Thermal stability of thin amorphous Ta-Si-N films used in Au/GaN metallization

Ta-Si-N ternary barrier films were obtained by reactive rf magnetron sputtering of a Ta5Si3 target in an Ar-N2 gas discharge. The films were tested as diffusion barriers between Au and GaN layers. The efficiency of these films as diffusion-suppressing barriers is determined by transmission electron microscopy, secondary-ion mass spectroscopy, and X-ray diffraction analysis. It is shown that the diffusion barrier with optimized properties (Ta34Si25N41) in an Au/GaN metallization system can be used to advantage at temperatures above 800°C. A correlation between the composition, microstructure, resistivity, thermal stability, and diffusion-suppressing properties of the films is discussed.