The researchers — who are based at Tsinghua University, Beijing InnoMem Technologies Co., Ltd and the Beijing Microelectronics Technology Institute — increased the endurance to 10⁷ cycles through device-, circuit- and operation-level optimization. On the device level, the team introduced an interface modulation layer between the hafnium oxide (HfO_x)-based resistive switching layer and oxygen exchange layer. This regulated the oxygen vacancies at the interface and confined them to areas around the filaments. An annealing step was used to reduce oxygen vacancies created at the sidewalls during the fabrication process, which causes the formation of conductive filaments that cannot be reset. This decreased the defective bits from around 48 bits per 4 Mb to zero — a measured yield of 100%.

On the circuit level, the researchers created a joint-current-limiting method to reduce issues with the write operation and a self-adaptive operation voltage method that adaptively adjusts the compliance and bit line/source line voltages according to the cell address to reduce the forming-loop error rate. A reverse operation is also implemented that reduces the impact of unstable bits. Three embedded RRAM 2 kb cells at randomly selected positions on the wafer show no overlap of the high- and low-resistance states after 10⁷ cycles and exhibit a retention of around 12 years at 125 °C.