Improvement of Uniformity of Resistive Switching Parameters by Selecting the Electroformation Polarity in IrOx/TaOx/WOx/W Structure

A route to improve the uniformity of key resistive switching memory parameters such as SET/RESET voltages, low/high-resistance states as well as switching cycles is demonstrated in an IrOx/TaOx/WOx/W simple resistive memory stack by selecting the electroformation polarity. The various stack layers are confirmed by high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy analyses. Cumulative probability plots of the key memory parameters show tight distribution. The oxygen vacancy filaments are formed/ruptured owing to polarity-dependent oxygen ion migration, which is the switching mechanism in the TaOx/WOx bilayers, and improved resistive switching parameters under positive formation polarity are observed. The fabricated device has shown good potential for multilevel capability with a low voltage operation of +/- 3 V. The device has shown an excellent read endurance of >10(5) cycles and data retention up to 10 years at 85 degrees C. (C) 2012 The Japan Society of Applied Physics