High dielectric constant gate oxides for III-V CMOS.

摘要

III-V compound semiconductors are of interest as channel materials for next-generation metal-oxide-semiconductor field effect transistors (MOSFETs), as silicon devices reach their fundamental materials limitations. The high electron mobilities of III-V semiconductors potentially allow for higher saturation velocities and further performance scaling. High dielectric constant ( k) gate oxides are essential for MOSFET devices and are a major challenge in developing III-V MOSFETs. Interfaces between dielectrics and III-V semiconductors exhibit extremely large interface trap densities, which degrade the transistor performance. Quantitative methods are required to estimate the interface electrical properties and to optimize the interfaces. Methods developed for Si interfaces cannot directly be applied because of differences in the band structures.;In this dissertation, high-k gate dielectric deposition and quantitative interface analysis are developed, focusing on MOS capacitors (MOSCAPs) with In0.53Ga0.47As channels. By employing a ultra-high vacuum chemical beam deposition technique using alkoxide precursors, TiO2, ZrO2, and HfO2 gate dielectrics are developed. Their potentials and limitations as gate dielectrics for In 0.53Ga0.47As MOSFET are discussed. It is shown that growth modes and electrical properties are significantly improved by introducing an alkyl precursor (trimethylaluminium). MOSCAPs showing a 1 nm equivalent oxide thickness (EOT) and a relatively low interface trap density of 10 12 eV-1cm -2 are demonstrated with HfO2 dielectrics. Capacitance-based and conductance-based methods are developed for characterizing the interface trap density of In0.53 Ga0.47As MOSCAPs and guidelines are introduced to assess the electrical quality of high-k gate oxide/III-V interface.