A study on the electrical characteristics of InGaZnO thin-film transistor with HfLaO gate dielectric annealed in different gases

• Published in: Microelectronics and reliability Vol. 54; no. 11; pp. 2396 - 2400
• Main Authors: Qian, L.X., Lai, P.T.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2014; Elsevier
• Subjects: Amorphous InGaZnO (a-IGZO); Annealing; Annealing gas; Applied sciences; Carrier mobility; Dielectrics; Electronics; Exact sciences and technology; Gates; HfLaO; High-k; Hysteresis; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Swing; Thin films; Thin-film transistor (TFT); Threshold voltage; Transistors; Annealing gas; Thin-film transistor (TFT); HfLaO; Amorphous InGaZnO (a-IGZO); High-k; Performance evaluation; Voltage threshold; Amorphous material; Oxygen; Annealing; Vacancy; Charge carrier mobility; Transistor gate; 1/f noise; Gate oxide; Capacitance; Thin film transistor; Electron density; Electrical characteristic
• ISSN: 0026-2714; 1872-941X
• DOI: 10.1016/j.microrel.2014.04.011

•The effects of dielectric-annealing gas on a-IGZO TFT are studied.•The N2-annealed sample has a high saturation carrier mobility of 35.1cm2/Vs.•The O2-annealed sample shows poorer performance compared to the N2-annealed one.•The NH3-annealed sample displays the lowest threshold voltage (1.95V). The effects of dielectric-annealing gas (O2, N2 and NH3) on the electrical characteristics of amorphous InGaZnO thin-film transistor with HfLaO gate dielectric are studied in-depth, and improvements in device performance by the dielectric annealing are observed for each gas. Among the samples, the N2-annealed sample has a high saturation carrier mobility of 35.1cm2/Vs, the lowest subthreshold swing of 0.206V/dec and a negligible hysteresis. On the contrary, the O2-annealed sample shows poorer performance (e.g. saturation carrier mobility of 15.7cm2/Vs, larger threshold voltage, larger subthreshold swing of 0.231V/dec and larger hysteresis), which is due to the decrease of electron concentration in InGaZnO associated with the filling of oxygen vacancies by oxygen atoms. Furthermore, the NH3-annealed sample displays the lowest threshold voltage (1.95V), which is attributed to the increased gate-oxide capacitance and introduced positive oxide charges. This sample also reveals a change in the dominant trap type due to the over-reduction of acceptor-like border and interface traps, as demonstrated by a hysteresis phenomenon in the opposite direction. Lastly, the low-frequency noise of the samples has also been studied to support the analysis based on their electrical characteristics.