Method for enlarging surface area of a plurality of hemi-spherical grains on the surface of a semiconductor chip
 The present invention provides a method for enlarging the surface area of hemi-spherical grains on the surface of a semiconductor chip. The hemi-spherical grain structure is formed by combining a poly-silicon layer with an underlying amorphous silicon layer. In processing, the two layers are etched with a corrosive solution that etches the amorphous silicon layer at a higher rate than it etches the poly-silicon layer. In this way, a ring-shaped slot forms at the bottom of each hemi-spherical grain thus increasing the total surface area of the hemi-spherical grain structure. Furthermore, surface area of the storage node is increased and the cell capacitor capacitance increases in excess of 15%. 
Mosel Vitelic Inc.
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Yi-Fu Jui-Ping Ping-Wei Ming-Kuan
Chung Li Lin Kao