(Digital Presentation) Evaluation of the O₃ and H₂o Oxidants in Downscaling Eot of Ferroelectric Hf_0.5Zr_0.5O₂ on Silicon

Integrating the HfZrO2 (HZO) on silicon have attracted the attention of researches in the development of ferroelectric field effect transistor (FeFETs) for implementation in high-density memories and neuromorphic devices[1][2]. In this work, it has been investigated the thickness scalability of HZO thin films and the reduction of the equivalent-oxide-thickness (EOT) on Silicon using [(CH3)2N]4Hf and [(CH3)2N]4Zr as precursor and H2O and O3 as oxidants by means of atomic layer deposition. A TiN/HZO/Si structure was fabricated where the Si substrate has been prepared with a HF-last clean to remove the native oxide or SC1-last clean process to form a chemical oxide layer of 1.2nm. The EOT vs thickness analysis shows an interesting alteration in the dielectric constant which is understood as a phase formation in the HZO from the amorphous to the ferroelectric o-phase to be found in the 4 to 5nm region when annealed at 400 °C. Also, the interface thickness between silicon and HZO was reduced when the HZO is scaled down below the transition region and it is confirmed by transmission electron microscopy (TEM). This reduction in the interface is expressed as scavenging effects from the TiN top electrode when the samples are annealed at 400 °C. [1] J. Y. Kim, M.-J. Choi, and H. W. Jang, “Ferroelectric field effect transistors: Progress and perspective” APL Mater., 9, 021102 (2021) [2] E. T. Breyer, H. Mulaosmanovic, T. Mikolajick, and S. Slesazeck, “Perspective on ferroelectric, hafnium oxide based transistors for digital beyond von-Neumann computing,” Appl. Phys. Lett, 118, 050501 (2021)