Characterization of Thermal Stability and Unexpected Mobility Enhancement in IGZO FETs Measured up to 750°C.

Abstract

In this work, we report the in-situ high-temperature electrical characteristics of atomic-layerdeposited (ALD) InGaZnO (IGZO) field-effect transistors (FETs). Transfer characteristics of IGZO FETs are measured up to 750 ◦C, where crystallization of the gate dielectric leads to degradation of transistor switching performance. Remarkably, the oxide channel material remains functional, and the FETs exhibit minimal degradation after 90 minutes at 600 ◦C, demonstrating the exceptional thermal stability of channel performance. An unexpected mobility enhancement is observed with increasing temperature. With the peak field-effect mobility (—FE) of 154 cm2V −1s −1 at 550 ◦C, this temperature-dependence contrasts with that of conventional single-crystal wide bandgap materials. The mobility enhancement is consistent with our nanocrystalline mobility model, which incorporates grain boundary (GB) scattering. At elevated temperatures, de-trapped defects transition into trapped states that no longer capture carriers, reducing the energy barrier (Eb) at the grain boundaries and enhancing mobility. Furthermore, the contact resistance (Rc) and sheet resistance (Rsh) are reduced by 81% and 72%, respectively, at 600 ◦C. This result underscores the strong potential of ALD oxide semiconductor FETs for Dynamic Random Access Memory (DRAM) and extreme-environment electronics.