF lithography can be used to print high- density patterns at higher contrast than is currently possible with conventional 193-nm lithography in a single exposure.