Abstract
A simplified method of effective work function (Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> ) control to near the Si conduction band edge ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ec</i> ) was demonstrated in the Ni fully silicided (Ni-FUSI) gate/HfSiON system. The Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> of NiSi (4.51 eV) decreased and saturated at 4.27 eV, owing to the use of an Al postdoping process, in which the implantation of Al ions into the upper part of the Ni silicide gate electrodes was followed by low-temperature drive-in annealing ( les 500degC) . There is no degradation of the gate leakage characteristics at the Ni-FUSI/HfSiON interface. The metallic state of piled-up Al just at the Ni-FUSI/HfSiON interface seems to be responsible for the Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> near the vacuum work function of Al. The Al postdoping process simplifies a dual metal gate process, owing to single-step Al implantation for nMOS devices without complicated metal etching process for pMOS region. The physical mechanism of bidirectional Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> modulation of Al pileup was also investigated. It was revealed that the opposite Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> modulation, which is the increase in Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> , occurs, owing to the formation of interfacial Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> layer at the Ni-FUSI/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface. Although the Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> state also formed, it has little influence on the Phi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> value at the Ni-FUSI/HfSiON interface.
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