Thermally Stable HfO₂-Based Ferroelectric Transistors for CMOS-Compatible Energy-Efficient Neuromorphic Integrated...

HfO₂ based thin-film ferroelectrics are metastable at room temperature and transited to the dielectric monoclinic phase upon heating. The thermal stability of such ferroelectrics increases when thin-film oxides are buried (BOX) in silicon-ferroelectric-silicon (SFS) structures formed by SmartCut^®, where thin ferroelectric layers are stabilized by oxygen vacancies and tensile stresses in the BOX, which is similar to silicon-on-insulator (SOI) structures. The main characteristics of the ferroelectrics in MFS and SFS structures are residual polarization P_r and coercive field E_c, which are determined by the fraction of the metastable ferroelectric phases that are also stabilized due to the inserted Al impurity in HfO₂:Al₂O₃ 10:1 (HAO) and (HfO₂:ZrO₂):Al₂O₃ (1:1)₅:1 (HZAO) nanolaminates. SFS structures and SFS CMOS ICs were tested after all thermal treatments at temperatures 900-1000 °C with t_BOX = 10-20 nm (or equivalent oxide thickness EOT = 1-2 nm) in an industrial process as gate insulators for CMOS and dual-gate DG SFS transistors. Their characteristics simulated in TCAD Sentaurus and analytic models in LTspice are investigated for an analog content addressable memory (ACAM).