J. Aerosol Sci., Vol. 24, No. 5, pp. 687-690, 1993 0021 8502/93 $6.00 + 0.00 Printed in Great Britain. Pergamon Press Ltd TECHNICAL NOTE Deposition of Ultrafine Particles on Semiconductors for Use as Dry Etching Masks: Numerical Calculation and Experimental Verification F. Stratmann 1, A. Wiedensohler 2, I. Maodmov3, L. Samuelson 3, H.C. Hansson 2, H.J. Fissan 1 1 Process- and Aerosol Measurement Technology, University of Duisburg, Bismarckstr. 90, 4100 Duisburg 1, Germany. 2 Department of Nuclear Physics, University of Lund, SSlvegatan 14, S-223 62 Lund, Sweden. 3 Department of Solid State Physics, University of Lund, Box 118, S-221 00 Lund, Sweden. Keywords: quantum dots, ultrafine particles, particle deposition INTRODUCTION There is a considerable interest in new fabrication methods of quantum dot (QD) semiconductor structures to use as active parts in, e.g. semiconductor lasers. Recently we proposed a novel technology for large scale fabrication of QD structures which utilizes aerosol particle deposition and plasma etching techniques (Wiedensohler et al., 1992). For such application it is important to be able to control the particle deposition onto a semiconductor surface. Considering aerosol flow across a fiat surface and accounting for particle transport due to combined convection, diffusion and electrostatic forces, the deposition results are obtained using the extended 2-D SIMPLER-Algorithm (Stratmann and Whitby, 1989) to solve for the occuring fiuidmechanical and aerosol dynamical effects. Ultrafine monodisperse silver particles are produced in a size range below 50 nm in diameter using a tube furnace generator and deposited on semiconductors in a particle deposition chamber. The particle concentrations on the semiconductor surfaces are determined with a Scanning Electron Microscope (SEM). Theoretical and experimental results are presented showing the effects of particle size and electrical field strength on particle deposition and particle deposition profiles. GOVERNING EQUATIONS Assuming steady state and incompressible flow with constant material properties the governing equations (continuity-, Navier-Stokes-, convective-diffusion- and fourth Maxwellian-Equation) can be written as follows: v.z=o (1) v. (p~z) = -vp- v.~ (2) v. (~n) = DV2n - V . (~*~ln) (3) V. ~ = 0 (4) where z7 is the gas velocity, p the gas density, p the pressure, 7- the stress tensor, n the particle number concentration, D the particle diffusion coefficient, gel the relative particle velocity due to the electrical field and/~ is the electrical field strength. In eq. 3 particle transport due to combined convection, diffusion and electrostatic forces is accounted for. The description of the particle transport in the investigated deposition chamber (fig. 2) represents a truely 3-dimensional problem. Nevertheless, usefull informations about the particle flux to the 687