RRAM Device Design And Mechanisms Research Based On HfO₂

The Flash memory encounters technological difficulties with the decreasing feature sizeof integrated circuit. Resistive switching random access memory (RRAM) is non-volatilememory device. The fact that RRAM has simple structure of metal-insulator-metal (MIM),nanoseconds level programming speed and high integration density has great chance to be thenext generation non-volatile memory as flash memory candidate. Then RRAM attracts moreresearch groups’ attentions, and study of resistive switching mechanism, low powerconsumption and multi-level states is a hot area of research.In this paper, low power device with sub-500nA reset current and three stable resistancestates were achieved through stack engineering based on understanding the resistive switchingmechanisms.Firstly, a considerable conductive TiN electrode was deposited by applied a highsubstrate bias. A sub-nA surface roughness of HfO2was obtained through improvingdeposition conditions.Secondly, we studied conduction mechanism of low/high resistive state in simpleNi/HfO2/TiN structrue.Thirdly，a6-nm thickness of TiOxfilm was obtained by rapid thermaloxidation(RTO) process, the TiOxwith a low resistance can play a electron injection layerbased on its lower work function. Then Ni/HfO2/TiOx/TiN structure was fabricated using theRTO TiOx. With the RTO process, the AlOxwas oxided from Al film at the same condition.Both Ni/HfO2/TiOx/TiN and Ni/HfO2/AlOx/TiN structures show a low power consumption,and the reset current can decrease to sub-100nA.Finally, a VOxdielectric film was introduced into HfO2RRAM application.Al/VOx/CuO/Cu has a compliance characteristic, then it can be seried with Ni/HfO2/TiOx/TiNdevice to form a compliance device-a RRAM device (1C1R) configuration. Moreover,Cu/VOx/HfO2/TiN structure performs low power consumption and three stable resistancestates behaviors.In conclusion, low power device with sub-500nA reset current and three stable resistancestates were achieved through stack TiOx, AlOx, VOxrespectively with different resistiveswitching mechanisms.