Patent ID: 6326261
Filing Date: 2001-12-04
Classification: H01L

Abstract:
A method of fabricating a deep trench capacitor in a DRAM cell comprising:providing a substrate, over which a patterned pad stack is positioned;etching the substrate using the patterned pad stack as a mask to form a deep trench within the substrate;forming a buried plate within the substrate underneath the deep trench;forming a dielectric layer on the surfaces of both the substrate and the deep trench;positioning a photoresist layer in the deep trench, aligning the surface of the photoresist layer with the tops of the buried plate;removing the dielectric layer uncovered by the photoresist layer to expose the area of the substrate in the upper region of the deep trench;removing the photoresist layer;performing an oxidation process to form a first oxide film on the dielectric layer and to form a second thicker oxide film on the exposed substrate in the deep trench;forming a doped polysilicon layer to cover the surface of the substrate as well as completely filling in the deep trench;performing a first planarization process, using the pad stack as a stop layer, to align the surface of the doped polysilicon layer within the deep trench with that of the pad stack;performing a first polysilicon recess etching process to etch back the doped polysilicon layer and lower the surface of the doped polysilicon layer down to the substrate;removing a portion of the second thicker oxide film to expose the area of the substrate in the upper region of the deep trench;forming an undoped polysilicon layer to cover the surface of the substrate as well as completely filling in the deep trench;performing a second planarization process, using the pad stack as a stop layer, to align the surface of the undoped polysilicon layer within the trench with that of the pad stack;performing a second polysilicon recess etching process to etch back the undoped polysilicon layer and lower the surface of the undoped polysilicon layer down to the pad stack, to form a storage node; andremoving the pad stack.