Modeling of Silicon Nanodots Nucleation and Growth Deposited by LPCVD on SiO2 : From Molecule/Surface Interactions to Re
- PDF / 407,995 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 46 Downloads / 145 Views
0959-M17-12
Modeling of Silicon Nanodots Nucleation and Growth Deposited by LPCVD on SiO2 : From Molecule/Surface Interactions to Reactor Scale Simulations Ilyes Zahi1,2, Hugues Vergnes2, Brigitte Caussat2, Alain Esteve1, Mehdi Djafari Rouhani1, Pierre Mur3, Philippe Blaise3, and Emmanuel Scheid1 1 Laboratoire d’Analyse et d’Architecture des Systèmes, UPR-CNRS 8011, 7, av du Colonel Roche, Toulouse, 31077, France 2 Laboratoire de Génie Chimique, ENSIACET, Institut National Polytechnique de Toulouse,UMR-CNRS 5503, 5 rue Paulin Talabot, Toulouse, 31106, France 3 CEA-LETI-MINATEC, 17 avenue des Martyrs, Grenoble, 38054, France
ABSTRACT We present first results combining models at continuum and atomistic (DFT, Density Functional Theory) levels to improve understanding of key mechanisms involved in silicon nanodots (NDs) synthesis on SiO2 silicon dioxide surface, by Low Pressure Chemical Vapor Deposition (LPCVD) from silane SiH4. In particular, by simulating an industrial LPCVD reactor using the CFD (Computational Fluid Dynamics) code Fluent, we find that deposition time could be increased and then reproducibility and uniformity of NDs deposition could be improved by highly diluting silane in a carrier gas. A consequence of this high dilution seems to be that the contribution to deposition of unsaturated species such as silylene SiH2 highly increases. This result is important since our first DFT calculations have shown that silicon chemisorption on silanol Si-OH or siloxane Si-O-Si bonds present on SiO2 substrates could only proceed from silylene (and probably from other unsaturated species). The silane saturated molecule could only contribute to NDs growth, i.e. silicon chemisorption on already deposited silicon bonds. Increasing silylene contribution to deposition in highly diluting silane could then also exalt silicon nucleation on SiO2 substrates and then increase NDs density. INTRODUCTION The need of high integrated systems (PC, car, MP3, mobile …) of the everyday life involves a permanent evolution of the microelectronic industry. Non volatile Flash memory is a good example of these trends. The poly-silicon floating gate technology of the Flash memories could be replaced, in a near future, by a discrete trap floating gate technology in which discrete traps are made up of silicon nanodots (NDs)1,2. The deposition of NDs by Low Pressure Chemical Vapor Deposition (LPCVD) from silane SiH4 on SiO2 surfaces remains one of the most promising ways of synthesis. Nevertheless, it is mandatory to reach an area density of at least 1012 NDs/cm2 and NDs radii lower than 5 nm to industrialize convenient and reliable Flash memories. Despite a huge experimental effort to reach such density and size targets, fundamental understanding of the key mechanisms of NDs nucleation and growth remains elusive. In particular, NDs deposition in industrial LPCVD reactors involves run durations as low as 10 s. In such conditions, it has been observed that this step has not a convenient reproducibility and in addition NDs are not deposited unifo
Data Loading...
