Journal of the Electrochemical Society, Vol.141, No.9, 2498-2502, 1994
Eliminating the Surface Inversion Layer Under the Field Oxide by Low-Pressure Rapid Thermal Annealing
A rapid thermal anneal (RTA) at low pressure is proposed as an efficient method for the elimination of the surface inversion layer formed by the charges within the field oxide or by the leakage current along the field oxide surface which is easily contaminated by photoresist, water molecules, and mobile ions. From the high-low frequency C-V measurements, it was found that a 900-degrees-C RTA at a pressure of 300 Torr can remove the field oxide surface contaminants sufficiently and make the distorted portion in the strong inversion region of the high frequency C-V curve return to normal. The practice of rapid thermal annealing after chemical etching and cleaning can prevent the field oxide surface from contamination caused by the subsequent high temperature process. It was also found that after a low pressure RTA the gate oxide endurance can be dramatically enhanced and is comparable to that of the conventional furnace-annealed gate oxide.