Dry resist process development toward depth of focus improvement in high NA EUV lithography

Abstract

High numerical aperture (NA) extreme ultraviolet lithography enables device scaling and improves resolution. However, it also brings the challenge of reduced depth of focus (DOF) due to the optics with increased NA. New resist innovations are being targeted toward addressing this patterning challenge. We present how dry deposited and dry developed resists can be used to improve the focus window. Modulating the resist composition in the vertical direction and co-optimizing the process conditions have shown benefits in improving patterning metrics, including DOF. Test vehicles based on bright field pitch 32 nm hexagonal contact hole with 0.33 NA and pitch 18 nm line/space imaging with 0.55 NA are discussed to showcase the patterning improvements.