AVS 53rd International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuP

Paper MN-TuP6
In Situ Characterization of Passivation Layer for Silicon Cryogenic Etching

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Aspects of MEMS and NEMS Poster Session
Presenter: C. Duluard, GREMI/CNRS - Université d'Orléans, France
Authors: X. Mellhaoui, GREMI/CNRS - Université d'Orléans, France
C. Duluard, GREMI/CNRS - Université d'Orléans, France
L. Pichon, GREMI/CNRS - Université d'Orléans, France
R. Dussart, GREMI/CNRS - Université d'Orléans, France
P. Ranson, GREMI/CNRS - Université d'Orléans, France
T. Tillocher, GREMI/CNRS - Université d'Orléans, France
P. Lefaucheux, GREMI/CNRS - Université d'Orléans, France
Correspondent: Click to Email
The cryogenic etching process that uses SF@sub 6@/O@sub 2@ plasma chemistry offers an attractive alternative to the Bosch process for etching high aspect ratio patterns into silicon, both for its high etch rate and its cleanliness. Today its use in industry is still limited primarily due to a need for more robustness, in particular a slight shift in temperature can affect the process reproducibility. Understanding the passivation mechanisms is therefore crucial to improve the passivation efficiency at low temperature and to control silicon deep etching perfectly. Previous studies have shown that a SiO@sub x@F@sub y@ passivation layer forms at low temperature and is removed when the substrate is heated back up to room temperature.@footnote 1@ Other experiments prove that this layer can also be constructed using a SiF@sub 4@/O@sub 2@ plasma, so sulphur does not seem to participate in the formation of a passivation layer.@footnote 2@ The thickness and physical-chemical properties of the passivation layer can only be known by in situ analyses. An inductively coupled plasma reactor was equipped with a spectroscopic ellipsometer to perform this characterization. In SF@sub 6@/O@sub 2@ etching plasma conditions the passivation layer is hardly observable. Nonetheless in SiF@sub 4@/O@sub 2@ chemistry a depositing regime can be achieved, which better facilitates ellipsometric measurements. Ellipsometric spectra were acquired and analyzed while varying several experimental parameters (e.g. plasma source power, substrate temperature). This parametric study will be presented. @FootnoteText@ @footnote 1@ R. Dussart, M. Boufnichel, G. Marcos, P. Lefaucheux, A. Basillais, R. Benoit, T. Tillocher, X. Mellhaoui, , H. Estrade-Szwarckopf, P. Ranson, J. Micromech. Microeng. 14, 190 (2004)@footnote 2@ X. Mellhaoui, R. Dussart, T. Tillocher, P. Lefaucheux, P. Ranson, M. Boufnichel, L. J. Overzet, J. Appl. Phys. 98, 104901 (2005)