Variations in Tunnel Electroresistance for Ferroelectric Tunnel Junctions Using Atomic Layer Deposited Al doped HfO 2 Thin Films

To enhance the tunneling electroresistance (TER) ratio of a ferroelectric tunnel junction (FTJ) device using Al-doped HfO2 thin films, a thin insulating layer was prepared on a TiN bottom electrode, for which TiN was preliminarily treated at various temperatures in O2 ambient. The composition and thickness of the inserted insulating layer were optimized at 600°C and 50 Torr, and the FTJ showed a high TER ratio of 430. During the heat treatments, a titanium oxide layer formed on the surface of TiN, that suppressed oxygen vacancy generation in the ferroelectric thin film. It was found that the fabricated FTJ device exhibits two distinct resistance states with higher tunneling currents by properly heat-treating the TiN bottom electrode of the HfO2-based FTJ devices in O2 ambient.