Effect of zero bias Gamma ray irradiation on HfO2 thin films

• Published in: Journal of materials science. Materials in electronics 2016-12, Vol.27 (12), p.12796-12802
• Main Author: Maurya, Savita
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Materials Science; Optical and Electronic Materials
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-016-5412-6

Hafnium dioxide was proposed by the researchers as one of the dielectric materials that could be used as dielectric layer in the fabrication of capacitor in MOS-based devices and capacitive RF MEMS switches. In the current work, HfO 2 dielectric layer has been fabricated using ALD technique and the fabricated layers have been investigated under Co-60 gamma irradiation doses up to 1500 krad (SiO 2 ). Crystal structures and the phase of the HfO 2 thin films were studied before and after irradiation using GI-X-ray diffraction, elemental composition was investigated by energy-dispersive X-ray spectroscopy. Capacitance–Voltage (C–V) and Conductance–Voltage (G–V) measurements were measured before and after irradiation at 1 MHz AC frequency. The density of the interface states (D it ) was calculated from measured C–V and G–V characteristics. Dependency of flat band voltage on irradiated dose was obtained from the C–V measurements. Slight decrease in series resistance (R S ) was observed with increase in irradiation dose, which is crucial for the conductance of the device characteristics. D it features improved for higher irradiation doses but still in the order of 10 11  eV/cm 2 . Calculated values of D it were not found to be high enough for Fermi level pinning and so it’s not corrupting the device operation over the given dose range. The effect of irradiation on HfO 2 thin films and MOS system were determined from analysis of measured XRD spectra, C–V and G–V curves.