Polysilicon gate reoxidation in a gas mixture of oxygen and nitrogen trifluoride gas by rapid thermal processing to improve hot carrier immunity

摘要

A method of forming an FET transistor comprises forming a stack of a gate oxide layer and a control gate electrode on a surface of a doped semiconductor substrate with counterdoped source/drain regions therein. A silicon oxide layer is formed over the stack of the gate oxide layer and the control gate electrode and exposed portions of the semiconductor substrate including the source/drain regions. Then the silicon oxide layer and the corners of the gate oxide layer are fluorinated by rapid thermal processing providing a fluorinated silicon oxide layer. The rapid thermal processing is performed in an atmosphere of NF.sub.3 gas and O. sub.2 gas at a temperature from about 900° C. to about 1050° C. for a time duration from about 10 seconds to about 50 seconds, and the fluorinated silicon oxide layer has a thickness from about 200 Å to about 400 Å.