Formation mechanism of interfacial Si-oxide layers during postannealing ofTa2O5/Si

The Si-O-Si bonds formed at the Ta2O5/Si interface by annealing were invest igated by using Fourier transform infrared absorption spectroscopy. The Ta2 O5 thin films deposited on Si substrates were annealed in different ambient (H2O, O-2, and N-2) at temperatures between 500 and 800 degreesC. When ann ealing is done in H2O, the interfacial silicon-oxide grows very rapidly, be cause the oxidation species can easily diffuse through Ta2O5 films, and bec ause the Si-O formation is controlled by the diffusion of H2O in the interf acial layer. When annealing is done in O-2, the oxidation species can also easily diffuse through Ta2O5, but not through the interfacial layer. The in terfacial layer is formed by a reaction between Ta2O5 and Si even if the an nealing ambient does not contain oxidation species, as is the case when ann ealing is done in N-2. We conclude that the Si-O formation during postannea ling in O-2 and N-2 is controlled by the diffusion of the Si from the subst rate through the interfacial layer with an activation energy of 0.7 to 0.8 eV, and that new Si-O bonds are formed at the interface between the Ta2O5 a nd interfacial layer. Oxidation species from the annealing ambient enhance the frequency factor of the reaction, but do not control Si-O formation. (C ) 2001 American Institute of Physics.