Impacts of Zr Composition in Hf₁₋ₓ ZrₓOy Gate Dielectrics on Their Crystallization Behavior and Bias-Temperature-Instability Characteristics

The effects of Zr composition on the crystallization behaviors and reliability characteristics of atomic-layer-deposited Hf1-xZrxOy(0 ≤ x ≤ 1) gate-dielectric films are examined. n-Channel metal-oxide-semiconductor field-effect transistor (nMOSFET) devices with ZrO2gate dielectrics showed a much smaller Vthshift under the positive bias stress compared with the same device with HfO2gate dielectrics. The impact of Zr composition on the crystallization temperature, crystalline phases, and surface morphology of Hf1-xZrxOyfilms is studied. As the Zr composition in the Hf1-xZrxOyfilms increased, the reduction of crystallization temperature and the transformation from a monoclinic to a tetragonal phase were observed. The grain size of the crystallized ZrO2film is much smaller than that of crystallized HfO2. The Hatband voltage (Vfb) 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 ZrO2films show a large reduction in the Vfb, shift under the positive bias stress compared with as-deposited ZrO2in pMOSCAP devices. The improved bias-temperature-instability characteristics of ZrO2compared with that of HfO2is related to the smaller grain size of crystallized ZrO2.