Dry patterning of copper films using an O 2 plasma and hexafluoroacetylacetone

Abstract

Dry etching of copper films using O 2 plasmas and H(hfac) has been investigated. A one-step process consisting of copper film oxidation with an O 2 plasma and removal of surface copper oxide by reaction with H(hfac) to form volatile Cu(hfac) 2 and H 2O was carried out. The etching rate of Cu was in the 50–700 Å/min range at the substrate temperature from 150 to 300°C and depended on the H(hfac)/O 2 flow rate ratio and the plasma power. The copper film etch rate increased with increasing radio frequency (RF) power at temperatures higher than 215°C. The optimum H(hfac)/O 2 flow rate ratio was 1:1, suggesting that the oxidation process and the reaction with H(hfac) should be in balance. Cu patterning using a Ti mask was performed at a flow rate ratio of 1:1 at 250°C and an isotropic etching profile with a taper slope of 30° was obtained. Cu dry patterning with a taper angle necessary for high-resolution large-area thin film transistor liquid-crystal displays was thus successfully obtained from the one-step process by manipulating the substrate temperature, RF power and flow rate ratio.