Improved Charge-Trapping Nonvolatile Memory with Dy-doped HfO 2 as Charge-Trapping Layer and Al 2 O 3 as Blocking Layer

We have investigated a charge-trapping nonvolatile memory (NVM) device with high- k dielectrics as a charge-trapping layer (HfO 2 and Dy-doped HfO 2 ) and a blocking layer (Al 2 O 3 ). Compared with a conventional SiO 2 /Si 3 N 4 /SiO 2 stack, both SiO 2 /HfO 2 /Al 2 O 3 and SiO 2 /Dy-doped HfO 2 /Al 2 O 3 stacks show significantly improved program and erase ( P / E ) speed. The improvement in P / E speed characteristics can be explained by the larger band offset of HfO 2 and the increased thickness of the blocking oxide, which are the main advantages of high- k materials. Moreover, for a SiO 2 /Dy-doped HfO 2 /Al 2 O 3 stack with an optimum Dy concentration, the enhanced retention characteristics were observed at a measurement temperature below 150°C due to the deep energy level of the charge trap.