Particle precipitation in connection with KOH etching of silicon

Christian Bergenstof Nielsen, Carsten Christensen, Casper Pedersen, Erik Vilain Thomsen

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    This paper considers the precipitation of iron oxide particles in connection with the KOH etching of cavities in silicon wafers. The findings presented in this paper suggest that the source to the particles is the KOH pellets used for making the etching solution. Experiments show that the precipitation is independent of KOH etching time, but that the amount of deposited material varies with dopant type and dopant concentration. The experiments also suggest that the precipitation occurs when the silicon wafers are removed from the KOH etching solution and not during the etching procedure. When not removed, the iron oxide particles cause etch pits on the Si surface when later processed and exposed to phosphoric acid. It has been found that the particles can be removed in an HCl solution, but not completely in an H2SO4- H2O2 solution. The paper discusses the involved precipitation mechanism in terms of the change in free energy of adsorption, the Pourbaix diagram, the electrochemical double- layer thickness and silicon dopant type, and concentration. (C) 2004 The Electrochemical Society.
    Original languageEnglish
    JournalJournal of The Electrochemical Society
    Issue number5
    Pages (from-to)G338-G342
    Publication statusPublished - 2004

    Bibliographical note

    Copyright The Electrochemical Society, Inc. [2004]. All rights reserved. Except as provided under U.S. copyright law, this work may not be reproduced, resold, distributed, or modified without the express permission of The Electrochemical Society (ECS).


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