Width-independent narrow nMOSFET reliability by split-well drive-in

Abstract

By splitting the well drive-in into two parts, before and after the field oxidation, it is possible to compensate the segregation effects due to field oxidation without having to increase the well concentration in the active areas. Due to the smaller dopant gradient between isolation and active areas, nearly neutral transistor-width dependence is achieved, resulting in width-independent transistor degradation behavior. Only in the case of threshold-voltage-adjustment directly by the p-well concentration is a weak reverse narrow-width effect observed. The reliability results show that the width effect on lifetime is turned eliminated. The lifetime reduction with decreasing transistor width, normally so critical for field-implanted devices, is not a problem. >