Thermally Stable Ruthenium Contact for Robust p-Type Tellurium Transistors

Abstract

Tellurium (Te) is attractive for p-channel transistors due to its high hole mobility. Despite having a low thermal budget suitable for back-end-of-line (BEOL) monolithic integration, the practical realization of Te transistors is hindered by its thermal stability. In this work, we investigate thermal stability for Te thin films grown via scalable thermal evaporation. Our findings identify ruthenium as a more thermally stable contact for p-type Te transistors, capable of withstanding temperatures up to 250 °C. Ruthenium exhibits significantly lower diffusivity in Te compared to other contact metals commonly used such as nickel and palladium. Using the transfer-length method, we measured a contact resistance of 1.25 kΩ·μm at the ruthenium–tellurium interface. Additionally, the incorporation of high-κ ZrO₂ encapsulation not only suppresses the sublimation of the Te channel at elevated temperatures but also serves as the gate dielectric in top-gate devices operating at 1 V, achieving an on/off current ratio of 10⁵.