Resist profile characteristics caused by photoelectron and Auger electron blur at the resist–tungsten substrate interface in 100 nm proximity x-ray lithography

The replicated resist pattern characteristics caused by photoelectrons and Auger electrons generated from the W substrate were investigated for 100 nm proximity x-ray lithography. In addition, simulations for a hard x-ray spectrum having 2.36 keV average energy were performed to investigate the substrate electron effects in hard x-ray lithography. In the experiments, it was found that the secondary electrons from the W substrate caused undercut and footing of resist profiles at the resist–substrate interface. Several buffer layers with varying thicknesses were tested to reduce the photoelectron effects from the W substrate. The best thickness of the buffer layers for a good resist pattern profile was discovered to be >30 nm. Furthermore, the experimental results were quantitatively compared to the results from computer simulations using the Monte Carlo method. For hard x rays, we predict that the exposure latitude is worse on both W and Si substrates.