Mobility improvement after HCl post-deposition cleaning of high-κ dielectric: a potential issue in wet etching of dual metal gate Process technology

The effect of deionized water and dilute hydrochloric acid, 500:1 (HCl) post-Hf-silicate deposition cleaning on the device characteristics of Hf-silicate MOSFETs have been investigated. The results suggest that a significant improvement in mobility and equivalent oxide thickness scaling can be obtained using HCl post-treatment in comparison to control and H₂O post-treated devices. The enhancement in bulk trapping immunity has been attributed to the reduced charge trapping in the bulk high-κ layers, whereas no apparent change in interface properties could be observed. The effect of the post-deposition cleaning might have important implications on the wet etching of gate metals in dual-metal-gate technology.