Low thermal budget PBTI and NBTI reliability solutions for multi-V-th CMOS RMG stacks based on atomic oxygen and hydrogen treatments

Abstract

We demonstrate a low temperature (T <= 280 degrees C) atomic oxygen (O*) treatment to suppress the electron trap density in HfO2 and improve PBTI in RMG stacks, matching the reliability of a standard high thermal budget flow. This novel high- k treatment is combined with our previously demonstrated low-T atomic hydrogen (H*) treatment of the chemOx IL for NBTI improvement, thus providing a complete BTI solution compatible with Sequential 3D integration and tightly spaced nanosheet stacks (e.g., CFET). For multi-V-th offerings, we deploy the low-T treatments with different Work Function Metal ( WFM) stacks and observe a systematic correlation between effective WF (eWF) and reliability, with low eWF beneficial for PBTI and detrimental for NBTI. Through Comphy simulations we show that these distinct correlations, together with the gate leakage increase at low eWF, are readily explained by assuming positive charge formation at the channel interface as the mechanism for eWF lowering in TiN/TiAl stacks with scaled TiN bottom layer. Finally, we discuss the EOT scalability of the low-T gate stacks with H* and O* treatments.