Controlled Microwave Processing of IGZO Thin Films for Improved Optical and Electrical Properties

Abstract

Amorphous indium gallium zinc oxides (IGZO) of 100 nm thickness were deposited onto glass substrates by sputtering at room temperature. The films were subsequently annealed in air, vacuum, forming gas and O2 environments by both conventional and microwave methods. The optical and electrical properties of the as-deposited and annealed samples were measured and compared. It was seen that microwave annealing had a dual advantage of reduced time and lower temperature compared to conventional annealing. The optical and electrical properties of the IGZO thin films were measured by UV–Visible spectrophotometry, Hall measurement and four-point probe analyses, respectively. On microwave anneals of 4 min at 200°C, the resistivity of IGZO thin films was lowered to 4.45 and 4.24 × 10−3 Ω-cm in vacuum and forming gas, respectively. However in conventional annealing at 400°C, it took 24 h to reach 4.5 and 4.2 × 10−3 Ω-cm in vacuum and forming gas, respectively. The average transmittance of IGZO improved from 80% to almost 86% for microwave annealing.