Further advances in electron-beam pattern generation technology for 180-nm masks

The technology in use in today's mask shop may not be adequate to meet 180 nm production requirements. In particular, requirements for linewidth control, linewidth uniformity, and registration are tightening at a breakneck pace. In the past, incremental improvements to registration and linewidth have been adequate to keep pace with steadily evolving mask requirements. This paradigm of continuous incremental improvement is not longer a valid model. Mask writers are needed that can deliver a higher dose to support advanced resists for superior critical dimension (CD) control, write faster to compensate for shrinking device sizes, and incorporate advanced calibration and error control schemes to improve placement accuracy. This paper describes key electron-beam pattern generation activities necessary to meet 180 nm mask requirements. This includes testing and implementation of multipass graybeam to improve throughput at lower addresses without compromising lithography quality, a new resist and process capable of supporting dry etching, and a data path capable of supporting addressing to 10 nm. Multipass gray (MPG) writing strategy was introduced with the MEBES 4500S. The ability to deliver a 4X improvement in dose while improving throughput is a significant advantage over previous MEBES systems. Because MPG is used in conjunction with offset scan voting, improvements in registration performance and a reduction in butting of over 50 percent have been demonstrated. Some of the process improvements attributed to a high dose mask writer are also documented in this paper. CD uniformity improvements with ZEP 7000 and dry etch at a 720 nm nominal feature size and smaller are also discussed in some detail.