Design of 200nm, 170nm, 140nm DUV contact sweeper high transmission attenuating phase shift mask through simulation. Part 1

Simulations for 140nm, 170nm, and 200nm contacts were optimized on a 18% transmitting phase shift mask. A transmission of 18% is shown to have the most linear aerial image behavior through focus. The simulations were run using a primitive positive photoresist model in order to predict trends in resolution and to predict when side lobes begin printing. The contact hole design was optimized such that the process windows for various pitches overlap and the sidelobes are suppressed. By adding both opaque and clear sub-resolution assist features, the simulations show contacts as small as 140nm resolve with 0.83μm focus latitude and 2.00mJ/cm 2 exposure latitude for a pitch of 0.98μm, and with 0.36μm focus latitude and 0.50mJ/cm 2 exposure latitude for a pitch of 0.44μm. Simulation shows that the serifs which create an effective contact bias also suppress side lobe printing. Vector simulation shows that the coupling between the electric and magnetic fields reduces the peak intensity and side lobe intensity.