Selective photo-thermal modulation of ZnO/Pt interface for monolithic 3D integration of oxide-based resistive random access memory

Selective and localized process technology is a key enabler for the monolithic three-dimensional (M3D) integration of high-performance oxide-based resistive random access memory (RRAM) which is emerging as a post-flash nonvolatile memory solution. In this work, a photo-thermal laser process in a ZnO/Pt multi-layered structure is proposed as a new strategy to modulate the crystallinity at the ZnO/Pt interface and the oxygen vacancy (V_O) distribution in the ZnO layer. Intensive optical and thermal simulation has been utilized for the optimized laser processing of the ZnO/Pt interface. It is verified that the optimized laser process can produce a thin ZnO crystallized layer on the ZnO/Pt interface and a significant concentration gradient of V_O within the ZnO layer, without any deformation of the multi-layered structure. The switching characteristics of the laser-processed Pt/ZnO/Pt RRAM reveal that the laser process can increase the R_HRS/R_LRS ratio by up to tenfold and decrease the V_SET by about 25%. The reliability of the RRAMs is also considerably improved. Our research demonstrates that the photo-thermal approach is a very promising method for improving oxide-based RRAM performance while meeting the critical requirements of M3D integration.