Direct photopatterning of metal oxide structures using photosensitive metallorganics

Abstract

A novel process employing photosensitive metallorganic precursor materials is used to pattern thin-film mixed-metal oxide structures. In this process a photosensitive metallorganic precursor is coated onto a silicon substrate and exposed to ultraviolet light through a mask to form patterned oxide structures or baked at low temperatures to produce blanket metal oxide thin films. In the case of direct photopatterning, a negative-tone process occurs in which the unexposed areas can be washed away using a developer solvent. The photochemical conversion of the precursor films was monitored using transmission Fourier transform infrared ~FTIR! spectroscopy, and lithographic contrast experiments were conducted to estimate the dose required to pattern mixed oxide films of barium, strontium, and titanium. It was determined that the minimum dose required to print an image with the set of precursors investigated in this work was approximately 440 mJ/cm2 for a precursor film thickness of 800 nm. Based on FTIR data, this dose corresponds to removal of approximately 20% of the organic material from the original precursor film. Dielectric properties were measured for photochemically converted oxide films via parallel-plate capacitance testing. The composition of the oxide films produced from a given precursor stoichiometry was determined by using X-ray photoelectron spectroscopy.