Comparative study on NBTI kinetics in Si p-FinFETs with B2H6-based and SiH4-based atomic layer deposition tungsten (ALD W) filling metal

A comparative study on negative bias temperature instability (NBTI) is carried out in replacement metal gate Si p-FinFETs featuring atomic layer deposition (ALD) tungsten (W) filling metal using B2H6 and SiH4 precursors. A fast measurement technique is used to characterize the threshold voltage shift (Delta V-T). The effect of ALD W filling metal process on Delta V-T, generated interface traps (Delta N-IT), pre-existing hole traps (Delta N-HT), stress voltage, and temperature dependence of degradation is demonstrated. Comparing with their B2H6-based counterpart, SiH4-based devices show reduced Delta V-T under identical stress conditions due to reduced Delta N-HT and Delta N-IT. SiH4-based devices exhibit a 1.5 times higher fluorine content at the interfaces and larger compressive strain in the channel than B2H6-based devices, which are found to be responsible for the reduced Delta N-IT. A modeling framework is proposed to model the long-term time evolution of NBTI degradation, and the predicted maximum overdrive voltage is compared. SiH4-based devices exhibit superior reliability and a 20% improvement in the maximum operation overdrive voltage than B2H6-based devices, and can be implemented in the advanced CMOS technology.