Single- and Dual-Layer Nanocrystalline Indium Tin Oxide Embedded ZrHfO High-k Films for Nonvolatile Memories – Material and Electrical Properties

Abstract

MOS capacitors composed of singe- and dual-layer nc-ITO embedded ZrHfO high-k gate dielectric stacks were fabricated and characterized for nonvolatile memory functions. Detailed material and electrical properties such as charge-trapping and -detrapping characteristics have been investigated. The XPS analysis indicates the formation of an interface layer at the nc-ITO and ZrHfO contact region. The memory function of this kind of device is mainly based on trapping holes at both bulk nc-ITO sites and nc-ITO/ZrHfO interfaces. By including the second nc-ITO layer into the nc-ITO embedded high-k dielectric stack, the capacitor showed a larger hole-trapping density, a higher data-programming efficiency, and a longer charge retention time. The frequency-dependent capacitance-voltage and conductance-voltage measurement results showed that part of the trapped holes were loosely retained at the nc-ITO/ZrHfO interface. These loosely-trapped holes are responsible for the peak formation in the J-V curve. The long life of the nc-ITO embedded ZrHfO sample makes it suitable for the future nonvolatile memories. © 2011 The Electrochemical Society.