Cell projection using an electron beam

A method for aligning a beam passing through a cell aperture with a designed location in a cell projection process, comprising the steps of selecting from design data first and second pattern for cell projection of first and second shot areas, respectively, calculating a coordinate difference between coordinates of said first pattern and coordinates of said second pattern, passing a beam through a first cell aperture having said first pattern to obtain a first shot area, then passing a beam through a second cell aperture having said second pattern by using said coordinate difference to obtain a second shot area so that said second shot area is located at a design difference with respect to said first shot area, calculating an offset value based on a difference between said design difference and an actual difference measure between the two patterns exposed on a semiconductor wafer, conducting a plurality of cell projections using at least said first cell aperture and said second cell aperture on said semiconductor wafer based on said design data and said offset value.