Pocl.sub.3 process flow for doping polysilicon without forming oxide

Abstract

In a method of introducing phosphorous from phosphorous oxychloride (POCl.sub.3) into an undoped gate polysilicon region formed as part of an integrated circuit structure, an initial MOS structure is developed utilizing conventional techniques through the formation of a layer of undoped polysilicon over thin gate oxide. A POCl.sub.3 layer is then formed over the undoped polysilicon and thermally annealed to drive phosphorous into the gate polysilicon to achieve a desired conductivity level. The phosphorous-rich organic layer is then cleaned from the surface of the POCl.sub.3 using sulfuric peroxide and the POCl.sub.3 layer is removed using a DI:HF solution to expose the surface of the doped polysilicon. After formation of a photoresist gate mask, arsenic, or another heavy ion species, is implanted into the exposed polysilicon to amorphized the exposed poly, thereby eliminating the polysilicon grain boundaries. This leads to uniform etching of the amorphized poly and, therefore, disappearance of the oxide pillars. Removal of the organic layer from the POCl.sub.3 Layer prior to the HF deglaze step facilitates smooth, uniform etching of the POCl.sub.3 in reduced time, thereby eliminating the gate oxide holes experienced in the conventional process flow.