HfO2-Based Ferroelectric Field-Effect Transistors with 260 nm Channel Length and Long Data Retention

We report the fabrication of highly scaled sub-0.3 μm ferroelectric field-effect transistors on the basis of ferroelectric HfO₂. The electrical properties of 9 nm thick Si-doped HfO₂ films depending on the silicon content and the annealing temperature were investigated. The most suitable fabrication conditions for the emergence of ferroelectricity were identified. The ferroelectric properties were verified up to temperatures of 170°C. N-channel MFIS-FETs (Metal-Ferroelectric-Insulator-Semiconductor Field-Effect Transistors) with poly-Si/TiN/Si:HfO₂/SiO₂/Si gate stack and channel lengths down to 260 nm were successfully fabricated. The switching characteristics, endurance and retention properties were analysed. Switching times of 10 ns were demonstrated. A memory window of 1.2 V was obtained with program/erase voltages of -6.5 V and +4 V and pulses as short as 50 ns. Endurance performance of up to 104 cycles was verified. Retention characteristics were measured at 25°C and 150°C. 10 years data retention was indicated for both temperatures by the extrapolation of the experimental data.