A study of patterning 36nm-pitch logic contact holes in a metal oxide resist using a high-reflectance phase-shifting mask that results in image reversal

Abstract

High-reflectance phase-shifting mask (HR-PSM) is studied for patterning 36nm-pitch logic contact holes and compared with other mask absorbers in terms of imaging performance (ILS, LCDU, MEEF, etc.) and exposure dose. To this end, wafer-data-calibrated EUV resist models for CAR and MOR are used. Our simulation results show that a HR-PSM produces dark-field images at large mask CD. However, as mask CD decreases, the tone of the images is reversed and bright-field images of good contrast can be generated. Based on this observation, a HR-PSM plus MOR patterning approach is proposed for through-pitch logic contact hole applications with a minimum pitch equal to 36 nm. We show that this approach demonstrates multiple enhancements in terms of through-pitch performance and enables us to extend the practical resolution of logic contact holes below the pitch of 40 nm using the 0.33NA EUV scanner.

Source mask optimization (SMO) study for high-NA EUV lithography to achieve single patterning on random logic metal

“…To print trenches, two combinations are primarily necessary: the dark-field masks in conjunction with positive tone resist, specifically chemically amplified resist (CAR) and the bright-field masks paired with negative tone resist, particularly metal oxide resist (MOR). In the process of optical modeling, this is achieved by modifying aerial image-blur parameters to mimic the resist behavior of CAR and MOR 4,5 .…”