Elemental diffusion study of Ge/Al2O3 and Ge/AlN/Al2O3 interfaces upon post deposition annealing

The thermal stability of Ge/Al2O3 and Ge/AlN/Al2O3 stacks has been systematically studied upon post deposition annealing (PDA) at 400, 500 and 600 °C with nitrogen gas flow. X-ray photoelectron spectroscopy (XPS) with the incident photon energy of 1486.7 eV and synchrotron radiation photoemission spectroscopy (SRPES) with the incident photon energy of 720, 500 and 200 eV have been used to characterize the interface chemistry and the diffusion of Ge-oxides. More aggressive “clean-up” effect takes place with a higher substrate temperature during the atomic layer deposition (ALD) process for the growth of Al2O3 and AlN thin films. A competitive process among the Ge-oxides growth at the Ge/high-k dielectrics interface, the Ge-oxides diffusion, and GeO desorption has been suggested upon PDA treatments. The effective suppression for formation of Ge-oxides by an ultrathin AlN layer has been observed for the samples before PDA and after PDA at 400 °C. Ge-oxide diffusion in proximity to the gate oxide surface has been characterized from the Ge2p3/2 spectra by XPS after PDA at 400 °C for Ge/Al2O3 and Ge/AlN/Al2O3 stacks. The diffusion mechanism is hypothesized by diffusion of oxygen vacancy. Moreover, a significant desorption of GeO occurs after PDA at 600 °C for the AlN passivated sample.