Zone plate focused soft X-ray lithography

The zone plate focused soft X-rays of a scanning transmission X-ray microscope have been used to pattern poly(methyl methacrylate) and poly(dimethylglutarimide) films by a direct write method which is analogous to lithography with a focused electron beam. The lithographic characteristics of both polymers have been determined for 300 eV X-rays. With low doses (1 MGy), developed lines 40±5 nm wide were created in poly(methyl methacrylate). At higher doses an exposure spreading phenomenon substantially increases the lateral dimensions of the developed patterns. The spreading mechanism has been identified as the point-spread function of the zone plate lens. The performance of focused soft X-ray lithography is compared to other direct write methods. The practicality of a dedicated focused soft X-ray writer instrument is discussed.