Significant Threshold Voltage Shift Induced by Ge Penetration into PMOSFET Channel of 28-nm SRAM

摘要

A significant positive threshold voltage shift for the PMOSFET of a 28-nm SRAM is reported in this letter. For the first time, it is revealed that Ge atomsmay penetrate into the channel of a PMOSFET with embedded SiGe (eSiGe) source/drain (S/D). It is proposed that the localized high content of hydrogen radicals causes the penetration, and these radicals are related to GeH4 decomposition during eSiGe deposition. The penetration is eliminated by removing GeH4 from the SiGe cap layer deposition.