Electrical evaluation of defects at the Si(100)/HfO₂ interface

This work examines the electrical activity of defects at the interface with Si(100) for HfO₂ thin films (10-20 nm) deposited by injection metal oxide chemical vapor deposition. Based on an analysis of the capacitance-voltage response of gold/HfO₂ /Si(100) structures, two clear peaks are detected in the interface state density profiles, at specific energies in the lower (E_v + 0.22-0.28 eV) and upper (E_v + 0.93-0.97 eV) bandgap. The densities of defects responsible for these peaks have been calculated as 1.8-2.4 × 10¹² and 7.3-9.1 × 10 ¹² cm^-2, respectively. These defects are present when the HfO₂ films were deposited at sufficiently low temperatures (T ≤ 350°C) to prevent hydrogen passivation. The density of interface defects was not significantly different for HfO₂ films deposited on native oxide or hydrogen-terminated silicon surfaces. The position of these defects in the silicon bandgap corresponds to the location of P_b0(/P_bl) dangling bond defects in the thermally oxidized Si(100)/SiO₂ system. HfO₂ films deposited at 450°C did not exhibit the prominent interface defects observed on films deposited at T ≤ 350°C, indicating hydrogen passivation during deposition.