Improving Analog Switching in HfO<italic>x</italic>-Based Resistive Memory With a Thermal Enhanced Layer

Analog RRAM with hundreds of resistance levels is an attractive device for neuromorphic computing. However, it is still very challenging to realize good analog behavior in filamentary RRAM cells. In this letter, we developed a novel methodology to improve the analog switching in filamentary RRAM. The impact of local temperature on analog switching behavior is elucidated. The transition from abrupt switching to analog switching is found at higher temperature. Based on this result, a thermal enhanced layer (TEL) is proposed to confine heat in switching layer for realizing analog RRAM. The HfO _x /TEL RRAM shows analog switching characteristics with more than ten times window using 50-ns pulses. Finally, a 1-kb analog RRAM array is demonstrated with uniform analog switching, fast speed, excellent resistance window, and excellent retention properties.