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 Characterist

The effects of Zr composition on the crystallization behaviors and reliability characteristics of atomic-layer-deposited Hf_1-x Zr_xO_y (0 ≤ x ≤ 1) gate-dielectric films are examined. n-Channel metal-oxide-semiconductor field-effect transistor (nMOSFET) devices with ZrO₂ gate dielectrics showed a much smaller V_th shift under the positive bias stress compared with the same device with HfO₂ gate dielectrics. The impact of Zr composition on the crystallization temperature, crystalline phases, and surface morphology of Hf_1-x Zr_xO_y films is studied. As the Zr composition in the Hf_1-x Zr_xO_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 ZrO₂ film is much smaller than that of crystallized HfO₂. The Hatband voltage (V_fb) shift under positive gate-bias stress in p-channel MOS capacitor (pMOSCAP) devices show a similar trend to the Vth shift in nMOSFET devices. In addition, the annealed ZrO₂ films show a large reduction in the V_fb, shift under the positive bias stress compared with as-deposited ZrO₂ in pMOSCAP devices. The improved bias-temperature-instability characteristics of ZrO₂ compared with that of HfO₂ is related to the smaller grain size of crystallized ZrO₂.