Impact of Annealing on Contact Formation and Stability of IGZO TFTs

Abstract

Annealing processes were investigated on Indium-Gallium-ZincOxide (IGZO) thin-film transistors (TFTs). Molybdenum and aluminum were used as contact metals which defined the working source/drain electrodes. Annealing was performed either pre-metal or post-metal deposition, in various gas ambients including air, oxygen, nitrogen, forming gas (5% H2 in N2) and vacuum. Premetal annealing in air ambient resulted in similar I-V characteristics on Mo-contact and Al-contact devices. A postmetal anneal for Mo-contact devices resulted in higher on-state current and steeper subthreshold slope, whereas the Al-contact devices experienced severe degradation suggesting the formation of an AlOx interface layer. A post-metal anneal at 400 °C in N2 followed by an air ambient ramp-down yielded Mo-contact devices with SS ~ 200 mV/dec, channel mobility µsat ~ 8.5 cm 2 /V•s, and improved stability over other anneal conditions.

A Fully Integrated Ferroelectric Thin‐Film‐Transistor – Influence of Device Scaling on Threshold Voltage Compensation in Displays

“…[33][34][35][36] In addition, a thermal treatment at such comparatively low temperatures is fully compatible to flexible-and glass substrates and minimizes the risk for inter-diffusion processes of metallic species at the interfaces between the a-IGZO channel and the metallic source and drain contacts, which are known to result in deteriorated TFT performance. [33,[37][38][39] Consequently, the maximum temperature to functionalize the HZO film is limited to 350 °C in the present processing scheme. Therefore, tailoring the HZO film to meet the thermal budget limitations defined by a-IGZO is highly desirable.…”

Self-aligned double injection-function contact mitigating short channel effects in sub-micron channels of solution processed indium gallium zinc oxide

“…The choice of metals was made due to the following considerations: As a rule of thumb, we 24 and others [31][32][33] found that post-metal-deposition annealing is required to reduce oxygen vacancies in the IGZO film. Also, it was reported that post-deposition annealing results in Molybdenum (Mo) being ohmic contact 34 and in platinum (Pt) becoming a Schottky contact 35 . The Al2O3 was chosen as a source insulator as it was found to show the best performance in our e-beam deposition system.…”

“…in Molybdenum (Mo) being ohmic contact 34 and in platinum (Pt) becoming a Schottky contact 35 . The Al2O3 was chosen as a source insulator as it was found to show the best performance in our e-beam deposition system.…”

Interpretation of Defect States in Sputtered IGZO Devices Using I-V and C-V Analysis

“…The importance of details regarding the annealing conditions has been described previously (7). Devices that had back-channel alumina were annealed at 400 °C in air ambient (45% humidity, class 1000 clean room) for 30 min.…”