Methods of forming hsg capacitors from nonuniformly doped amorphous silicon layers and hsg capacitors formed thereby

Abstract

A hemispherical grain (HSG) capacitor having HSGs on at least a part of the surface of capacitor lower electrodes, and a method of forming the same. In the capacitor, lower electrodes are formed of at least two amorphous silicon layers including an amorphous silicon layer doped with a high concentration of impurities and an amorphous silicon layer doped with a low concentration of impurities, and HSGs are formed, wherein the size of the hemispherical grains can be adjusted such that the size of HSGs formed on the inner surface of a U-shaped lower electrode or on the top of a stacked lower electrode is larger than that of HSGs formed on the outer surface of the U-shaped lower electrode or on the sidews of the stacked lower electrode. Thus, bridging between neighboring lower electrodes can be avoided by appropriately adjusting the size of HSGs, resulting in uniform capacitance wafer-to-wafer and within a wafer. The mechanical strength of the U-shaped lower electrode can also be enhanced.