Fabrication and characterization of ferroelectric hafnium oxide thin film for nonvolatile memories

Abstract

In recent years, there has been increasing demand for the next-generation memory that can replace the current memory devices. Many researchers have devoted their efforts to develop the universal nonvolatile memory devices, such as resistive switching memory, phase change memory, and magnetoresistance memory. Although ferroelectric memory device was first suggested in 1950s, scaling issue and CMOS compatibility problem remain unsolved until the discovery of ferroelectricity in hafnium oxide ($HfO_2$) film. The $HfO_2$ based memory can utilize the current CMOS technologies, and also it is relatively free from the scaling issue. In this thesis, fabrication and characterization of ferroelectric $HfO_2$ film are demonstrated for the application to future nonvolatile memories. By doping small amount of aluminum oxide ($Al_2O_3$) in $HfO_2$ film, ferroelectric property was achieved. The ferroelectric properties were examined depending on the dopant concentration, annealing condition, electrode materials, and deposition order of $HfO_2$ and $Al_2O_3$ in atomic layer deposition. The origin of ferroelectricity in $HfO_2$ film was thoroughly investigated through XPS, ToF-SIMS, GI-XRD, and TEM.