Diffusion barrier layers for Al on GaAs native oxide grown by liquid phase chemical-enhanced oxidation

Thin films of TiW, TiN/Ti, Pd, and Mo as the diffusion barriers (DB) interposed between the Al layer and GaAs native oxide are examined. The GaAs native oxides are prepared by liquid phase oxidation. The interdiffusion of the Al/GaAs-oxide and Al/DB/GaAs-oxide (DB = TiW, TiN/Ti, Pd or Mo) multilayer structures are investigated by secondary ion mass spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy (AES). The results indicate that TiW and Mo films can effectively block Al diffusion and maintain their structural integrity up to 500 °C and 400 °C for 30 min, respectively. However, the thermal stability of TiN/Ti and Pd films cannot be maintained at 400 °C for 30 min. Moreover, the failure of TiN/Ti barriers due to oxygen incorporated into the barrier layers is observed and the failure of the Pd as the diffusion barrier in the interdiffusion between Al and GaAs oxide, as demonstrated by AES analyses, is also observed.