Characterization of 45 nm Attenuated Phase Shift Mask Lithography with a Hyper Numerical Aperture ArF Tool

概要

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In the 45 nm half pitch node, a mask induced polarization effect appears. Because of this effect, intensity of diffracted light depends on a pattern size and a diffraction order. This is pronounced in an attenuated phase shift mask (attPSM). A mask topography effect has to be considered for rigorous simulation. A small window attributable to diffraction efficiency is generated, because of an insufficient ratio of 1st order and 0th order diffracted light from the attPSM. Two approaches to produce a sufficient ratio, namely, a low transmittance layer attPSM and a biased pattern attPSM, were investigated by simulation. A mask bias of more than 10 nm on both sides is required to generate an optimal diffraction efficiency ratio for the 0th and 1st orders. The low transmittance (around 1%) attPSM had higher contrast at 45 nm half pitch in the resist image than the biased attPSM. It was also shown that a phase difference between diffraction orders caused lower contrast imaging.
2006-06-30