Materials science in semiconductor processing vol:7 issue:4-6 pages:197-202
We report on a low-temperature electron spin resonance (ESR) study of (100)Si/HfO2 entities with ultrathin layers of amorphous (a)- HfO2 deposited by distinct chemical vapor deposition (CVD) techniques using chemically different precursors. The incorporation of N is revealed in (100)Si/HfO2 structures with ultrathin a-HfO2 films deposited by CVD using Hf(NO3)(4) as precursor: Upon Co-60 gamma-irradiation, a prominent ESR powder pattern is observed, which via ESR measurements at two observational frequencies has been incontrovertibly identified as originating from NO2 radicals (density greater than or equal to 55 at ppm). The molecules are found to be stabilized and likely homogeneously distributed in the a-HfO2 network. Based on symmetry considerations, it is suggested that during deposition, N is incorporated in the HfO2 network as neutral Nequivalent toO(3) precursors, which are transformed into ESR-active NO2 radicals upon gamma-irradiation. The N incorporation appears inherent to the particular nitrado CVD process, an aspect that may bear on the electrical properties of the insulator, such as, e.g., introducing charge traps. (C) 2004 Elsevier Ltd. All rights reserved.