AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS1-ThM

Invited Paper PS1-ThM3
Deposition of Transparent Tin Oxide Films by PECVD on Polymers

Thursday, November 6, 2003, 9:00 am, Room 314

Session: Plasma-Surface Interactions: Deposition
Presenter: F. Arefi-Khonsari, Laboratoire de Genie des Procedes Plasma et Traitement de Surface ENSCP, France
Authors: F. Arefi-Khonsari, Laboratoire de Genie des Procedes Plasma et Traitement de Surface ENSCP, France
J. Pulpytel, Laboratoire de Genie des Procedes Plasma et Traitement de Surface ENSCP, France
H. Cachet, UPR15-CNRS, France
Correspondent: Click to Email
Transparent conductive tin oxide films have been deposited at low temperature(< 50°C) from a mixture of O@2sub@/Ar/TMT on two substrates for two different applications : 1) biofouling reduction for underwater instrumentation on polymer windows and 2)as sensitive layers of gas microsensors on silicon wafers. In order to obtain carbon free tin oxide films, mass spectrometry was performed by using a calibration mixture composed of inert gases. The latter allowed us to determine the molar fraction of the stable species produced in the discharge, such as CO & CO@2sub@ namely those which witness the carbon etching of the organometallic precursor. For this study the role of the two major parameters i.e. power and oxygen partial pressure in the reactor have been studied. The biofouling reduction was based on seawater electrolysis at the optical surface for producing active chlorine species. In order to limit the ageing effect of tin oxide films deposited on polymers, they were doped with fluorine atoms which gave rise to higher conductivities and limited also the ageing effect. Precursors such as SF@6sub@ and C@4sub@F@6sub@ were introduced in the plasma mixture in order to dope the tin oxide films in a one step process. In the case of SF@6sub@, an increase of the electrical conductivity and charge carriers were obtained for very small flow rates of SF@6sub@ introduced in the discharge. For higher flow rates, a sharp decrease of the conductivity was observed. For such flow rates, competitive etching and functionalization processes, assisted by fluorine atoms present in the discharge, took place giving rise to a sharp decrease of the deposition rate and the incorporation of Sn-F and C-F bonds in the deposited films. This has been explained by the formation of new species such as S O@2sub@, SOF, SOF@2sub@ and HF. Oxygen being consumed to form such species, it is much less involved in forming CO, CO@2sub@ and H@2sub@O species, therefore leading to the incorporation of carbon species in the deposit which explains the sharp decrease of the conductivity of the films.