Charge trapping characteristics of atomic-layer-deposited HfO_2 films with Al_2O_3 as a blocking oxide for high-density non-volatile memory device applications

摘要

Charge trapping characteristics of high-relative permittivity (high-k) HfO_2 films with Al_2O_3 as a blocking oxide in p-Si/SiO_2/HfO2/Al_2O_3/metal memory structures have been investigated. All high-k films have been grown by atomic layer deposition. A transmission electron microscope image shows that the HfO_2 film is polycrystalline, while the Al_2O_3 film is partially crystalline after a high temperature annealing treatment at 1000 ℃ for 10 s in N_2 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 × 10~(13) cm~(-2) have been observed for high-k HfO_2 charge trapping memory capacitors. The memory window and charge trapping density can be increased with increasing thickness of the HfO_2 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-k HfO_2 memory devices with high-k Al_2O_3 as a blocking oxide and a high work function metal gate can be used in future high-density non-volatile memory device applications.