A method for controlling interfacial oxide at a polycrystalline/monocrystalline silicon interface

摘要

A method of controlling the quantity and uniformity of distribution of bonded oxygen atoms at the interface between the polysilicon and the monocrystalline silicon consists in carrying out, after having loaded the wafer inside the heated chamber of the reactorand evacuated the chamber of the LPCVD reactor under nitrogen atmosphere, a treatment of the wafer with hydrogen at a temperature generally comprised between 500 and 1200 DEG C and at a vacuum generally comprised between 0.1 Pa and 60000 Pa, and preferably at a temperature of 850 DEG C +/- 15 DEG C and at a vacuum of 11000 Pa +/- 2000 Pa, for a time generally comprised between 0.1 and 120 minutes, and most preferably between 0.5 and 1.5 minutes, in order to remove any and all the oxygen that may have combined with the silicon on the surface of the monocrystalline silicon during the loading inside the heated chamber of the reactor even if it is done under a nitrogen flux. After such a hydrogen treatment, another treatment is carried out substantially under the same vacuum conditions and at a temperature generally comprised between 700 and 1000 DEG C with nitrogen protoxide (N2O) for a time generally comprised between 0.1 and 120 minutes, preferably between 0.5 and 1.5 minutes. The treatment with nitrogen protoxide (N2O) at such a vacuum and temperature conditions causes a relatively slow oxidation of the monocrystalline silicon and allows an effective control of the amount of oxygen at the interface and a great uniformity of distribution of it on the surface. The tunnel barrier characteristics in respect to the holes of the so created oxide film at the interface between the monocrystalline silicon and the polysilicon layer show an outstanding reproducibility.