Re-investigation of frequency dependence of PBTI/TDDB and its impact on fast switching logic circuits

In this paper, frequency dependence of the Positive Bias Temperature Instability (PBTI) and the Time Dependent Dielectric Breakdown (TDDB) at relative high frequency range (1KHz ~ 500MHz) in high-k/metal-gate (HK/MG) NMOS are investigated. An explanation of both dependencies of PBTI and TDDB with capture/emission times is proposed. This paper is divided into three parts: 1) AC PBTI and the existence of critical frequencies is discussed, 2) Frequency dependence of TDDB and its implication of the time to form leakage path, and 3) AC BTI/TDDB impacts on logic circuit, which is studied using simulated frequency degradation of ring oscillators (ROs). Based on the negligible frequency degradation of RO with worst Idsat degradations, we conclude that, for circuits operating in a continuous switching mode, BTI/TDDB will not be an unsurpassable reliability issue.