Study On Bending Failure Mechanism Of The 1D1R Type Resistive Memory

Traditional memory represented by flash memory,has come to the bottleneck of size reduction.Among the new non-volatile memorys,RRAM is considered to be the most likely to replace flash,due to its low power consumption,high speed,high ductility erase,long service life,CMOS compatibility and other advantages.Resistive memory was plagued by leakage current in large-scale integration,so 1D1R,1T1R,1S1R,CRS and other cell structures have been developed to suppress leakage current.Compared to the other structure,the 1D1R type RRAM is the earliest and most frequently reported,and has the advantages of simple structure,small unit size and easy integration etc,but there are little researches on the bending failure mechanism on it.In this work,the organic/inorganic heterojunction diode and conductive filament type resistance cell were constructed,and the influence of bending on the diode,resistance cell and 1D1R were investigated.The contents and conclusions are as followings:Firstly,use A1 and GaIn as electrodes,PFBT/ZnO as the organic/inorganic heterojunction,the effect of electrode(Au,Ag,Cu,Al),film structure,PMMA layers inserted were studied.The ideal factor and zero bias barrier height of the heterojunction were calculated,the diode rectification curve was linear fitted to analyze the transport mechanism,and the bending failure mechanism was studied by Abaqus.The results show that different types of top electrodes do not significantly change the rectifying characteristics,and can exclude the influence of electrode/functional layer interface.The heterojunction meets the thermal electron emission mechanism under forward bias,and the P-F effect is satisfied under negative bias.With the increase of the bending times,the negative bias voltage gradually transfers to the ohmic conduction,and the forward bias gradually shifts to the non ideal state.Secondly,take TiO₂ as the resistive medium and Al as the top electrode,the effect of different bottom electrodes(Al,Ag,Cu,ITO)on the resistive switching was studied.The results show that the on/off ratio of the device increases with the increase of the metal work function of the bottom electrode,and the electrode activity has a great influence on the stability of the device.For the Ag and Cu electrodes with high chemical activity,oxygen vacancies and metal conducting filaments can be formed simultaneously,the growth direction and shape of the filament an also affect the resistive switching.It was found that the stress of the TiO₂ film is obviously larger than electrode layers.Therefore,under the stress accumulation,after 3000 outer bending times,the crack may first occur in the TiO₂ layer and gradually spread to the electrode layers.Finally,use the diode and the resistive unit to form the 1D1R unit,the outer bending and inner bending were compared,it was found that the diode has better anti-bending ability.No matter in the outer bending or inner bending,the deterioration of the unidirectional switching of the 1D1R unit was prior to the resistive switching.After 600 bending times,because of the damage of ZnO,the diode degradates first;After 1000 bending times,the I-V curve transits to loop,the phenomenon of resistance change gradually disappears,microcrack has destroyed the growth of oxygen vacancy filaments.The 1D1R unit degenerated more seriously in the outer bending,the device was more sensitive to tensile stress than compressive stress,it was easy to cause crack,delamination,buckling and other failure forms.