Proximity-effect correction in electron-beam lithography on metal multi-layers

We report a proximity-effect correction in electron beam patterning when fabricating a spin valve device with a junction size of 100 nm · 100 nm. Since the spin valve device has a stack of magnetic/non-magnetic/ magnetic metal multi-layers on oxidized Si substrate, its proximity effect should be appropriately corrected to realize a nano-scale junction. ZEP 520A was chosen as an electron beam resist because its dry-etching resistance is high enough to serve as an etching mask in the post-process. A set of proximity parameters, a, b, and g of ZEP 520A coated metal multi-layers was evaluated by using the doughnut pattern method. A simulation was carried out based on given proximity parameters in order to obtain effective dose factors of each segment of the exposure pattern. The junction with a desired shape and size on a metal multi-layer was successfully fabricated with a help of efficient proximity-effect correction.