Sputter rate measurements of Cu(In,Ga)Se2 absorber layers with varied Ga ratios, primary voltage, and angle of incidence by secondary ion mass spectrometry

Abstract

Thin film Cu(In,Ga)Se 2 (CIGS) layers were deposited by a 1-stage and 3-stage coevaporation process on Mo/Glass substrates at various Ga/(Ga+In) ratios (Ga ratio). The sputter rate and the depth profile of 1-stage CIGS absorber layers at various Ga ratios were measured using secondary ion mass spectrometry (SIMS) using different primary voltages and angles of incidence of a Cs beam in order to study how the Ga ratio of CIGS affected the sputter rate. It was determined that there was up to 50% variation in film sputter rate depending on the Ga ratio range, SIMS primary voltage, and angle of incidence. A point-by-point correction method was then developed to correct for relative sputter rate differences in 3-stage CIGS samples with a graded Ga ratio profile.