Sub-micron imaging on high-topography wafers using spray coating and projection lithography
We propose a method to image inside deep trenches (50?m) using spray-coated resist and the ASML PAS 5500/100 system with the new functionality multi-step imaging. Multi-step imaging allows extending the focus offset range of the PAS 5500/100 system from30?m to200?m. Isolated trenches and contact holes were both imaged inside the deep trenches and on the surface of the wafer to study the versatility of the new functionality. A resolution of 700nm in 3?m thick photoresist, at the bottom of 50?m deep, 200?m wide trench, was obtained with this process. Finally, multi-focus exposure that consists in exposing the same image several times at various focus offsets was performed in order to image thick photoresist on high topographic substrates.
deep trenches resist spray coating mems 3d structures high topography