Effects of post-metallisation annealing on surface-interfacial and electrical properties of HfO2/Ge stacks modified in situ with SiO2 interfacial layer

The effects of post-metallisation annealing (PMA) at 400 °C for 30 min in an NH3 ambient on the interfacial and electrical properties of a structure consisting of a Ge substrate coated with HfO2 by atomic layer deposition with a 3-nm-thick SiO2 interfacial layer formed in situ by a sputtering technique were evaluated. X-ray diffraction and x-ray photoelectron spectroscopy analyses confirmed the crystallinity of HfO2 and chemical bonding of the HfO2/SiO2/Ge interface before and after the annealing. Clear stretch-free distinct capacitance-voltage curves were observed for the sample after the PMA. According to the electrical measurements, the sample after the PMA exhibited a large dielectric constant (k ̃ 17), low interface trap density (Dit = 1.8 × 1012 cm2 eV−1), and small oxide charge (Qeff = 2.54 × 1012 cm2 eV−1). The gate leakage current of the PMA device determined using the current-voltage curve was approximately 0.1 × 10−4 A cm−2 at Vg+ = +1 V. These results suggest that the SiO2 interfacial layer formed in situ and NH3−PMA significantly improved the structural, interfacial, and electrical characteristics of the HfO2/Ge stacks for future Ge-based complementary metal-oxide-semiconductor device applications.