Process to form a trench-free buried contact

Abstract

A new method of forming an improved buried contact junction is described. A gate silicon oxide layer is provided over the surface of a semiconductor substrate. A polysilicon layer is deposited overlying the gate oxide layer. A hard mask layer is deposited overlying the polysilicon layer. The hard mask and polysilicon layers are etched away where they are not covered by a mask to form a polysilicon gate electrode and interconnection lines having a silicon nitride layer thereover wherein gaps are left between the gate electrode and interconnection lines. A layer of dielectric material is deposited over the substrate to fill the gaps. The had mask layer is removed. Thereafter, the polysilicon layer is etched away where it is not covered by a buried contact mask to form an opening to the semiconductor substrate. Ions are implanted into the semiconductor substrate within the opening to form the buried contact. A tungsten layer is selectively deposited overlying the buried contact and the polysilicon gate electrode and interconnection lines to form polycide gate electrodes and interconnection lines. The dielectric material layer is anisotropically etched to leave spacers on the sidewalls of the polycide gate electrodes and interconnection lines to complete the formation of a buried contact junction in the fabrication of an integrated circuit.