Method of forming hemispherical grains on a surface comprising pre-cleaning the surface in-situ with plasma

Abstract

A method of forming a hemispherical grain includes cleaning a polysilicon layer of a native oxide in-situ in the processing chamber of the HSG growth reactor. Such a native oxide adversely affects the growing of HSGs from seeds during the thermal treatment performed in the processing chamber. The cleaning is carried out by dry etching the polysilicon layer with plasma. The plasma may be produced from a mixture of fluorine and inert gases having a volumetric ratio within the range of 0.2:100 to 25:100. Such a plasma can be formed by ionizing the gas with an RF power within a range of 20 to 500 Watts. An advantage of using plasma etching to clean the polysilicon of a native oxide is that the plasma etching is an anisotropic process. The present invention is thus particularly useful in the manufacture of a DRAM capacitor. In such a case, the hemispherical grains at neighboring side walls of the DRAM capacitor have a smaller average grain size than that of the hemispherical grains at the upper surfaces of the capacitor. The smaller HSGs are less likely to bridge, and yet the capacitor may still have some comparatively large grains contributing to the increased capacitance provided by the HSGs.