Spatial light modulator (SLM) maskless lithography, an optical technology that replaces photomasks with an adjustable array of microelectromechanical mirrors can potentially complement conventional, mask-based, lithography. The usefulness of this technology depends on whether it can print features at least as well as conventional tools and can keep pace with the International Technology Roadmap for Semiconductors. In particular, any SLM-based tool developed now must be capable of printing 50 nm or smaller gates and 130 nm pitch lines and spaces using 193 nm light as is being planned for the 65 nm half-pitch node. SLM mirrors may be designed to tilt or shift in depth (piston). Aerial image simulations presented here show that 65 nm node features formed by piston mirrors have the same process latitude as tilt mirrors with a numerical aperture (NA) of 1.1. In addition, piston mirrors exhibit the added benefit that they may be,arranged to mimic alternating aperture phase shift photomasks. Isolated and dense features of 65 nm node dimensions can be printed with a reduced NA of 0.90. This form of phase shifting may be required at the 65 nm ITRS node both for conventional and maskless lithography applications. (C) 2004 American Vacuum Society.