Impacts of O3 Pulse and Post Annealing Process on the Ferroelectric Properties of ALD HfxZr1-xO2 Thin Film

Abstract

Research on ferroelectricity has been studied intensively since ferroelectric properties in the doped-HfO2 thin film were first reported in 2011. Thanks to overcome the issues of scaling and compatibility with CMOS devices, which have been pointed out as problems of ferroelectric materials such as Pb(Zr,Ti)O3(PZT) and SrBi2Ta2O9(SBT) that have been studied before. HfO2 thin film has been spotlighted especially in the field of semiconductor memory devices such as ferroelectric random access memory (FeRAM), ferroelectric field effect transistor (FeFET) and the newly proposed negative capacitance field effect transistor (NCFET). Various methods for improving the ferroelectric characteristics in HfO2 thin films have been studied with several factors of doping, mechanical stress, and film thickness. In particular, to maximize the ferroelectric properties using doping certain elements into HfO2 thin film, several doping elements of Si, Zr, Y, Al, Gd, Sr, and La have been suggested. Among the reported dopants, Zr is the most promising because of the similar physical and chemical properties to those of Hf. With this regard, much research has been done on Zr-doped HfO2 (HfxZr1-xO2) ferroelectric thin film materials, but there is still a need for systematic research. In this study, we have studied the impacts of reactant ozone (O3) pulse and post annealing process on the ferroelectric properties of atomic layer deposition (ALD) HfxZr1-xO2 thin film in TiN / HfxZr1-xO2 /TiN capacitor. For the Metal-Ferroelectric-Metal (MFM) device, electrical properties and physical measurements such as XRD, XPS, XRR, and SEM were performed to observe the ferroelectric properties and phases in the HfxZr1-xO2 thin film. By optimization, the best ferroelectric characteristics are attained when HfxZr1-xO2 thin film is processed with O3 pulse of 3 seconds (s), indicating that the double remnant polarization (2Pr) is 32 μC/cm2 and about 88% increase when cooling in water confirmed. The results suggest that ferroelectric properties can be significantly modulated by O3 pulse during ALD ferroelectric-thin film and post annealing cooling process.