Depth resolved band alignments of ultrathin TiN/ZrO2 and TiN/ZrO2-Al2O3-ZrO2 dynamic random access memory capacitors

Abstract

In this paper, we investigated the interface band alignment of TiN/ZrO2 and TiN/ZrO2-Al2O3-ZrO2 (TiN/ZAZ) structures by analyzing the conduction band offset (CBO) and valence band offset at the electrode/dielectric interface using depth-resolved spectroscopy techniques. At the center of the interface, which is defined by the chemical composition depth profile, CBO values of 2.03 eV and 2.57 eV for ZrO2 and ZAZ were found, respectively. Subcutaneous TiON, which is induced by the process, was identified at this interface, and it played an important role in creating sub-band states. Based on combined analyses on both intrinsic and sub-band structures, a band alignment model is proposed. It was confirmed that the Al2O3 layer in ZAZ leads to a lowering of the Fermi energy or a p-doping effect, thereby increasing both the CBO and the tunneling barrier height in metal-insulator-metal capacitors.