Feasibility of ultra-low k1 lithography for 28nm CMOS node

We have designed the lithography process for 28nm node logic devices using 1.35NA scanner. In the 28nm node, we face on the ultra-low k1 lithography in which dense pattern is affected by the mask topography effect and the oblique-incidence. Using the rigorous lithography simulation considering the electro-magnetic field, we have estimated accurately the feasibility of resolution of the minimum pitch required in 28nm node. The optimum mask plate and illumination conditions have been decided by simulation. The experimental results for 28nm node show that the minimum pitch patterns and minimum SRAM cell are clearly resolved by single exposure.