The honeycomb-shape capacitor structure for ULSI DRAM

A way to increase the charge stored in polysilicon capacitors using surface modulation technology is proposed. Asperities on the polysilicon surface are achieved by reactive ion etching (RIE) of the polysilicon, using the oxide at the grain boundary as a mask. The fabricated polysilicon electrode has a honeycomb shape. With this structure, the capacitance is increased by four times for a polysilicon storage electrode of 250-nm thickness. The leakage current is comparable to that of convection stacked capacitors (STCs).>