Method for achieving a highly reliable oxide film

Abstract

High quality oxides utilized in tunnel oxides and CMOS gate oxides are formed using a process that includes annealing a semiconductor substrate, after the oxide has been formed, in an ambient comprised of NO to form a surface layer in the oxide containing a concentration of nitrogen. A high-quality tunnel oxide, suitable for EEPROM devices, is formed upon a surface region of a semiconductor body over a heavily-doped N+ layer by first oxidizing the semiconductor body to form an oxide upon the surface region of the semiconductor body over the heavily-doped N+ layer. Next, the semiconductor body is annealed, under a gettering ambient, to densify the oxide and to dope the oxide at its surface and for a portion thereinto near its surface with a gettering agent. The semiconductor body is then oxidized, under an oxidizing ambient, to thicken the oxide. The annealing step in NO improves characteristics for both the gate and tunnel oxides of the device at a temperature substantially reduced from prior art methods and in an ambient atmosphere containing significantly more NO. The NO anneal can be performed in a variety of ways including an RTP anneal, a furnace anneal and can be performed on processes where the oxides are formed using CVD and PECVD.