Beamlines for thin and thick resist X-ray lithography

An X-ray lithography beamline is being built for Louisiana State University (LSU), Center for Advanced Microstructures and Devices (CAMD) that uses two plane mirrors at 26 mrad to establish a simple exposure station. An optional asperic mirror substituted for the first mirror can increase the throughput manifold. The second mirror is used for scanning and for horizontal beam propagation. We have investigated the optimum coatings for X-ray lithography with respect to radiation dose delivered to the silicon wafer. Wafer irradiation can be minimized by using titanium as the reflecting surface on one of the surfaces. Wafer doses are reduced by a factor of 2 compared to two gold reflecting surfaces. There is some decrease in overall beamline throughput with a titanium reflector, but given the high flux of the LSU ring, system performance is not degraded. We have also designed a beamline for use for thick (50 μm or grater) resists that uses a single iridium-coated aspheric focusing mirror at 10 mrad incidence angle. This system would be suitable for micromachining where the sample is translated past the beam. The theoretical throughput in 75% at 2 A and when operated with the LSU synchrotron at 1.4 GeV and 200 mA, will expose a 2 in. x 2 in. field of view of 100 μm thick PMMA to > 4 kJ/cm3 in 100 s. The X-rays are at near normal incidence over the entire field. This beamline is also suitable for operation on a superconducting wiggler insertion device (orig.)