Comparison of random telegraph noise, endurance and reliability in amorphous and crystalline hafnia-based ReRAM

Abstract

Resistive random access memory (ReRAM) is a novel form of non-volatile memory expected to replace FLASH memory in the near future. To optimize the switching parameters of ReRAM we investigated fab-friendly HfOx based devices with an either amorphous or crystalline active layers. Our devices are fabricated with a copper bottom electrode, a 50 nm sub-stoichiometric hafnia layer, and a platinum top electrode. These devices operate according to the electrochemical metallization model. We compared endurance, reliability and random telegraph noise (RTN) with pulse-based cycling/readout. Initial endurance measurements show 4 million and 70 million consecutive cycles for the amorphous and crystalline hafnia, respectively. The transmission rate was shown to be slightly higher for the amorphous active layer with a confidence of 85%. Furthermore, it is shown that the relative difference in resistance during RTN is not dependent on the crystallinity, but increases with an increase in high resistive state. A high variety of noise patterns were observed, including transition rates from 1 s-1 up to 12000 s-1 and multi-state traps.