PROBING POINT DEFECTS AND TRAPS IN STACKS OF ULTRATHIN HAFNIUM OXIDES ON (100)SI BY ELECTRON SPIN RESONANCE: INTERFACES AND N INCORPORATION

摘要

The results of an electron spin resonance (ESR) analysis of (100)Si/HfO_2 entities with ultrathin layers of deposited amorphous (a)-HfO_2 are overviewed. The main ESR signals observed in the as-grown samples and after VUV irradiation were P_b-type interface defects. However, when using Hf(NO_3)_4 as a precursor in chemical vapor deposition (CVD), the incorporation of N is revealed after ~(60)Co γ-irradiation through the observation of NO_2 radicals. The molecules are found to be stabilized and likely homogeneously distributed in the a-HfO_2 network. Some network forming N entity is suggested as a precursor, transformed into ESR-active NO_2 upon γ-irradiation. The interesting N incorporation into the HfO_2 network appears inherent to the particular nitrato CVD process and correlates with dominant electron trapping in these hafnia layers as revealed by electrical measurements in combination with photo-generation of charge carriers. Generally, in the HfO_2 films obtained using other (N-free) CVD chemistry, hole trapping is found to dominate the oxide charging.