Experimental Study on NBTI Degradation Behaviors in Si pMOSFETs Under Compressive and Tensile Strains

In this letter, we experimentally investigated the effects of four types of strains, uniaxial tensile strain, uniaxial compressive strain, biaxial tensile strain, and biaxial compressive strain, on the negative bias temperature instability (NBTI) degradation behaviors of Si pMOSFETs. The strains were applied using a wafer bending system to avoid processing effects on the NBTI characteristics as a result of strain engineering. We confirm experimentally, for the first time, that both uniaxial and biaxial compressive strains are advantageous in terms of the NBTI improvement in Si pMOSFETs. However, the NBTI reliability was degraded under both uniaxial and biaxial tensile strains. These results could not be explained by considering only the gate leakage current change due to the strain. The strain-induced modulation of the interaction between the carriers and Si-H bonds at the interface must also be considered.