Robust method of forming a cylinder capacitor for dram circuits

Abstract

A method of forming a capacitor for DRAM or other circuits is described which avoids the problem of weak spots or gaps forming between a polysilicon contact plug and the first capacitor plate. A layer of first dielectric is formed on a substrate, A layer of second dielectric is formed on the layer of first dielectric. A layer of third dielectric is formed on the layer of second dielectric. A first hole is formed in the first, second, and third dielectrics exposing a contact region of the substrate. The first hole is then filled with a protective material and a second hole is formed in the layer of third dielectric using the layer of second dielectric as an etch stop. The first hole lies within the periphery of the second hole. The protective material prevents re-deposition of the third dielectric. The remaining protective material is then removed and a layer of conducting material is formed on the top surface of the layer of third dielectric, the sidewalls of the second hole, the sidewalls of the first hole, and the contact region of the substrate thereby forming a first capacitor plate.