Engineered barriers with hafnium oxide for nonvolatile application

The innovative concept of engineered barriers in the tunnel dielectric stack is very promising for low-voltage nonvolatile memory applications. In this brief, transport in engineered barriers using hafnium oxide (HfO2) as high-k dielectric is experimentally investigated. The structure was of the following type: Al/HfO2/SiO2/Si. Experiments demonstrate that transport at program and erase voltages is limited by traps in the high-k film. Modeling with Poole-Frenkel conduction quantitatively reproduces experiments, with trap parameters derived from high temperature measurements. With respect to a film of pure SiO2 with the same equivalent oxide thickness, real HfO2/SiO2 barriers exhibit lower leakage at low fields because of the greater physical thickness in spite of a much lower conduction at operation voltages. The effectiveness of engineered barriers fatally depends on the electronic features of the high-k dielectric.