Charge trapping characteristics of atomic-layer-deposited HfO₂ films with Al₂O₃ as a blocking oxide for high-density non-volatile memory device applications

Charge trapping characteristics of high-relative permittivity (high-κ) HfO₂ films with Al₂O₃ as a blocking oxide in p-Si/SiO₂/HfO₂/Al₂O ₃/metal memory structures have been investigated. All high-κ films have been grown by atomic layer deposition. A transmission electron microscope image shows that the HfO₂ film is polycrystalline, while the Al₂O₃ film is partially crystalline after a high temperature annealing treatment at 1000 °C for 10 s in N₂ ambient. A well-behaved counter-clockwise capacitance-voltage hysteresis has been observed for all memory capacitors. A large memory window of ∼7.4 V and a high charge trapping density of ∼1.1 × 10¹³ cm ^-2 have been observed for high-κ HfO₂ charge trapping memory capacitors. The memory window and charge trapping density can be increased with increasing thickness of the HfO₂ film. The charge loss can be decreased using a thick trapping layer or thick tunnelling oxide. A high work function metal gate electrode shows low charge loss and large memory window after 10 years of retention. High-κ HfO₂ memory devices with high-κ Al₂O₃ as a blocking oxide and a high work function metal gate can be used in future high-density non-volatile memory device applications.