Self-compliance RRAM characteristics using a novel W/TaO x /TiN structure
Thin Film Nano Tech. Lab., Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan 333, Taiwan
Nanoscale Research Letters 2014, 9:292 doi:10.1186/1556-276X-9-292Published: 10 June 2014
Self-compliance resistive random access memory (RRAM) characteristics using a W/TaOx/TiN structure are reported for the first time. A high-resolution transmission electron microscope (HRTEM) image shows an amorphous TaOx layer with a thickness of 7 nm. A thin layer of TiOxNy with a thickness of 3 nm is formed at the TaOx/TiN interface, owing to the oxygen accumulation nature of Ti. This memory device shows 100 consecutive switching cycles with excellent uniformity, 100 randomly picked device-to-device good uniformity, and program/erase endurance of >103 cycles. It is observed that the 0.6-μm devices show better switching uniformity as compared to the 4-μm devices, which is due to the thinner tungsten (W) electrode as well as higher series resistance. The oxygen-rich TaOx layer at the W/TaOx interface also plays an important role in getting self-compliance resistive switching phenomena and non-linear current-voltage (I-V) curve at low resistance state (LRS). Switching mechanism is attributed to the formation and rupture of oxygen vacancy conducting path in the TaOx switching material. The memory device also exhibits long read endurance of >106 cycles. It is found that after 400,000 cycles, the high resistance state (HRS) is decreased, which may be due to some defects creation (or oxygen moves away) by frequent stress on the switching material. Good data retention of >104 s is also obtained.