Process for forming MNOS dual dielectric structure

Claim 1

A process for forming continuously in the same furnace deposition tube a silicon dioxide, silicon oxynitride and silicon nitride memory device dielectric structure on a silicon substrate comprising: thermally oxidizing the silicon substrate in the furnace tube in a dry oxygen ambient atmospheric pressure in the range of 700°-850° C.; forming immediately thereafter the silicon oxynitride layer on the silicon dioxide using gaseous reactants in the proportion (1-3):2:7 of N 2 O, dichlorosilane and ammonia, said ammonia being introduced first into the furnace tube to prevent spurious deposits during this step, at the same temperature used for forming the silicon dioxide layer and a pressure of 400-600 millitorr; and forming immediately thereafter the silicon nitride layer on the silicon oxynitride by cutting off the N 2 O gas supply to the furnace tube and using the gaseous ammonia and dichlorosilane in the ratio of (3-4):1 at the same temperature and same range of pressure used for forming the silicon oxynitride layer.