Possibilities for Projection X-Ray Lithography Using Holographic Optical Elements

Abstract

Although there is a considerable literature on proximity x-ray lithography [1], the interest in projection x-ray techniques has arisen fairly recently, mainly due to the efforts of the AT and T group [2]. The advantages of the projection approach seem to be the elimination of transmission masks and other problems of close proximity, the opportunity for demagnifying a mask of a coarser spatial scale, and, given a rigid, reflection mask, the possibility of cooling. The assumption behind the pursuit of these advantages is that the technical challenges of making the optical system that will perform the projection and the x-ray source that will illuminate it are tractable on some timescale. The optical fabrication tolerances and other design issues involved in carrying out projection using a conventional reflection system have been investigated by Rogers and Jewell [3]. These authors find that the needed tolerances are well beyond the present state of the art [4] even for spherical surfaces and the required surfaces in these schemes are aspheric. In this presentation we present an alternative approach to the process of projection which, of course, has its own, different challenges. It is a matter of one's judgement and technological starting point to decide which one of these (or other) approaches will provide the easiest path to a working x-ray projection lithography.