After the NMOS threshold voltage (VT) adjust ion implantation and the subsequent photoresist ashing and cleaning, the thin implant screen oxide must be removed P4.This oxide was originally placed over the channel region to randomize the incoming ion trajectories, prevent channeling effects, and protect the bare silicon surface from metallic and organic contamination during the implant process T1.Because the high-energy ion bombardment physically damages the oxide network and embeds contaminants,