Inorganic hardmask development for EUV patterning
Extreme ultra violet (EUV) patterning offers an opportunity to explore new hardmask materials and patterning approaches. Traditional patterning stacks for Deep UV (DUV) patterning have been based on optimizing multi-layer schemes for reflectivity control and pattern transfer. At EUV wavelength, the patterning challenges are dominated by stochastics and aspect ratio control. This offers an opportunity to think differently about underlayer design for sub-36nm pitch patterning. The choice of hardmask can be used to modulate post-litho defectivity to mitigate the stochastics effects and enable more efficient pattern transfer. Through different case studies this paper will explore a range of silicon-based inorganic hardmasks for sub36nm EUV patterning. How film properties dominate patterning performance will be studied systematically. The relative merits of patterning a chemically amplified organic resist directly on an inorganic hardmask or having different types of organic adhesion promoters as an intermediate layer will be also be presented.