As device sizes reduce in size and processes become more complex, enhancement techniques for optical lithography are essential. Several ways to enhance the current lithographic systems include immersion lithography, phaseshifting masks, optical proximity correction and OAT (off-axis illumination). Depending on the process, these RETs (resolution enhancement techniques) may be used individually or in combination to compensate for image degradation caused by optical diffraction and resist behavior. The purpose of this project is to design and test a quadrupole off-axis illumination aperture for the 193 nm Immersion stepper at RIT. Process window simulations, using Prolith, were used to determine theoretical effectiveness and benefits for offaxis illumination conditions. The targeted features of 100 nm and 80 nm respectively, each with a duty ratio of (1:1), were processed and compared to simulations. Improvements in terms of (DOF) Depth of Focus and resolution, have been demonstrated for 100 nm and 80 nm features. Off-Axis Illumination and Liquid Immersion are cost effective techniques to extend the lifetime of optical lithography.
Summers, Derek J.
"Quadrupole Illumination Design for a 193nm Hyper-NA Exitech Immersion Stepper,"
Journal of the Microelectronic Engineering Conference: Vol. 14
, Article 9.
Available at: http://scholarworks.rit.edu/ritamec/vol14/iss1/9