Etching of Copper Films for Thin Film Transistor Liquid Crystal Display using Inductively Coupled Chlorine-Based Plasmas

Abstract

In this study, using inductively coupled Cl2/Ar plasmas (ICP), the effects of various process conditions such as source power, bias power, Cl2/Ar gas ratio, and ultraviolet (UV) ray were investigated to obtain high Cu etch rates without remaining any nonvolatile etch products. Due to the formation of nonvolatile copper chloride, copper film was not etched and, instead, a thick copper chloride residue was formed on the copper surface when Cl2/Ar ICP plasma was used. However, the residue could be removed and the copper film could be etched when high ICP source power was used with high intensity of ultraviolet rays and high bias power. Especially, when the ICP source power higher than 300 W and the bias power higher than 70 W were used, no UV irradiation was required to etch copper films, and which is more desirable for the etching of thin film transistor liquid crystal display (TFT-LCD) substrates. The maximum copper etch rate obtained was 300 nm/min with inductive power of 600 W, bias power of 75 W, and 0.5 of Cl2/Ar gas ratio at the pressure of 7 mTorr without applying UV.