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The crystal structure of the volatile bismuth alkoxide tris(1-methoxy-2-methyl-2-propanolato)bismuth(III), Bi(OCMe 2 -CH 2 OMe) 3 , 1, has been determined by single crystal X-ray diffraction (XRD). The complex is mononuclear, containing a sixcoordinate Bi III atom in a distorted octahedral environment. Using a solution of 1 in heptane, thin films of bismuth oxide have been deposited by liquid injection metal±organic (MO) CVD. Deposition was carried out over a wide range of substrate temperatures (250±550 C) and, using Auger electron spectroscopy (AES), films were shown to be pure bismuth oxide (Bi 2 O 3 ) with no detectable carbon.

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tors from their external sources using solenoid or pneumatic valves. Zn was evaporated inside the reactor at 440 C and pulsed onto the substrates by means of inert gas valving [2]. In the TiN process the exposure times were 0.2 s for TiCl 4 and Zn, and 0.5 s for NH 3 , and all the purge times were 0.5 s. These values are the same as those optimized in experiments made on planar substrates, i.e., no special attention was paid to the potential need for longer exposure and purging times in order to transport precursors into and out of the high aspect ratio trenches. For the deposition of Al 2 O 3 , 1.5 s TMA and H 2 O exposure times and 3.0 s purge periods were used.The substrates used for the Al 2 O 3 films were 150 mm silicon wafers covered by about 100 nm thick thermal silicon oxide film. Trench structures with varying aspect ratios were prepared by standard patterning techniques. For the growth of TiN, 5´5 cm 2 pieces were cut from these substrates.

The MOCVD technique is being used increasingly for the deposition of electronic ceramics such as Pb(Zr,Ti)O3, Ta2O5 and TiO2. For the mil potential of MOCVD to be realised, it is sometimes necessary to modify existing precursors so that process parameters in the MOCVD process are optimised. In this paper we describe our approach to “molecular design” and discuss how the substitution of simple alkoxide groups by β-diketonates or donor-functionalised ligands can result in precursors with improved physical properties and optimum MOCVD characteristics.