INTERDIFFUSION AT THE AL2O3 TI INTERFACE STUDIED IN THIN-FILM STRUCTURES/

The early-stage interfacial reactions between amorphous Al2O3 (a-Al2O3 ) and crystalline alpha-Ti (c-Ti) thin films were studied in thin-film structures with two different thicknesses. Smooth silicon (111) subst rates were covered firstly with a TiN thin-film diffusion barrier and then with a crystalline Ti layer. Finally, amorphous Al2O3 was sputter deposited onto the crystalline Ti layer, The samples were heated in a differential scanning calorimeter with a linear heating rate of 40 de grees C min(-1)-from room temperature up to different final temperatur es of 350-700 degrees C in an argon atmosphere to activate reactions a t the a-Al2O3/c-Ti interfaces-and then rapidly quenched. The interdiff usion at the a-Al2O3/c-Ti interface was studied using the rate of chan ge of the reaction width obtained from Auger electron spectroscopy (AE S) sputter depth profiles. The beginning of the reaction, which involv es the diffusion of oxygen (followed by Al) into the c-Ti thin film, w as observed at similar to 425 degrees C. The activation energy at the a-Al2O3/c-Ti interface was found to be 1.6 eV for the oxygen diffusion from the amorphous Al2O3 into the c-Ti thin film between 425 degrees C and 650 degrees C, and 0.9 eV for the Al diffusion between 500 degre es C and 625 degrees C, The new crystalline reaction product is compos ed of alpha(2)-Ti3Al phase and a solid solution of oxygen in alpha-Ti. The influence of different sample structures on kinetic quantities is discussed. (C) 1998 John Wiley & Sons, Ltd.