The study of compressive and tensile stress on MOSFET´s I-V, C-V characteristics and it´s impacts on hot carrier injection and negative bias temperature instability

The effects of compressive and tensile stresses from the etch stop layer on DC and AC characteristics and device reliabilities (HCI and NBTI) of IO n-/p-MOSFETs have been studied. Although tensile stress can increase the Idsat (∼8%) of nMOSFETs, the higher process temperature of thermal SiN deposition also results in worse Vt roll-off for nMOSFETs and poly depletion effects on pMOSFETs. In this experiment, thermal SiN films with tensile stress result in HCI and NBTI lifetime degradation. HCI lifetime reduction is about 3× for nMOSFETs and 7× for pMOSFETs. Tensile stress also enhances the channel length dependence effect of pMOSFET NBTI lifetime. Compared with PECVD SiN, thermal SiN results in about a 5× lifetime reduction for short channel pMOSFETs.