A Comparison of 20 kV vs. 50 kV E-Beam Lithography for MOS Circuit Fabrication

The progressive scaling of device dimensions into the sub-micron range has increased the merit of e-beam direct-writing for IC fabrication. Not only do e-beams allow for the fabrication of VLSI chips with finer critical dimensions than hitherto feasible with conventional techniques, they also provide excellent resolution, and can thus serve to explore fundamental device physics. In addition, e-beam direct-writing is a cost-effective technique for low-volume prototyping of ASIC codes and can be used to an advantage for quick turn-around design verification. Most e-beam exposure systems developed for wafer-writing have been designed to operate at voltages no greater than 20-30 kV in order to obtain the desired machine accuracy and throughput, without increasing the complexity of the electron-optical column design.