High-density plasma etching characteristics of indium-gallium-zinc oxide thin films in CF4/Ar plasma

Abstract

We investigated the etching process of indium-gallium-zinc oxide (IGZO) thin films in an inductively coupled plasma system. The dry etching characteristics of the IGZO thin films were studied by varying the CF4/Ar gas mixing ratio, RF power, DC-bias voltage, and process pressure. We determined the following optimized process conditions: an RF power of 700W, a DC-bias voltage of -150 V, and a process pressure of 2 Pa. A maximum etch rate of 25.63 nm/min for the IGZO thin films was achieved in a plasma with CF4/Ar(= 25: 75), and the selectivity of IGZO to Al and TiN was found to be 1.3 and 0.7, respectively. We determined the ionic composition of the CF4/Ar plasma using optical emission spectroscopy. Analysis of chemical reactions at the IGZO thin film surfaces was performed using X-ray photoelectron spectroscopy. (C) 2015 Elsevier B.V. All rights reserved.