The Contrasting Impacts of the Al2O3 and Y2O3 Insertion Layers on the Crystallization of ZrO2 Films for Dynamic Random Access Memory Capacitors

Abstract

This study examines the influences of the Al2O3 and Y2O3 insertion layers (ILs) on the structural and electrical features of ZrO2 thin films for their application to dynamic random access memory capacitors. The ultra-thin Al2O3 IL (0.1-0.2 nm) dissolves into the ZrO2 layers, which causes the top and bottom portions of the ZrO2 film to merge and have smaller lattice parameters. However, the thicker Al2O3 IL (>approximate to 0.4 nm) forms a continuous layer and separates the top and bottom portions of the ZrO2 film. Interestingly, the diffusion of Al does not occur in this case. Overall, the dielectric constant (kappa) of the ZrO2/Al2O3/ZrO2 film is lower than that of the undoped ZrO2 film due to the involvement of the low-kappa Al2O3 IL. In contrast, the Y2O3 IL does not interfere with the grain growth of ZrO2, rendering the continuous ZrO2 grain formation throughout the entire film thickness despite the presence of the continuous region with a higher Y-concentration. The most crucial finding is that the Y-doping significantly decreases the leakage current without sacrificing the dielectric constant. This leakage current decrease can be ascribed to the p-type doping effect of Y ions in the n-type ZrO2.