X-Ray Mask Fabrication Techniques for Micromachning

In this paper we present specifics of X-ray mask fabrication suitable for high-aspect ratio micro-lithography in micromachining. Results of fabrication and exposures using x-ray masks with 4.tm thick gold absorber (one level resist) are illustrated. For conventional x-ray masks commercially available substrates were used: B-doped Si membrane (2-3.tm thick) on a 4 " Si wafer bonded to a Pyrex glass ring. A new approach- the transfer mask technique- is demonstrated. This technique is based on forming an absorber pattern directly onto the resist surface of the sample. The transfer mask method is suitable for any radiation (visible, UV, and X-rays) and is based on the use of a master mask (optical or x-ray) to achieve patterns with desired aspect ratio. When used in conjunction with multiple x-ray exposures and sequential developments the transfer mask method produces patterns with extremely high aspect ratio