Chemical Etch Rate and X-Ray Structure of Reactive Sputtered c-Axis Aligned Crystalline InxGayZnzO4 Films

Abstract

This paper examines the correlation between deposition parameters and crystallinity, texture, and etch rate of reactively sputtered c-axis aligned crystalline (CAAC) IGZO films. Both X-ray diffraction and general area detector diffraction (GADDS) showed that crystallinity increases rapidly above 200°C with simultaneous formation of highly aligned CAAC. Optimal texture with a c-axis alignment and a minimum GADDS full-width-at-half-maximum of 18° occurred at 250°C, with c-axis alignment decreasing at higher temperatures to a FWHM of 35° at 385°C. Chemical etch rate in 5 vol% HCl was highly correlated to crystallinity, dropping by a factor of ten in CAAC compared to amorphous IGZO; etch rate hence provides a highly sensitive measure of crystallinity.