Impacts of post-metallization annealing on the memory performance of Ti/HfO2-based resistive memory

Abstract

Impacts of post-metallization annealing (PMA) on bipolar resistance switching of Ti/HfOx stacked films were investigated. A Ti capping film as a scavenging layer with assistance of PMA is used to tune the dielectric strength of the 10-nm-thick HfOx layer. The polycrystalline microstructure of 10-nm-thick HfOx seems immune to the temperature of PMA in this work. The initial resistance and forming voltage in the Ti/HfOx devices mitigate as the increment of the annealing temperature. With enough annealing temperature (>450 °C), the device shows a good on/off ratio, high temperature operation ability and robust endurance (>106 cycles). Through the reaction between Ti and HfOx at 500 °C, the abundant oxygen ions are depleted from the insulator and the left charge-defects building conductive percolative paths in the dielectric layer. The operation-polarity independence of the form-free HfOx device in initial state is demonstrated. The forming-free memory with initial low resistance of 800 Ω at 0.1 V can be operated with stable bipolar resistance switching via initially positive or negative voltage sweep. The formless device with 10 nm thick HfOx also exhibits excellent nonvolatile memory performances, including enough on/off ratio, improved HRS uniformity and good high temperature retention (3 × 104 s at 200 °C). The results of this work suggest that the PMA temperature will affect the memory window and cycling reliability of the Ti/HfOx-based resistive memory. Optimum temperature (450 °C) will improve the memory performance of the Ti/HfOx stacked layer.