A Research Of Preparation And Properties Of Resistance Random Access Memory Based On ZnO

With the rapid popularization of portable electronic products,the demand for integration of memory circuits are highly increasing.The conventional floating gate memory devices have reached a bottleneck period and encounter enormous challenges.In order to cope with these problems,a new generation of memory such as phase change random access memory?PCRAM?,ferroelectric random access memory?FeRAM?,magnetic random access memory?MRAM?and resistance random access memory?RRAM?has emerged.Among them,RRAM has attracted extensive attention from researchers for its simple structure,relatively low energy consumption,well storage density,fast operation speed,good anti-fatigue characteristics and easy to three-dimensional integration.Transition metal oxides such as ZnO,HfO₂ and other components are popular materials for preparing RRAM because of its simple component,low manufacture cost and well CMOS process compatibility.In this paper,ZnO-based and Zn_1-xMg_xO-based RRAM were prepared based on magnetron sputtering.The effects of different process conditions on the microstructure,surface morphology and resistive properties of the films were investigated.The main work is as follows:1?ZnO thin films were prepared on ITO conductive glass by RF magnetron sputtering.The effects of process parameters such as the flow rate of argon to oxygen,sputtering power and sputtering time on the quality and resistive properties of films were investigated.With the increase of oxygen flow,the crystallinity and resistive properties of the films were improved.The resistive properties achieved the best effect when the flow rate of argon and oxygen are 30 sccm and 20 sccm,respectively;The intensity of the diffraction peak grew stronger with the increase of sputtering power,and the crystal quality was optimal when the sputtering power was 120 W,the switching characteristics of the device were relatively well;The thicker film was,the larger forming voltage and Set voltage were required,while Reset voltage was almost unchanged,therefore the power consumption of the device was proportional to the thickness of film;The local area where resistive switching occured depended on the size of the electrode,smaller electrode contributed to more minor resistive switching area,and the resistance was higher in the high resistance state,the switching ratio characteristic was superior.2?The Zn_0.76Mg_0.24O alloy film was prepared by magnetron co-sputtering.The Mg²⁺was effectively incorporated into the ZnO crystal lattice to make the film exhibit ZnO hexagonal fiber ore structure.The required Set and Reset voltage of Zn_0.76Mg_0.24O RRAM was lower compared with the pure ZnO resistive device,the switching ratio was excellent?10³¹0⁴?with in 40 cycles,which has great application potential in the field of resistive memory.The Mg content in the film was increased with the increased of sputtering voltage of Mg target,but Mg²⁺could not fully integrate into the ZnO crystal lattice and caused mismatch,the Zn_1-xMg_xO film transformed into amorphous state and the resistance change property was poor even lost.3?The analysis with the conduction mechanism of Al/ZnO/ITO RRAM shown well fitting with SCLC and PF emission mechanism,the main conduction mechanism can be explained by the PF emission mechanism.Further analysis shown that the resistive behavior was associated with the AlO_x insulating layer formed at the interface of the electrode and film.It was shown that the high impedance state of Al/Zn_1-xMg_xO/ITO RRAM conformed to the SCLC mechanism,and the low resistance state conformed to the ohmic conduction mechanism.