Controlled nitrogen incorporation at the gate oxide surface

Nitrogen has been incorporated selectively at the top surface of a conventional thermal gate oxide by nitridation with a remote He–N2 plasma at low temperatures, 23 and 300 °C. On-line Auger electron spectroscopy (AES) has been used to characterize the process. A peak shift in the Si-LVV feature establishes that the nitrogen is bonded to the silicon. The concentration of nitrogen can be varied by a combination of substrate temperature and duration of plasma exposure. Ex situ glancing-angle x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) confirm that the nitrogen is confined to the immediate vicinity of the surface. Rapid thermal annealing (RTA) of the nitrided oxide at 900 °C in N2 and N2O does not change the N content.