Growth mechanism of aluminium oxide films and factors controlling it in a pulse pressure MOCVD deposition technique using different precursors in organic solvents [article]

Hari Murthy, University Of Canterbury
2017
The aim of this project is to investigate into the growth mechanism occurring in a pulsed pressure MOCVD deposition technique using aluminium oxide films on silicon substrates. Another objective of the study is to look into the effect of the precursorsolvent interaction on the droplet vaporisation mechanism. Commonly used aluminium oxide precursors (aluminium isopropoxide, aluminium sec butoxide, aluminium tert butoxide and aluminium acetylacetonate) and solvents (hexane and toluene) are used
more » ... deposit aluminum oxide films and their properties (film composition, surface morphology, surface roughness, growth rate and surface bonds) are studied. The deposition variables, besides the choice of precursors and solvents, includes precursor concentration, deposition temperature, presence of a shield over the substrate, and external heat to the droplets through a heat tape. The shield is used to test the effectiveness of the precursor-solvent droplet to vaporise and also ensures that aerosols or surviving droplets do not contribute to the film deposition. A model simulating the droplet behaviour and the reactor conditions, developed by Boichot et al. is used to study the aluminium oxide deposition to corroborate the experimental observations. According to the model, external heat assists in the droplet vaporisation process, though the minimum temperature at which any significant effect is observed is 220oC. At such high temperatures, it is likely that the precursors would be decomposed in the gas phase and arrive at the substrate as homogeneous particles. The enthalpy of vaporisation and the specific heat capacity of the solvents is crucial during the droplet evaporation. Solvents with a higher vapour pressure (lower enthalpy of vaporisation) release more material into the vapour phase during the flash vaporisation stage. Following the flash vaporisation, the droplets experience a process of solvent evaporation and precursor evaporation as it approaches the deposition zone. The droplets would arrive at the substrate eit [...]
doi:10.26021/3335 fatcat:5fmhc5xz4fewbbsj4w7ve3ht3q