AVS 57th International Symposium & Exhibition
    MEMS and NEMS Thursday Sessions
       Session MN-ThM

Paper MN-ThM11
Fabrication of High Density Single Crystal Silicon Nanowires for Ensemble Measurements

Thursday, October 21, 2010, 11:20 am, Room Santo Domingo

Session: Multi-scale Interactions of Materials at the Micro- and Nano-scale
Presenter: D.A. Czaplewski, Argonne National Laboratory
Authors: D.A. Czaplewski, Argonne National Laboratory
L.E. Ocola, Argonne National Laboratory
M.V. Holt, Argonne National Laboratory
Correspondent: Click to Email
Silicon nanowires have shown promise in applications such as photovoltaic cells, lithium storage for batteries, transducers, sensors, and many more. Single crystal silicon nanowires (SCSN) have been used to study materials and electrical properties of Si as the nanowires have been scaled down towards several nanometers. These experiments have been designed to test the classical predictions of materials behavior as the assumption of continuum mechanics starts to break down. Due to the small sizes of SCSNs, measurements of materials properties have been inconsistent due to the variation in dimensions and fabrication methods from wire to wire. Typically, SCSNs are fabricated at very low densities, which make measurements of ensembles very difficult. Here we present two top-down processes to create SCSNs at relative densities approaching 50% of a continuous film with dimensions as small as 30 nm. Both fabrication processes start with e-beam lithography. In the first fabrication process, a positive e-beam resist is patterned and developed. The resist is exposed to a second dose of electrons to increase the etch selectivity during reactive ion etching. The silicon structures are reactive ion etched in a CHF3-O2 plasma chemistry to define the structures. In the second approach, a negative e-beam resist, hydrogen silsesquioxane (HSQ), is patterned and developed on a thin thermally-cured HSQ layer. After development, the pattern is transferred into the silicon via a reactive ion etch using a Chlorine chemistry followed by a HBr-O2 chemistry. After the wires are defined, they are subsequently released in a dilute HF-DI water mixture and then dried using a super critical CO2 drying technique. The released structures are being used for studies of coupled mechanical oscillators and to study materials and electrical properties in ensembles of 1-D wires.