Anomalous diffusion of dopant in Si substrate during oxynitride process

Unexpectedly enormously enhanced diffusions of B and P in Si substrate during gate oxynitride process have been clarified for the first time. The apparent diffusion enhancement is observed in the reoxidation process after nitridation in NH/sub 3/ ambient. The oxidation enhanced diffusion (OED) factors of B and P are about 15 times larger than the normal OED factor, which is ascribed to the increase of interstitial Si at oxynitride/Si interface. The enormously enhanced diffusion affects the device characteristics and should be taken into account in order to perform accurate simulation for submicron MOSFETs with oxynitride gate.