Nucleation and growth of aluminium oxide on silicon in the CVD process

Films of aluminium oxide have been formed on single crystal silicon substrates using AlCl₃-CO₂-H₂ gas mixtures in a cold-walled chemical vapour deposition (CVD) reactor. The nucleation and subsequent growth of the deposit have been observed under the varying process parameters. It is found that the nucleation and growth of the Al₂O₃ are dependent on the H₂O flux and H₂O supersaturation. An activation energy of 34.8 Kcal mol^–1 is obtained for the growth rate indicating that the CVD of Al₂O₃ on silicon is a thermally activated process and limited by surface reaction. Scanning electron micrographs (SEM) show that the deposited films are amorphous at low temperature, 850° C, but change to fine grained polycrystalline structure at high temperature, 1000° C.