Impacts of Zr Composition in $hbox{Hf}_{1-x} hbox{Zr}_{x}hbox{O}_{y}$ Gate Dielectrics on Their Crystallization Behavior and Bias-Temperature-Instability Characteristics

摘要

The effects of Zr composition on the crystallization behaviors and reliability characteristics of atomic-layer-deposited $hbox{Hf}_{1-x}hbox{Zr}_{x}hbox{O}_{y} (hbox{0} leq x leq hbox{1})$ gate-dielectric films are examined. n-Channel metal–oxide–semiconductor field-effect transistor (nMOSFET) devices with $hbox{ZrO}_{2}$ gate dielectrics showed a much smaller $V_{ rm th}$ shift under the positive bias stress compared with the same device with $hbox{HfO}_{2}$ gate dielectrics. The impact of Zr composition on the crystallization temperature, crystalline phases, and surface morphology of $hbox{Hf}_{1-x}hbox{Zr}_{x}hbox{O}_{y}$ films is studied. As the Zr composition in the $hbox{Hf}_{1-x}hbox{Zr}_{x}hbox{O}_{y}$ films increased, the reduction of crystallization temperature and the transformation from a monoclinic to a tetragonal phase were observed. The grain size of the crystallized $hbox{ZrO}_{2}$ film is much smaller than that of crystallized $hbox{HfO}_{2}$. The flatband voltage $(V_{rm fb})$ shift under positive gate-bias stress in p-channel MOS capacitor (pMOSCAP) devices show a similar trend to the $V_{rm th}$ shift in nMOSFET devices. In addition, the annealed $hbox{ZrO}_{2}$ films show a large reduction in -n-nthe $V_{rm fb}$ shift under the positive bias stress compared with as-deposited $hbox{ZrO}_{2}$ in pMOSCAP devices. The improved bias-temperature-instability characteristics of $hbox{ZrO}_{2}$ compared with that of $hbox{HfO}_{2}$ is related to the smaller grain size of crystallized $hbox{ZrO}_{2}$.