The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Atomistic Modelling of Anisotropic Etching of Crystalline Silicon

Miguel A. Gosálvez

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Engineering Physics and Mathematics for public examination and debate in Council Room H304 at Helsinki University of Technology (Espoo, Finland) on the 19th of September, 2003, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-6707-1)   [9219 KB]
Dissertation is also available in print (ISBN 951-22-6706-3)

Abstract

An atomistic model for the simulation of anisotropic wet chemical etching of crystalline silicon is developed. Special attention is paid to the relation between the atomistic processes, the mesoscopic features of the surface morphology and the macroscopic anisotropy of the process, bridging the different length scales.

The development of the atomistic model is made by direct comparison of atomistic kinetic Monte Carlo and Cellular Automaton simulations with experimental results, guided by first-principles calculations. The model explains the anisotropy of the etching process and the orientation-dependent surface morphology as two different manifestations of the same atomistic mechanisms, namely, the weakening of backbonds following OH termination of surface atoms and the existence of significant interaction between the terminating species (H / OH). The versatility of the atomistic model is demonstrated by the concentration and time dependence of the simulated under-etched structures and surface morphology.

A substantial effort has been made to develop an efficient program in order to simulate the etching process in arbitrarily oriented, large, micrometer-scale systems in the presence (or absence) of masking patterns and considering the effects of temperature and etchant concentration. The program has a great potential for use in the optimization of the processing parameters in industrial applications.

This thesis consists of an overview and of the following 6 publications:

  1. Gosálvez M. A., Nieminen R. M., Kilpinen P., Haimi E. and Lindroos V., 2001. Anisotropic wet chemical etching of crystalline silicon: atomistic Monte-Carlo simulations and experiments. Applied Surface Science 178, No. 1-4, pages 7-26. © 2001 Elsevier Science. By permission.
  2. Gosálvez M. A., Foster A. S. and Nieminen R. M., 2002. Multiscale modeling of anisotropic wet chemical etching of crystalline silicon. Europhysics Letters 60, No. 3, pages 467-473. © 2002 EDP Sciences. By permission.
  3. Gosálvez M. A., Foster A. S. and Nieminen R. M., 2002. Atomistic simulations of surface coverage effects in anisotropic wet chemical etching of crystalline silicon. Applied Surface Science 202, No. 3-4, pages 160-182. © 2002 Elsevier Science. By permission.
  4. Gosálvez M. A., Foster A. S. and Nieminen R. M., 2003. Dependence of the anisotropy of wet chemical etching of silicon on the amount of surface coverage by OH radicals. Sensors and Materials 15, No. 2, pages 53-65.
  5. Gosálvez M. A. and Nieminen R. M., 2003. Surface morphology during anisotropic wet chemical etching of crystalline silicon. New Journal of Physics 5, pages 100.1-100.28. © 2003 Institute of Physics Publishing Ltd. By permission.
  6. Gosálvez M. A. and Nieminen R. M., 2003. Relation between macroscopic and microscopic activation energies in non-equilibrium surface processing. Physical Review E, in press. © 2003 by authors and © 2003 American Physical Society. By permission.

Keywords: anisotropic wet chemical etching, surface morphology, Monte Carlo, cellular automaton, mask, convex corner, crystalline silicon, activation energy, surface processing

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© 2003 Helsinki University of Technology

Last update 2011-05-26