The primary task of this project is to design, fabricate, and characterize the comb-actuated nanomirror array for EUV maskless lithography to print feature sizes below 100 nm. The technological challenges facing the nanomirror fabrication come from the need to fabricate sub-micron mirrors with sub-50 nm vertical comb gaps, for which a self-aligned process is necessary to build a hidden-hinge and double-comb structure. Moreover, the analog “gray-scaling” printing scheme requires a clear understanding of the difference between the posicast switching and biased switching in an analog scheme. A continuing research effort on this dynamic will follow in the future.
A preliminary process has been designed and tested successfully. Vertical sub-micron comb structures (without a hinge) with released 50 nm comb gaps have been achieved (see figure). We have identified some problems of the process and are currently optimizing the fabrication parameters for further improvement of device structure. We are also investigating the relevant process to form a mirror-compatible amorphous Si thin film with satisfactory photosensitive and resistive properties (for electrical damping).
Figure 1: The SEM pictures of fabricated nanocomb structures with 50-nm comb gaps