A study of the leakage current in TiN/HfO2/TiN capacitors

Physical and electrical characteristics of Metal–Insulator–Metal TiN/HfO2/TiN capacitors have been investigated. A detailed study using internal photoemission and trap assisted transport simulation enabled the extraction of relevant important parameters like barrier height (2.5 eV) for both injecting interfaces, optical energy gap (5.6 eV), as well as trap density and energy position within the bandgap (NT = 3E19 cm-3; rT = 1E14 cm2; ET = 2.0–2.6 eV below the bottom of the HfO2 conduction band). The extracted parameters surprisingly showed striking similarities with HfO2 deposited on a Si surface, i.e., in MOSFET process flow. Additionally, Constant Voltage Stress showed a leakage current increase, preferentially at low voltage. This can be explained by preexisting defect precursors (likely related to oxygen vacancies) or by involvement of hydrogen in creating defects as observed on thermal SiO2 layers.