Dielectric quality and reliability of FUSI/HfSiON devices with process induced strain

It is commonly believed that the process induced strain, used for device performance improvement, leads to worsen Negative Bias Temperature Instability (NBTI), due to weakening of the Si bonds at the substrate/dielectric interface. The introduction of strain involves additional processing steps, which may alter other electrical properties of the devices. These changes need to be taken into account in order to assure correct interpretation of the results. In this study we investigate the effect of compressive uni-axial strain on the device reliability and dielectric quality, using a gate stack, which has the least undesired changes in the electrical properties of the devices. The conclusion of our study is that no additional electrically active defects are created by the strain neither at the dielectric interface, nor in the bulk. Thus, reference devices and devices with process induced strain exhibit similar degradation mechanisms and similar low-frequency noise levels.