Effect of high-radiation-dose-induced structural modifications of HfSiO4/n-Si on electrical characteristics

Abstract

High-k/n-Si structures were formed with HfSiO4 films annealed at the temperature range of RT (room temperature)-900 degrees C and radiation-induced structural modifications were determined by XRD (X-ray diffraction) and XPS (X-ray photoelectron spectroscopy) techniques in the study. The effect of oxygen-deficient bond contents on the electrical characteristics of HfSiO4 pMOS (n type Metal Oxide Semiconductor) capacitors whose radiation response was investigated in the 0-50 kGy dose range was investigated. While no XRD peak was observed before and after irradiation at RT and 500 degrees C-HfSiO4/n-Si, crystallization started with irradiation at 900 degrees C. The dielectric constant of the film was found in the range of 16-23. It was determined that Hf-Hf oxygen-deficient bonds act as negative charge trapping centers, while Hf-Si and Si-Si oxygen-defective bonds act as positive charge trapping centers. The direction of the C-V (Capacitance-Voltage) curve changed continuously with increasing radiation dose. The change in the interface trap charge density was found to be higher than the change in the oxide trap charge density for all doses in RT-HfSiO4 pMOS capacitor and for 1 kGy at 500 degrees C-HfSiO4 pMOS capacitor. Oxygen defective bond content and Hf-O-Si/Si-O-Si ratios were sufficient to establish a link between structural analyses and electrical characteristics at some doses. In some cases, the frequency-dependent charges had a more dominant effect on the radiation response of the device compared to the oxide trap charges.