Method for manufacturing a capacitor using non-conformal dielectric

Abstract

A method of forming a capacitor on a semiconductor substrate includes forming a first oxide layer on the semiconductor substrate. A contact hole is then formed in the first oxide layer. A first conductive layer is formed on the first oxide layer and in the contact hole. Then the first conductive layer is etched to form a node structure. A non-conformal oxide is formed on the node structure so that the non-conformal oxide has an overhang portion and a lower portion on the sidewall of the node structure. The non-conformal oxide is isotropically etched to remove the lower portion of the non-conformal oxide and to expose the lower sidewall of the node structure. A second conductive layer is conformally deposited on the non-conformal oxide layer and the lower sidewall of the node structure. The second conductive layer is anisotropically etched, using the overhang portion of the non-conformal oxide as a mask. Then the non-conformal oxide is removed by using a highly selective etching process. The resulting conductive structure serves as a bottom storage node of the capacitor. A dielectric film is formed on the first conductive layer and the second conductive layer. A third conductive layer is formed over the dielectric film to form the top storage node of the capacitor.