Abstract
In this thesis, we use the atomic-layer-deposition (ALD) technique with remote-plasma system to prepare high-κ dielectrics, including HfO2, HfO2/La2O3/HfO2 stack, LaHfOx alloy and HfO2 with LaTiOx capping layer on H-terminated silicon substrate for MOSFET gate oxide application. Besides, the HfON and Al2O3 were also deposited by ALD for the charge trap memory application. In Chapter 4, the HfO2/La2O3/HfO2 stack and LaHfOx alloy were deposited as gate dielectric to discuss the effect on material and electrical properties of HfO2 with La2O3 incorporation. It shows that the La2O3 incorporation can enhance the crystallization temperature, raise the dielectric constant and lower the leakage current of HfO2 thin film. In addition, the La2O3 would diffuse to the high-κ/Si interface and consume the interfacial lower-κ SiO2 layer to form the higher-κ silicate then decreasing the EOT value after 900oC PDA. In Chapter 5, we fabricated 5 nm thick HfO2/La2O3/HfO2 stack structure with different La2O3 locations to investigate the La2O3 location effect in HfO2 gate oxide. The vertical location of La2O3 layer was accurately controlled by atomic layer deposition (ALD). From the results, we found that the La2O3 position affects the flat-band voltage (VFB) and thermal stability. Besides, from the In-plane X-ray diffraction (IPXRD) results, we found that a specific La2O3 position can make the crystal structure of HfO2 transfer to a cubic phase which shows higher permittivity (~40) than that of monoclinic phase (~19). In Chapter 6, a thin HfO2 film with a lanthanum titanate (LaTiOx) capping layer has been grown by our homemade remote-plasma atomic layer deposition (RPALD) system. Capacitance-voltage (C-V) and current-voltage (I-V) measurement were done to discuss the electrical characteristics, such as equivalent oxide thickness (EOT), flatband voltage (VFB), hysteresis window, and leakage current density (Jg@VFB-1V). Cross-sectional high resolution transmission electron microscopy (HRTEM) images were obtained to examine the morphology and microstructure of the high-κ film. The chemical composition and binding structure of the sample were analyzed by x-ray photoelectron spectroscopy (XPS). From the results, we found that HfO2 thin film capped with LaTiOx exhibit lower EOT, higher permittivity, and smaller hysteresis window than pure HfO2. Finally, in Chapter 7, the charge storage characteristics of a hafnium oxy-nitride (HfON) charge-trapping layer prepared by atomic layer deposition in a metal–Al2O3–HfON–SiO2–Si (MAHNOS) structure are investigated. We found that an ultrathin HfON embedded in MAHNOS has large memory window, sufficient erase speed, and satisfactory data retention. From the relation of erase transient current density (J) versus tunnel oxide e-field (ETUN), we also found that the erase mechanism of MAHNOS depends on electron de-trapping from HfON to Si substrates. However, MAHNOS embedding with a thicker HfON shows a poor data retention due to the increase of crystallization of the trapping layer.