Positive and Negative Photolithographic Deposition of Titanium Dioxide from Photosensitive Titanium Complexes

Abstract

Lithographic deposition of titanium oxide films using photochemical metal organic deposition from titanium (IV) complexes is demonstrated in this paper. In this paper we explore the chemistry of thin films of titanium (IV) di-n-butoxide bis(2-ethylhexanoate), titanium (IV) di-n-butoxide bis(2-ethyl-2-hydroxybutyrate), titanium (IV) diisopropoxide bis(2,4-pentanedionate), and titanium (IV) diisopropoxide bis(ethyl acetoacetate). These complexes could all be prepared by ligand exchange reaction from the appropriate precursors. Thin films of each of these compounds could be cast by spin coating from solutions. All the complexes underwent photodecomposition to form titanium dioxide films although only titanium (IV) di-n-butoxide bis(2-ethylhexanoate) did so without the formation of an intermediate. Since all of the precursors were soluble negative lithography resulted in the direct deposition of titanium dioxide from these precursors. In contrast we were only able to demonstrate positive lithography on all the films except those constructed from titanium (IV) di-n-butoxide bis(2-ethylhexanoate). Positive lithography was conducted by exposing a region developing to remove film in the exposed regions followed by blanket exposure to convert the remaining regions to titanium dioxide. Patterns of titanium oxide with a feature size of 1 micron and a resolution of 1 micron were routinely achieved by both positive and negative photolithography. These precursors are also potential candidates for deep UV lithography in fabricating features of sub-50 nanometres.