0.15-μm pattern formation using cell projection electron beam direct writing with variable shot size

An improved proximity effect correction method including Coulomb interaction effect correction for Gbit DRAMs is presented. When cell projection (CP) electron beam (EB) direct writing is applied to both the cell array region and peripheral region of DRAMs, cell projection shot (CPS) size must be optimized to prevent both the proximity effect and Coulomb interaction effect. Moreover, based on the results of Monte Carlo simulation, it has been shown that optimum doses of each shot must be calculated taking into account the beam blur. These optimum doses are dependent on line width and different even among patterns which have the same pattern density. We obtained 0.15-μm lines and spaces (L/S) patterns using a cell projection EB direct writing with the improved correction method.