Electron optical column for a multicolumn, multibeam direct-write electron beam lithography system

Electron beam direct-write lithography systems are capable of meeting the resolution requirements of all future ITRS nodes and have a significant cost of ownership advantage over masked technologies, but these systems typically have very poor throughput due to space charge limitations. Ion Diagnostics has developed a multicolumn, multibeam $(\mathrm{M\times M}\mathrm{™)}$ direct-write system that circumvents the space charge limitations by spreading the electron current over the wafer. The resulting lithography system can achieve critical dimensions of less than 100 nm with production throughputs greater than 60 wafers per hour, independent of wafer size. In this article we describe the electron optical column used in this system. We have developed a novel, microfabricated electron gun that produces 32 parallel electron beams that are individually controlled and blanked and contain deflectors that allow the gun optics to act as a perfect lens. Each column is $\text{2\hspace{0.05em}}\mathrm{cm}\text{×2\hspace{0.05em}}\mathrm{cm}$ and can align and scan the 32 beams in parallel on the wafer. The wafer voltage is typically held at 50–100 kV, and backscattered electrons are collected for imaging and alignment information. Theoretical results and some performance results for a prototype column are presented.