Forming-free Resistance Random Access Memory Using Ta 2 O 5 /TaO x Bi-layer Prepared by Magnetron Sputtering Method

This paper describes proposal of ReRAM switching mechanism, development of production tool for ReRAM sputtering and improvement in TaO x -ReRAM switching characteristics. We propose that a ReRAM-cell has stack a structure in which an oxygen vacancy supply layer (TaO x ) and an oxygen accumulation layer (Ta 2 O 5 ) sandwiched by the top and bottom electrodes. Resistance change of the ReRAM-cell is caused by the oxygen vacancies migrating between the TaO x and the Ta 2 O 5 layers by applied voltage. This prediction corresponded to the experimental facts. The thickness of Ta 2 O 5 film sputtered by a mass production tool had good uniformity (±1.0%) and excellent stability (±1.0%). Also the sheet resistance uniformity (1σ) of TaO x film had 3.6%. By examining the sputtering conditions, the ReRAM-cell having a Ta 2 O 5 /TaO x bi-layer operated in less than 100μA with a forming-free and had excellent endurance property to 10 10 cycles at 50nsec.