X-ray lithography

Abstract

X-ray lithography with wavelengths between 0.2 and 5 nm provides both high-structural resolution as good as 0.1 μm and a wide scope of advantages for the application in circuit production. Examples for this better process performance compared to optical techniques are: lower particle and dust sensitivity, applicability of simple single-layer resist technique, high depth of focus without any influence of substrate material and chip topography, and presumably, the highest throughput of all lithography methods which are able to go into the submicron range. However, the introduction of x-ray lithography into the semiconductor production means a revolutionary change of production technology. This begins with a completely different mask technology which makes, for example, the classical separation of mask substrate fabrication from pattern generation by different manufacturers very problematical and ends with the necessity to introduce x-ray lithography in relatively large production capacity units consisting of a larger number of x-ray steppers. The latter is caused by the fact that a storage ring—even in the smallest version, e.g., COSY (Kompakt Speicherring für Synchrotronstrahlung)—has to supply up to 10 x-ray steppers with light in order to clearly beat the optical techniques with respect to throughput and lower cost level. To prove such statements in pilot production lines, the necessary tools and components for x-ray lithography are already or will be available for the first time on a commercial basis in the very near future. Especially steppers, sources, and resists with satisfying specifications have been announced by a growing number of vendors. The most critical problem at present is the mask technology and the tools for defect elimination. However, with the existing technologies, the requirements for 0.5-μm-design rules will be met very soon on a pilot scale.