Ion Beam Lithography Using Membrane Masks

Ion beam lithography was performed using 450–500 keV protons and membrane masks in order to show its good potential as a next generation lithography (NGL) tool. By both simulation and experiment using channeling mask, it is shown that a sub 100 nm pattern can be generated with practical mask-to-wafer distances (∼ 10 µm). The angular distribution of protons emerging from the channeling mask was measured to show a very narrow width, which is of vital importance for good lateral line definition. A computer simulation was performed to simulate the proton dose distribution in the resist and to optimize the mask thickness. A comprehensive procedure for fabricating a channeling mask is described. The image replication of the mask pattern at the resist by proton irradiation shows the good potential of the method as a NGL tool.