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Abstract

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.+-.250 .ANG./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.+-.0.2 to 3.81.+-.0.03 as the deposition temperature increases from 115 to 350.degree. C. Infrared spectra of the deposited films at 350.degree. C. show no carbon or hydroxyl ion contamination, indicating excellent material purity.

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