Impacts of Postdeposition Annealing on Interface Properties of HfO2/Si0.7Ge0.3 Gate Stacks With TMA Predoping

The impacts of postdeposition annealing (PDA) on the electrical characteristics and structural properties of HfO2/Si0.7Ge0.3 gate stacks using trimethylaluminum (TMA) predoping are investigated in detail. The interface state density ( ${D} _{\text {it}}$ ) first decreases and then increases under the PDA from $300~^{\circ }$ C to $600~^{\circ }$ C. Compared with PDA of $300~^{\circ }$ C, the minimum ${D} _{\text {it}}$ of $8\times 10^{{11}}$ eV $^{-{1}} \cdot $ cm $^{-{2}}$ is achieved at PDA of $400~^{\circ }$ C because the formation of Ge-O bonds at the interface is more effectively suppressed. As the PDA temperature further increases to $500~^{\circ }$ C and $600~^{\circ }$ C, the diffusion of Al into HfO2 causes the formation of an increasing number of Al-O bonds, and the oxygen defects within the Al-O network facilitates the diffusion of additional oxygen to the interface, resulting in the formation of more GeO that contribute to the deterioration of ${D} _{\text {it}}$ .