Galvanic Corrosion of PN Junctions during the Dielectric Removal with HF for RMG Transistors

Abstract

For the high-k-last integration scheme both dummy poly-gate and dummy dielectric have to be removed before deposition of the novel metal gate. In this paper we will focus on the wet removal of the dummy dielectric by diluted HF selectively towards the silicon channel. Diluted HF is the chemical of choice due to its high selectivity towards silicon. In some cases however, the channel is attacked during this wet process step. Galvanic corrosion was identified as the detrimental mechanism for this attack. In this work a more detailed explanation of electrochemical corrosion behavior of doped silicon is given and compared with the observed results in devices. The silicon loss in the device samples is in good agreement with the experimentally obtained silicon loss measured for some non-device samples.