<title>Nanometer x-ray lithography</title>

Abstract

New developments for X-ray nanomachining include pattern transfer onto non-planar surfaces coated with electrodeposited resists using synchrotron radiation X-rays through extremely high-resolution masks made by chemically assisted focused ion beam lithography. Standard Ultraviolet (UV) photolithographic processes cannot maintain sub-micron definitions over large variation in feature topography. The ability of X-ray printing to pattern thin or thick layers of photoresist with high resolution on non-planar surfaces of large and complex topographies with limited diffraction and scattering effects and no substrate reflection is known and can be exploited for patterning microsystems with non-planar 3-D geometries as well as multisided and multilayered substrates. Thin conformal coatings of electro-deposited positive and negative tone photoresists have been shown to be X-ray sensitive and accommodate sub-micron pattern transfer over surfaces of extreme topographical variations (over 100 microns). Chemically assisted focused ion beam selective anisotropic erosion was used to fabricate X-ray masks directly. Masks with feature sizes less than 20 nm through 7 microns of gold (aspect ratio ∼ 350) were made on bulk silicon substrates and X-ray mask membranes. The technique is also applicable to other high density materials. Such masks enable the primary and secondary patterning and/or 3D machining of Nano-Electro-Mechanical Systems (NEMS)s over large depths or complex relief and the patterning of large surface areas with sub-optically dimensioned features.