Enhanced Reliability of High-Quality <i>a</i>-IGZO TFTs for Micro-LED Backplanes: Mitigating <i>V</i>_TH Instability at Elevated Temperatures

This study examined the reliability of state-of-the-art <i>a</i>-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 <i>a</i>-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 <i>V</i>_TH shift (Δ<i>V</i>_TH). In contrast, the high-quality (HQ) <i>a</i>-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 <i>a</i>-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 <i>V</i>_TH instability in the control TFTs under PBTS conditions at 120 °C. The HQ <i>a</i>-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 <i>a</i>-IGZO TFTs as a viable solution for the stringent performance and reliability requirements of next-generation display technologies.