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

The effects of Zr composition on the crystallization behaviors and reliability characteristics of atomic-layer-deposited Hf
_1-x
Zr
_x
O
_y
(0 ≤ x ≤ 1) gate-dielectric films are examined. n-Channel metal-oxide-semiconductor field-effect transistor (nMOSFET) devices with ZrO
₂
gate dielectrics showed a much smaller V
_th
shift under the positive bias stress compared with the same device with HfO
₂
gate dielectrics. The impact of Zr composition on the crystallization temperature, crystalline phases, and surface morphology of Hf
_1-x
Zr
_x
O
_y
films is studied. As the Zr composition in the Hf
_1-x
Zr
_x
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 ZrO
₂
film is much smaller than that of crystallized HfO
₂
. 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 ZrO
₂
films show a large reduction in the V
_fb
, shift under the positive bias stress compared with as-deposited ZrO
₂
in pMOSCAP devices. The improved bias-temperature-instability characteristics of ZrO
₂
compared with that of HfO
₂
is related to the smaller grain size of crystallized ZrO
₂
.