Increased x-ray power from a transition-radiation source

Abstract

Soft x rays were produced by a stack of 12 aluminum foils, each 1.0 μm thick, which were bombarded by a relativistic electron beam whose maximum power was ∼10 kW. The maximum total soft x-ray flux was measured to be 8 mW, a factor of 10 over the previous value. The maximum average power per unit area was ∼0.3 mW/cm2 over 8.5 cm2 area at 3 m from the transition radiator. Using an Intel mask, we obtained lithographs with features of 0.5 μm. Exposure times of the bare resist were as short as 150 s for 4.3 cm2 of wafer area (the resist had a 230 mJ/cm2 energy dose per unit area). The shortest time for mask/wafer exposure was 300 s for 8.5 cm2. We reduced the exposure time of the photoresist by a factor of 9 from the previous value.