Method of fabricating an extended self-aligned crown-shaped rugged capacitor for high density dram cells

Abstract

The method of the present invention for forming a capacitor on a semiconductor substrate includes the following steps. At first, a first oxide layer is formed over the substrate and a nitride layer is then formed over the oxide layer. A second oxide layer is then formed over the nitride layer and a first silicon layer is formed over the second oxide layer. Next, a node opening is defined in the first silicon layer, the second oxide layer, and the nitride layer, upon the first oxide layer. Sidewall structures are then formed on sidewalls of the node opening. A contact opening is then defined in the first oxide layer under the node opening. The contact opening is defined in the first oxide layer under a region uncovered by the sidewall structures. The sidewall structures and a portion of the nitride layer nearby the node opening are removed to form undercut structures under the second oxide layer. A second silicon layer is then formed conformably over the contact opening, the undercut structures, the node opening, and the first silicon layer. A node-top defining layer is formed on the second silicon layer and is patterned to leave a node-top defining region. Next, a portion of the second silicon layer and a portion of the first silicon layer uncovered by the node-top defining region are removed. Silicon sidewalls are formed on sidewalls of the node-top defining region, and are communicated to the first silicon layer and the second silicon layer to form an electrode. The node-top defining region, the second oxide layer, and the nitride layer are removed. A wet etch is performed to remove the nitride layer and to roughen the surface of the electrode. A dielectric film is then formed conformably over the electrode. Finally, a conductive layer is formed over the dielectric layer.