Extension of krypton fluoride excimer laser lithography to the fabrication of 0.18 μm devices

This article presents the extension of krypton fluoride (KrF) excimer laser lithography. An 0.18 μm device can be fabricated by KrF excimer laser lithography when weak off-axis illumination is combined with an attenuated phase-shifting mask, a high-performance antireflective layer, and a high-numeral-aperture exposure tool. A 1.0 μm depth-of-focus can be achieved for 0.18 μm rule logic patterns. The weak off-axis illumination can reduce the influences of the secondary peak in the high-duty periodic patterns, and retain the depth-of-focus for isolated patterns when it is used in combination with an attenuated phase-shifting mask. A high-performance antireflective layer can increase the depth-of-focus because a uniformly exposed area in the photoresist can be formed when the light reflected from the substrate is eliminated.