TW336346B - Double interface sealing local oxidation of silicon (LOCOS) - Google Patents

Abstract

A process for local oxidation of silicon, which at least comprises the following steps: forming a pad oxidation layer on a silicon substrate; forming a first silicon nitride layer on the pad oxidation layer; forming a photoresist layer on the first silicon nitride layer to define an active region; using the photoresist layer as the mask to remove a portion of the first silicon nitride layer and the pad oxidation layer; removing a portion of the edge of the pad oxidation layer to form a bottom-cut cavity underneath the first silicon nitride layer; forming a silicon dioxide layer on the silicon substrate on a region between the pad oxidation layer; forming a second silicon nitride layer on the silicon dioxide layer and on the first silicon nitride layer and filling the bottom-cut cavity; removing a portion of the second silicon nitride layer to form a silicon nitride gap wall on the side wall of the first silicon nitride layer, on the first silicon nitride layer and in the bottom-cut cavity; forming an amorphous silicon layer on the silicon nitride gap wall, on the first silicon nitride layer and the silicon dioxide layer; removing a portion of the amorphous silicon layer to form an amorphous silicon gap wall on the lower edge of the silicon nitride gap side wall and the silicon dioxide layer; forming a field oxidation region on the silicon substrate in the silicon nitride gap wall; removing the first silicon nitride layer; removing the silicon nitride gap wall; and removing the pad oxidation layer.