As semiconductor features shrink in size and pitch, there are strong needs for an advanced mask writer which has better patterning quality. Among various requirements for next photomask writer, we have focused on the requirements of ebeam size and position accuracy for hp 32nm and beyond generation.At the era of DPT, EUV, and complex OPC, the photomask is required to have extreme control of critical dimension (CD). Based on simulation and experiment, we present the e-beam requirements for advanced mask writer, in view point of stability and accuracy. In detail, the control of e-beam size in mask writer should be decreased to 0.5nm because the size error of e-beam gives rise to large CD error according to the high complexity of mask pattern. Furthermore, the drift error of beam position should be smaller than 1nm to obtain the tight pattern placement error and to minimize the edge roughness of mask pattern for the era of computational lithography and EUV lithography.