University of California

Los Alamos National Security, LLC

Steve E Babayan

Gary S Selwyn

Robert F Hicks

Ivars Henins

Large area atmospheric-pressure plasma jet. A plasma discharge that can be operated at atmospheric pressure and near room temperature using 13.56 MHz rf power is described. Unlike plasma torches, the discharge produces a gas-phase effluent no hotter than 250&deg; C. at an applied power of about 300 W, and shows distinct non-thermal characteristics. In the simplest design, two planar, parallel electrodes are employed to generate a plasma in the volume therebetween. A &ldquo;jet&rdquo; of long-lived metastable and reactive species that are capable of rapidly cleaning or etching metals and other materials is generated which extends up to 8 in. beyond the open end of the electrodes. Films and coatings may also be removed by these species. Arcing is prevented in the apparatus by using gas mixtures containing He, which limits ionization, by using high flow velocities, and by properly spacing the rf-powered electrode. Because of the atmospheric pressure operation, there is a negligible density of ions surviving for a sufficiently long distance beyond the active plasma discharge to bombard a workpiece, unlike the situation for low-pressure plasma sources and conventional plasma processing methods.

Large area atmospheric-pressure plasma jet

Deposition of coatings using an atmospheric pressure plasma jet. The use of a nonthermal source which is capable of operation at 760 torr is demonstrated. As an example of the application of the present invention, a helium/oxygen gas mixture is introduced into the annular region between two coaxial electrodes driven by a 13.56 MHz radio frequency (rf) source at between 40 and 500 W to produce a stable plasma jet. Silicon dioxide films are deposited by introducing tetraethoxysilane (TEOS) into the effluent stream. A deposition rate of 3020&plusmn;250 &angst;/min. is achieved with an rf power of 400 W, 0.2 torr of TEOS, 11.1 torr of oxygen, 748.7 torr of helium, and a total gas flow rate of 41 L/min. The deposition rate depends on the oxygen partial pressure, the TEOS partial pressure, and the rf power to the 0.28, 0.47, and 1.41 powers, respectively. However, increasing the temperature decreases the deposition rate. The observed dielectric constants of the films decrease from 5.0&plusmn;0.2 to 3.81&plusmn;0.03 as the deposition temperature increases from 115 to 350&deg; C. Infrared spectra of the deposited films at 350&deg; C. show no carbon or hydroxyl ion contamination, indicating excellent material purity.

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Huntington Beach, CA, United States of America

Steve E Babayan