Deposition of thin films using an atmospheric pressure direct current plasma jet

Silicon-containing thin films are applied in various different fields, such as packaging, biomedical devices and optical components. Coatings deposited using plasma-enhanced chemical vapor deposition (PECVD) techniques attract many interests due to their economic and ecological advantages. Plasma deposited films are generally amorphous, insoluble, highly cross-linked, highly resistant to heat and corrosion and very adhesive to different substrates. Several atmospheric pressure plasma sources have been researched for thin film deposition. Compared to plasma sources that limit the plasma region between electrodes (inter-electrode distance: a few millimeters), plasma jets possess the characteristics of spatial separation between plasma region and processing region. Due to the fact that a DC discharge at atmospheric pressure inclines to transfer from a glow discharge to an arc, the DC plasma jet has attracted relatively little attention in the deposition of silicon-containing films. In this work, an atmospheric pressure direct current (DC) plasma jet for thin films deposition is investigated. By continual removal of heat from the active plasma region using a gas flow and by stabilizing the glow-to-arc transformation using ballast resistors, the atmospheric pressure DC plasma jet can work in a non-equilibrium state which is demonstrated from the gas temperature and the vibrational temperature of the nitrogen jet. The thin films are deposited using the plasma jet with tetramethyldisiloxane (TMDSO) as precursor. The effect of O2 flow and plasma discharge power on film deposition rate and film chemical characteristics is investigated in detail by surface profilometry, FTIR and XPS.