Effects of CF4 Addition on the Growth of Amorphous CNx Films by Plasma Decomposition of CH4-N2 Gas Mixtures

Abstract

ABSTRACTHydrogenated amorphous carbon nitride (α-CNx:H) films are deposited at 50–300°C by radio-frequency plasma decomposition of CH4-CF4-N2 gas mixtures. Effects of fluorine radicals on the deposition rate, composition, and on chemical bonding are investigated. When CF4 gas is added as partial replacement of CH4 gas, the deposition rate at 200°C steeply increases with increasing flow rate ratio RCF = [CF4]/([CH4]+[CF4]) up to ∼0.3, and then it decreases gradually. It is found that the nitrogen content, x, increases from 0.22 to 0.46 when RCF increases from 0 to 0.75. The inclusion of fluorine atoms into the films is less than 5 at%. The infrared absorption spectra shows strong enhancement of the absorption bands related to various forms of C—N bonding by the CF4 addition. It is found that the addition of CF4enhances the formation of C–N bonds in PECVD α-CNx:H films.