ABSTRACT
Originally conceived for the fabrication of smaller microelectronic features, X-ray lithography also has attributes of great utility in micromechanical fabrication. In contrast to the many micromachining processes that have been developed from microelectronic processing, however, X-ray based approaches may be performed largely without a tightly controlled clean-room environment. The mode of X-ray based microfabrication most commonly used places this type of processing in the additive category where a sacrificial mold is used to define the desired structural material. As a result, this technique lends itself to a very rich and ever-expanding material base including a variety of plastics, metals, and glasses, as well as ceramics and composites. The idea of using X-rays to define molds extends from the 1970s when its precedent involved defining high-density coils for magnetic recording read/write heads and high-density magnetic bubble memory overlays. This was where the use of X-rays for Very Large Scale Integration (VLSI) lithography was initially investigated [Romankiw et al., 1970, 1995; Spiller et al., 1976; Spears and Smith, 1972]. The distinction from VLSI X-ray lithography is that the mold or photoresist thickness for micromachining interests is generally much greater than 50 microns and may be well over 1 millimeter. X-ray processing at these thicknesses has prompted the nomenclature deep X-ray lithography, or DXRL, based microfabrication.
