Effect of interfacial SiO_(2-y) layer and defect in HfO_(2-x)film on flat-band voltage of HfO_(2-x)/SiO_(2-y) stacks for backside-illuminated CMOS image sensors

摘要

AbstractIn this study, the effect of oxygen gas fraction during deposition of a hafnium oxide (HfO2−x) film and the influence of the quality of the SiO2−yinterlayer on the nature of flat-band voltage (Vfb) in TiN/HfO/SiO2−y/p-Si structures were investigated. X-ray photoemission spectroscopy analysis showed that the non-lattice oxygen peak, indicating an existing oxygen vacancy, increased as the oxygen gas fraction decreased during sputtering. FromC–VandJ–Eanalyses, theVfbbehavior was significantly affected by the characteristics of the SiO2−yinterlayer and the non-lattice oxygen fraction in the HfO2−xfilms. The HfO2−xative SiO2−ystack presented aVfbof − 1.01 V for HfO2−xfilms with an oxygen gas fraction of 5% during sputtering. Additionally, theVfbof the HfO2−xative SiO2−ystack could be controlled from − 1.01 to − 0.56 V by changing the deposition conditions of the HfO2−xfilm with the native SiO2−yinterlayer. The findings of this study can be useful to fabricate charge-accumulating layers for backside-illuminated image sensor devices.