Role of High-k Interlayer in ZrO2/High-k/ZrO2 Insulating Multilayer on Electrical Properties for DRAM Capacitor

Abstract

We studied characteristic of Metal-Insulator-Metal capacitors with ZrO2/high-k/ZrO2 (Z/high-k/Z)-nanolaminate dielectric layers and TiN electrodes. Amorphous Al2O3, (Ta/Nb)Ox (TN) and (Ta/Nb)Ox-Al2O3 (TNA) as high-k interlayer were prepared by atomic layer deposition and post-deposition annealing. The dielectric constant (k) of ZrO2 thin film exhibited about 28 because of tetragonal, orthorhombic and cubic phases. The k value of Z/high-k/Z-nanolaminate dielectric layer is high in order of ZTNZ > ZTNAZ > ZAZ due to the dependence of each k value of Al2O3 (~ 9) and TN (~29). The ZTNAZ layer exhibited lowest leakage current density of 10-8 ~ 10-7 A/cm2 at 0.6 V compared to those of ZAZ and ZTNZ in CET ~ 1.1 nm. We found that the leakage current property of Z/high-k/Z layer is influenced by not only amorphous structure but also band gap width (conduction band offset of ZrO2) of high-k interlayer. We conclude that the TNA material is one of the candidate material as high-k interlayer for future DRAM.