The Development and use of Novel Precursors for Photolytic Deposition of Dielectric Films

Abstract

The use of ultra-violet light in the deposition of electronic materials from the gas phase is a rapidly emerging technology. Many of the conventional MOCVD precursors that are available however do not absorb light strongly at wavelengths above 200nm and it is, therefore, often necessary to resort to wave lengths of less than 200nm, where most organic materials have significant absorptions. An alternative approach is to synthesize precursors containing chromophores which specifically absorb at wavelengths that are more easily accessible. We have used this approach to produce a number of precursors, for the deposition of A1₂O₃, with photo-absorption in the 240nm to 300nm range. Basing our work on aluminium tri-isoproxide it has been possible to substitute one of the isopropoxide groups with a β-diketonate group, which forms a six-membered conjugated ring with the aluminium atom. Depending on the nature of the λ-diketonate, these components have absorptions in the 230-320mm range, with molar extinction coefficients in excess of 10,000 at λmax. The low temperature deposition of A1₂0₃ for some of these compounds in the presence of UY light from a high pressure Mercury Xenon arc lamp (with a large spectral output between 260 and 320nm) and the frequency doubled line of an argon ion laser (257nm) is discussed.