Comparison between memory characteristics of MONOS memory with LaON/SiO2 or HfON/SiO2 as dual-tunnel layer

Abstract

Memory characteristics of MONOS memory with LaON/SiO2 or HfON/SiO2 as dual-tunnel layer were comparatively investigated. Experimental results show that the MONOS memory with LaON/SiO2 as dual-tunnel layer exhibits large memory window, high program/erase (P/E) speed, good endurance and retention properties. The basic mechanism lies in the large dielectric constant of LaON which increases the injection efficiency of carriers during programming/erasing, the smaller Oxygen diffusion coefficient in LaON which leads to the reduction of interface traps and thus the leakage of stored charges through trap-assisted tunneling during retention. Moreover, strong La-N, Hf-N and O-N bonds are formed at/near the interface due to Nitrogen incorporation, which effectively decreases the damages of the P/E cycle stress to the interface, and thus achieves excellent endurance. In addition, impacts of annealing temperatures on characteristics of MONOS memory were investigated. It is demonstrated that the memory annealed at 800 ℃ has better memory properties than that annealed at 700 ℃, which is attributed to the fact that the 800 ℃ NO annealing can incorporate more N into LaON (HfON), and well release strains, thus reducing defects in these dielectrics.