Electrical Properties Engineering of Sputtered Indium Gallium Zinc Oxide Semiconductor Thin Films

Abstract

The influence of deposition conditions and laser annealing on the electrical properties of indium gallium zinc oxide (IGZO) semiconducting thin films was investigated. 50 nm thick IGZO films were deposited by radio frequency (RF) magnetron sputtering at room temperature and subsequently laser annealed in ambient conditions to enhance the IGZO electrical properties. Excimer laser annealing (ELA) was conducted by Krypton fluoride (KrF) excimer laser (λ= 248 nm) with single pulse over a range of fluences up to 175 mJ/cm2. The electrical properties of IGZO films were studied by four point probe (4PP) and Hall Effect measurements. Results demonstrated that the applied deposition conditions control the IGZO films metallic composition, which is found to be directly linked to IGZO films electrical properties. The as-deposited IGZO films were highly resistive with sheet resistance > 5 MΩ/sq and therefore 4PP and Hall Effect measurements could not be performed on the as-deposited films. Upon ELA, however, the sheet resistance is noticeably reduced to about 500 ± 10 % Ω/sq. Also, IGZO films demonstrated Hall mobility of 14 cm2/Vs and electron density of 3×1019/cm3 subsequent to ELA at 100 mJ/cm2. The reported findings present ELA as an efficient technique to engineer the electrical properties of sputter-deposited IGZO films. Therefore, a combination of room temperature deposition, via RF magnetron sputtering, and laser annealing could be used as a fabrication route of IGZO films for active layers of transparent thin film transistors (TTFTs) and applicable to flexible electronics which require low substrate temperature.