Enhanced Reliability of High-Quality a-IGZO TFTs for Micro-LED Backplanes: Mitigating VTH Instability at Elevated Temperatures

This study examined the reliability of state-of-the-art a-IGZO thin-film transistors (TFTs) for next-generation micro-LED (μ-LED) display applications under high drain current stress at 120 °C. Although the control a-IGZO TFTs annealed at 300 °C exhibited excellent stability under the traditional PBTS conditions at 60 °C, the PBTS test at the elevated temperature of 120 °C resulted in a significant positive V_TH shift (ΔV_TH). In contrast, the high-quality (HQ) a-IGZO TFTs annealed at 400 °C exhibited markedly improved electrical stability, even in the PBTS test at 120 °C. A continuous density-of-states (DOS) extraction technique was proposed, enabling real-time tracking of defect evolution during reliability testing. Depth profiling (TOF-SIMS) confirmed that the HQ a-IGZO TFTs had a higher oxygen concentration and lower hydrogen content in the IGZO channel layer. This optimized stoichiometry mitigates defect formation, particularly hydrogen-related Frenkel defects (H_O⁺ to H-DX^- conversion), which were identified as the plausible origin of V_TH instability in the control TFTs under PBTS conditions at 120 °C. The HQ a-IGZO TFTs maintained exceptional reliability under such harsh operating conditions, showcasing their potential for μ-LED backplanes in demanding applications such as AR/VR/MR systems, automotive displays, and outdoor signage. These findings underscore HQ a-IGZO TFTs as a viable solution for the stringent performance and reliability requirements of next-generation display technologies.