EBES, a practical electron lithographic system

The continuing trend towards increasing complexity and decreasing feature size in integrated circuits is pushing photolithography to its limits. This is true for both mask generation and for the transfer of the mask pattern to the wafer. In mask making, step-and-repeat lenses are approaching their diffraction limits as feature sizes diminish and the overall pattern areas grow larger. In the case of pattern replication by optical projection or proximity printing, diffraction again limits the smallest feature which can be reproduced. Finally, in contact printing, both mask and wafer damage occur when the two are contacted, thus limiting the usefulness of this technique for large-area, fine-feature devices. If pattern exposure is carried out with electrons instead of light, these obstacles are removed. Electron beam pattern generation is becoming more efficient, and, in partnership with X-ray exposure techniques, it can offer a practical means for achieving the high resolution lithography demanded by complex integrated devices.