The Impact of an Ultrathin Y2O3 Layer on GeO2 Passivation in Ge MOS Gate Stacks

This paper investigates the impact of an atomic layer-deposited Y
₂
O
₃
dielectric on the passivation of a GeO
₂
layer in GeO
₂
-based Ge gate stacks. The equivalent oxide thickness scalability and thermal stability of the ultrathin Y
₂
O
₃
layer are evaluated at different Y
₂
O
₃
thicknesses and annealing conditions in detail. Experimental results show that a Y
₂
O
₃
layer thickness of 1.0 nm is required to serve as a GeO
₂
passivation layer while retaining gate-stack performance at 400 °C postdeposition annealing. However, at a higher annealing temperature of 500 °C, the barrier property deteriorates and allows GeO desorption. The proposed gate-stack implies the applicability of a Y
₂
O
₃
passivation method for further scaled GeO
₂
-based Ge gate stacks.