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

We studied characteristic of Metal-Insulator-Metal capacitors with ZrO 2 /high- k /ZrO 2 (Z/high- k /Z)-nanolaminate dielectric layers and TiN electrodes. Amorphous Al 2 O 3 , (Ta/Nb)O x (TN) and (Ta/Nb)O x -Al 2 O 3 (TNA) as high- k interlayer were prepared by atomic layer deposition and post-deposition annealing. The dielectric constant ( k ) of ZrO 2 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 Al 2 O 3 (~ 9) and TN (~29). The ZTNAZ layer exhibited lowest leakage current density of 10 -8 ~ 10 -7 A/cm 2 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 ZrO 2 ) of high- k interlayer. We conclude that the TNA material is one of the candidate material as high- k interlayer for future DRAM.