Fabrication Of WOx-RRAM And Explore Of Its Resistance Switching Mechnism

In recent years, due to the huge demand for storage market, non-volatile storagetechnology is developing rapidly, the feature sizes of traditional Flash memory that based onthe structure of floating gate are close to or reach its physical limits, Meet its developmentbottleneck. Among various kinds of new type non-volatile memory, resistance random accessmemory (RRAM) attracts the attention of the scientific research workers, for its simplestorage unit structure, can shrink feature sizes, fast speed, low power consumption,multi-value storage potential, three-dimensional stack, as well as the characteristics of lowcost. In this paper, we study a kind of WOx RRAM, which compatible with CMOS processand easy preparation. Look for ways to improve device performanced and reduce the powerconsumption, and the resistance change mechanism of the device has analyzed preliminary.This article uses metal tungsten target deposition tungsten oxide film with dc reactivemagnetron sputtering, and the crystal orientation and surface morphology of the tungstenoxide thin films have been characterized by X-ray diffraction (XRD), atomic forcemicroscope (AFM). Nonvolatile storage characteristics of the RRAM units have been testedby semiconductor parameter analyzer (SPA). Through the linear fitting of the I-V curves inSET and RESET process combination with the temperature dependence of the tungsten oxidefilm, we explore its resistance change mechanism.Specific research contents and results are as follows:1、A simple Al/WOx/Cu structure RRAM is prepared. After300℃annealing, WOxfilms are primarily (110) crystal phase of WO2.9. Device has good bipolar RRAMcharacteristics, a relatively small operating voltage (Vset=1.6V, Vreset=-0.9V), resistancechange rate of more than three orders of magnitude, good endurance (1000cycles), and goodretention (10000s). The Cu filaments formed in WOx film and the changing numbe of the Cufilaments are the dominant mechanism.2、 Based on Cu electrode under thermal oxidation treatment, we prepared theAl/WOx/CuOx/Cu RRAM with laminated structure. Compared with the single layer structure,laminated structure has higher device yield, close to100%; Lower and more consistentForming, SET and RESET voltages, smaller operating current; more than four orders ofmagnitude lower power consumption. The Cu filaments formed in functional layers in lowresistance state, when high resistance state, Cu filaments disconnect, and schottky barrierformed at the interface between electrode and functional layer, the current transmission ismainly schottky launch.3、Under30S thermal oxidation of Cu electrode, we successful prepared the unipolarAl/WOx/CuOx/Cu structure RRAM. The device has good nonvolatile storage features withForming-free characteristics. Through analyzing the current transmission mechanism, wefind that the oxygen vacancy conductive filaments are formed in low resistance state, andwhen high impedance state, the oxygen vacancy conductive filaments have been broken,current transmission is dominated by effect of space charge limited current (SCLC).