High-field Breakdown and Thermal Characterization of Indium Tin Oxide Transistors

Abstract

Amorphous oxide semiconductors are gaining interest for logic and memory transistors compatible with low-temperature fabrication. However, their low thermal conductivity and heterogeneous interfaces suggest that their performance may be severely limited by self-heating, especially at higher power and device densities. Here, we investigate the high-field breakdown of ultrathin (~4 nm) amorphous indium tin oxide (ITO) transistors with scanning thermal microscopy (SThM) and multiphysics simulations. The ITO devices break irreversibly at channel temperatures of ~180 °C and ~340 °C on SiO${}_2$ and HfO${}_2$ substrates, respectively, with failure primarily caused by thermally-induced compressive strain near the device contacts. Combining SThM measurements with simulations allows us to estimate a thermal boundary conductance (TBC) of 35 $\pm$ 12 MWm${}^{-}$${}^2$K${}^{-}$${}^1$ for ITO on SiO${}_2$, and 51 $\pm$ 14 MWm${}^{-}$${}^2$K${}^{-}$${}^1$ for ITO on HfO${}_2$. The latter also enables significantly higher breakdown power due to better heat dissipation and closer thermal expansion matching. These findings provide insights into the thermo-mechanical limitations of indium-based amorphous oxide transistors, which are important for more reliable and high-performance logic and memory applications.