Effects of oxygen conditions during deposition on memory performance of metal/HfO2/SiO2/Si structured charge trapping memory

Abstract

In this work, we compare the storage performance of two Al–HfO2–SiO2–Si structured charge trapping memory (CTM) devices, where the charge trapping layer (HfO2) is grown under an anaerobic or aerobic condition, respectively. The device based on the HfO2 film deposited under an anaerobic condition shows a large memory window of 4.1 V at a scan voltage of ±11 V. Moreover, it has better retention characteristics and has a charge loss rate as low as 1.1% after being retained for 104 s. The HfO2 film has a higher oxygen vacancy defect density and is capable of trapping charges more efficiently. We characterize the elemental composition of HfO2 thin films in single-layer CTM devices by XPS. It can be concluded that there are more oxygen defects in the HfO2 films deposited under an anaerobic condition. In addition, the defect states of HfO2 films deposited under both anaerobic and aerobic conditions are investigated by photoluminescence and photoluminescence excitation measurements. It is found that the defect states are distributed in the deep levels from 2.3 eV to 2.9 eV below the conduction band. We provide further insights into the appropriate oxygen condition for the production of CTM devices based on the HfO2 thin films.