METHOD OF FABRICATING DEEP TRENCH CAPACITOR

摘要

A method of fabricating a trench capacitor. A substrate is provided. A patterned mask layer to expose a portion of the substrate where a trench is to be formed. The exposed portion of the substrate is etched to form a trench. A conductive diffusion region is formed in the substrate surrounding a lower portion of the trench. A dielectric layer along an inner surface of the trench. The trench is filled with a first doped polysilicon layer. The first doped polysilicon layer and the dielectric layer are etched back to a first depth, so that a first recess is formed on the first doped polysilicon layer to expose an upper portion of the inner sidewall of the trench. A collar dielectric layer is formed on the exposed inner sidewall of the trench. The first recess is filled with a second doped polysilicon layer. The second doped polysilicon layer is etched back to a second depth, so that a second recess is formed on the second doped polysilicon layer to expose a part of the upper portion of the inner sidewall of the trench. The collar dielectric layer is etched until a surface level thereof is lower than a surface level of the second doped polysilicon layer, so that a gap is formed on the collar dielectric layer between the exposed inner sidewall of the trench and the second doped polysilicon layer. The gap is filled with a doped polysilicon layer converted from an undoped polysilicon layer. The patterned mask layer is removed, and a drain region adjacent to the doped polysilicon layer is formed.