Silicon-germanium self-assembled quantum dot growth and applications in nanodevices.

摘要

To achieve further scaling down of MOSFETs, single-electron devices utilizing the Coulomb blockade effect will likely be the basic element of future solid-state electronics. Silicon or SiGe quantum dots embedded in an insulator have potential application for room temperature operation of single-electron transistor and nonvolatile memory devices.; In first study, direct growth of Ge dots on insulators, such as nitrided oxides, which are suitable for tunneling oxides (3nm) in memory devices were achieved. Germanium dots were grown at different temperatures on various dielectric substrates, including Si₃N₄, SiO₂, oxynitride, NH₃-annealed oxynitride, NH₃-annealed nitride, and N ₂O-annealed nitrided oxide.; In second study, SiGe quantum dot growth between 500°C and 525°C using a Si₂H₆/GeH₄/H₂ based chemistry was studied. For dielectrics, both SiO₂ and hafnium oxide (HfO ₂), high-K gate dielectric which uses thicker layer for reduced leakage, improved resistance to boron diffusion, and better reliability characteristics were used. The growth of SiGe dots is limited by the GeH₄ partial pressure, which determines the activation energy of disilane decomposition in the surface-reaction-limited regime and the number of hydrogen desorption sites on the substrate.; Finally, a SiGe dot floating-gate flash memory with HfO₂ tunneling oxide was developed. Using SiGe dots and HfO₂ tunneling oxide, which allows for a thicker physical oxide thickness than an equivalent SiO ₂ tunneling oxide without sacrificing non-volatility, a low program/erase voltage as well as good endurance and charge retention characteristics can be achieved. (Abstract shortened by UMI.)