X-ray lithography: Part I—Design criteria for optimizing resist energy absorption; part II—Pattern replication with polymer masks

An X-ray lithography system is analyzed in terms of maximizing the absorbed energy density in the resist. The individual factors, such as X-ray quantum efficiency, electron-beam energy, wavelength, power dissipated in the anode, and the possible use of an X-ray window are discussed. It is shown that K-line radiation from an Al or Si source is the most efficient for mask membranes of either Si or a thin polymer film without an X-ray window and for a thin Be window. For thick Be windows, L-line radiation sources become more efficient. Fabrication procedures have been developed in our Laboratories for polymer film X-ray masks using both photo and electron-beam lithography. The advantages and disadvantages of such masks are discussed. Etched SiO2patterns made using polymer film masks show excellent replication of the mask patterns.