AVS 61st International Symposium & Exhibition
    Advanced Surface Engineering Monday Sessions
       Session SE+EM+EN+PS+TF-MoM

Paper SE+EM+EN+PS+TF-MoM2
Real Time Characterization of Polymer Surface Modification by an Atmospheric Pressure Plasma Jet

Monday, November 10, 2014, 8:40 am, Room 302

Session: New Developments in Atmospheric Pressure Plasma Deposition and Thin Films for Energy Applications
Presenter: Andrew Knoll, University of Maryland, College Park
Authors: A.J. Knoll, University of Maryland, College Park
P. Luan, University of Maryland, College Park
E.A.J. Bartis, University of Maryland, College Park
C. Hart, University of Maryland, College Park
Y. Raitses, Princeton Plasma Physics Laboratory
G.S. Oehrlein, University of Maryland, College Park
Correspondent: Click to Email
Atmospheric pressure plasma jets (APPJ) have been shown to modify surfaces, leading to a variety of potential industrial and medical applications. APPJ treated surfaces are typically evaluated post treatment, but few studies exist showing surface changes in real time. In this study, we characterized both closely-coupled and remote APPJ treatments of a PMMA-based 193 nm photoresist polymer (PR193) using in situ ellipsometry to monitor film thickness and refractive index in real time. The kilohertz-driven, two-ring electrode APPJ was fed with low admixtures of O2 and N2 to Ar. Voltage and current waveforms were collected to electrically characterize the APPJ and measure power dissipation. In addition, high speed photography of the APPJ was conducted in order to characterize plasma interaction with various controlled environments and with PR193. Ellipsometry shows that PR193 etch rates depend on the feed gas chemistry and treatment time. Etch rates are reduced for Ar/O2 compared with pure Ar and Ar/N2. This reduction is correlated to a decrease in plasma density with O2 addition. It is also shown that the etch rate changes over time initially during APPJ heating and reaches steady state as the temperature stabilizes. When the plasma is brought close enough to the sample, the discharge couples with the surface and arcing to the film occurs. This interaction greatly increases the etch rate and introduces major damage to the polymer, which can be observed by the naked eye. From electrical data and high speed photography we see that the pure Ar discharge exhibits filamentary behavior that is enhanced by O2 addition and rendered more diffuse by N2 addition. High speed photography shows that the coupling of the plasma and the environment increases when the environment matches the feed gas chemistry, which causes the plume to extend farther than in open air. While the Ar plume is confined to a single plasma channel, N2 admixture to Ar branches out into many smaller discharges, similar to a Lichtenberg figure. We also correlate damage seen on the polymer surface with observed arcing. The authors gratefully acknowledge financial support by US Department of Energy (DE-SC0001939).