Reaction characteristics between Cu thin film and RF inductively coupled Cl-2 plasma without/with UV irradiation

Abstract

Reaction characteristics between copper (Cu) thin film and inductively coupled Cl-2 plasma at room temperature have been studied over a pressure range of 2 - 20 mTorr, an RF inductive power range of 300 - 700 W, a Cl-2 Bow range of 5 - 30 seem and a substrate bias range from 0V to -60 V. The main reaction product was a substoichiometric CuClx(s) layer, and it was found that the chlorine concentration "x" and the formation rate of the CuClx(s) layer were greatly influenced by RF power, dilution gases (N-2 or Ar), pressure and Cl-2 flow rate. The effect of negative substrate bias was found to enhance the formation rate of CuClx(s) linearly such that the total copper etch rate was increased, while the chlorine concentration "x" was unaffected. It was found that the copper consumption rate for the entire Cu etch reaction was enhanced by UV irradiation by approximately five times. The chloride layer formed upon UV irradiation was found to have a much higher Cl concentration (x > 1.0) in CuClx compared to the much lower Cl concentration without UV irradiation, and to be composed of the CuCl2(s) phase and CuCl1(s) phase.