Self-compliance RRAM characteristics using a novel W/TaO x /TiN structure.

Self-compliance resistive random access memory (RRAM) characteristics using a W/TaO x /TiN structure are reported for the first time. A high-resolution transmission electron microscope (HRTEM) image shows an amorphous TaO x layer with a thickness of 7 nm. A thin layer of TiO x N y with a thickness of 3 nm is formed at the TaO x /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 >10(3) 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 TaO x layer at the W/TaO x 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 TaO x switching material. The memory device also exhibits long read endurance of >10(6) 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 >10(4) s is also obtained.