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Synthesis and Characterization of Aerosol Silicon Nanoparticle Nonvolatile Floating Gate Memory Devices


Ostraat, Michele Louisa (2001) Synthesis and Characterization of Aerosol Silicon Nanoparticle Nonvolatile Floating Gate Memory Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/FDGV-GS71.


Silicon nanoparticle-based floating gate metal-oxide-semiconductor (MOS) field effect devices have potential for terabit cm-2 density nonvolatile memory applications. Aerosol synthesis of silicon nanoparticles is an important route toward the formation of discontinuous silicon nanoparticle floating gate structures that affords excellent control over particle size and size distribution, particle density, and oxide passivation. We have fabricated nanoparticle memory devices in a conventional MOS ultra-large scale integration (ULSI) process with channel lengths from 0.2 - 10 µm with a silicon nanoparticle floating gate fabricated by aerosol deposition.

SiO2 passivated silicon nanoparticles have been synthesized in an ultra clean two-stage aerosol reactor that is interfaced to a 200 mm wafer deposition chamber in a class 100 cleanroom. We synthesize silicon nanoparticles by thermal decomposition of silane gas at 950°C to produce single crystal, nonagglomerated nanoparticles. The second reactor stage passivated the silicon nanoparticles with a thin thermal oxide grown at 1050°C. Particles are thermophoretically deposited onto 200 mm silicon wafers with densities from 1013 particles cm-2 at the wafer center to 1011 particles cm-2 at the wafer edge in tens of minutes. We have fabricated floating gate memory devices in which the dielectric layer contains a discontinuous nanoparticle layer containing either (i) 2 -4 nm crystalline core diameter with 1 nm thermal oxide; or (ii) 6 - 15 nm crystalline core diameter with 2 nm thermal oxide. Cross-sectional transmission electron microscopy (TEM) verifies the presence of a silicon nanoparticle floating gate layer and planar TEM confirms nanoparticle morphology, size, and density.

Aerosol floating gate devices exhibit normal transistor behavior and have promising nonvolatile device performance. Aerosol nanoparticle devices with 0.2 mm channel lengths exhibit threshold voltages < 5 V with large threshold voltage shifts (~ 2 V), submicrosecond program times and millisecond erase times. No degradation in program/erase threshold voltage swing was observed during 105 program and erase cycles, although some threshold voltage shift due to charge trapping was observed. Electrostatic modeling indicates when a discontinuous nanoparticle layer can be modeled as a continuous sheet charge embedded within oxide and when it should be modeled as individual nanoparticles in an array.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:aerosol; electronic memory; nanocrystal; nanoparticle; nanoparticle memory; nanoparticle reactor; silicon
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Flagan, Richard C.
Thesis Committee:
  • Flagan, Richard C. (chair)
  • Atwater, Harry Albert
  • Gavalas, George R.
  • Seinfeld, John H.
Defense Date:6 February 2001
Record Number:CaltechETD:etd-04072005-081230
Persistent URL:
Ostraat, Michele Louisa0000-0003-2678-6171
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1285
Deposited By: Imported from ETD-db
Deposited On:07 Apr 2005
Last Modified:29 Nov 2022 23:08

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