An Ultrathin Forming-Free $\hbox {HfO}_{x}$ Resistance Memory With Excellent Electrical Performance

Abstract-A forming-free 3-nm-thick HfO_x, resistive memory device is demonstrated. The percolation threshold of insulatingto-conductive transition in the ultrathin HfO_x, can be lowered by using the Ti capping layer with an adequate post metal annealing. By the reaction between Ti and HfO_x,, oxygen ions are depleted from the oxide, and conductive percolative paths, which consist of charged oxygen vacancies, are formed. Without any forming step, the memory can operate with stable bipolar resistance switching by initial positive or negative voltage sweep. Possible scenarios of switching mechanism for the initial state of the device with different sweep directions are proposed. This forming-free device also exhibits an on/off ratio of about ten and excellent memory performances, including high speed (~10 ns), low operation voltages (<; 1.2 V), robust endurance (> 10⁶ cycles), good nonvolatile property (500 min at 85 °C), and 2-b switching per cell.