Improved reliability of HfO2/SiON gate stack by fluorine incorporation

Effects of fluorine (F) incorporation on the reliabilities of pMOSFETs with HfO₂/SiON gate stacks have been studied. In this letter, fluorine was incorporated during the source/drain implant step and was diffused into the gate stacks during subsequent dopant activation. The authors found that F introduction only negligibly affects the fundamental electrical properties of the transistors, such as threshold voltage V_th, subthreshold swing, gate leakage current, and equivalent oxide thickness. In contrast, reduced generation rates in interface states and charge trapping under constant voltage stress and bias temperature stress were observed for the fluorine-incorporated split. Moreover, the authors demonstrated for the first time that F incorporation could strengthen the immunity against plasma charging damage.