Boosting non-volatile memory performance with exhalative annealing: A novel approach to low-temperature crystallization of hafnia based ferroelectric

Abstract

In this study, we propose a CMOS-compatible exhalative annealing (EA) method that can significantly reduce the annealing temperature of Zr-doped hafnia-based ferroelectrics (HZO). Compared to the conventional rapid thermal annealing (RTA) process, our EA process reduces the crystallization temperature (T_cryst) of HZO films across all thickness ranges (5–10 nm). In particular, a 5 nm-thick HZO film, which is ideal for future 3D semiconductor devices, exhibited a 50 % reduction in T_cryst from 500 °C to 250 °C. X-ray photoelectron spectroscopy (XPS) analysis reveals that the EA method reduces both residual carbon and oxygen vacancy concentrations. High-resolution transmission electron microscopy (HRTEM) confirmed a significant reduction in interfacial mixing between HZO and the electrodes. Capacitors made of Molybdenum (Mo) electrode/HZO/Mo electrode structure annealed using EA at 250 °C exhibited 2 orders of magnitude reduced leakage current at 3 MV cm⁻¹, along with robust ferroelectric properties (2Pr and 2Ec values of 36.7 μC cm⁻² and 2.38 MV cm⁻¹, respectively). Implementing our method to ferroelectric field effect transistors (FeFETs) on a wafer scale resulted in a 33 % increase in their memory window. The CMOS-compatible EA method is effective for producing ferroelectric field-effect transistors on a wafer scale and is well suited for the fabrication of next-generation hafnia-based ferroelectric nonvolatile memory. EA holds great promise for developing future semiconductor devices due to its industry-friendly process and minimal thermal damage.