Study of in Situ Silver Migration in Amorphous Boron Nitride CBRAM Device

Abstract

We report the dependence of the thickness of amorphous boron nitride (a-BN) on the characteristics of conductive bridge random access memory (CBRAM) structured with the Ag/a-BN/Pt stacking sequence. The a-BN thin film layers of three different thicknesses of 5.5, 11, and 21.5 nm were prepared by the sputtering deposition. Depending on the thickness of the a-BN layer, the devices are found to be in either low-resistance state (LRS) or high-resistance state (HRS) prior to any consecutive switching cycle. All devices with 5.5 nm thick a-BN switching layer are in LRS as the pristine state, while devices with 21.5 nm thick a-BN layer are found to be in HRS as the pristine state. To attain reliable switching cycles, initial RESET and electroforming process are necessarily required for the devices with 5.5 and 21.5 nm thick a-BN layer, respectively. However, the devices with the a-BN layer of thickness between 5.5 and 21.5 nm in pristine states are in either HRS or LRS. This dependence of the a-BN thickness on different resistance states in the pristine state can be explained by in situ Ag diffusion during its sputter deposition to form a top electrode on the a-BN layer. Our finding shows a detailed investigation and a deep understanding of the switching mechanism of Ag/a-BN/Pt CBRAM devices with respect to different a-BN thicknesses for the future computing system.