Lurie Nanofabrication Facility takes lead on Nanoscale Patterning on Nonplanar Surfaces using Electron Beam Lithography
Vishva Ray and Khaled Mnaymneh, University of Michigan
Patterning nanoscale geometries on curved and nonplanar surfaces is essential for next-generation devices particularly in the areas of flexible electronics, optics, metamaterials, bioengineering and fluidics. While current methods are extremely limited in applicability and scope, patterning nonplanar surfaces using electron beam lithography offers a distinct advantage with respect to feature sizes, repeatability and large surface area development. Recently, research engineers at the Lure Nanofabrication Facility successfully demonstrated high resolution patterning on curved and non-planar surfaces using their on-site JEOL JBX-6300FS electron beam lithography system.
Detailed in a recent paper1, the technique involves the continuous and automatic readjustment of the electron beam’s focal plane guided by a topological contour map of the substrate. The map data is acquired before the electron beam patterning by a noncontact high precision laser probe microscope. The paper then covers a few patterning examples that help to resolve important issues in current electron beam lithography while demonstrating capabilities worthwhile for new research avenues. For example, the variability of wafer tilt in conventional electron beam lithographic systems affects pattern repeatability across wafer. By automatically correcting for wafer height variations in situ, sample repeatability across the wafer would lead to better device reliability. The figure shows the results of focal plane compensation for a 50 nm line 100 nm pitch gratings on a wafer, shown in (a) with a 10 mm height variation. Grating patterns (b) through (f) show results across the height gradient yielding a 17% variation in linewidth similar to variations observed for gratings patterned on flat substrates.
In addition to correcting current write issues, writing nanostructures on curved lens or flexible media may facilitate interesting advances in sub-micron photonics2 or metamaterials for invisibility applications3. For questions about the technology or inquiries about using this exciting technology for your own research, please contact Vishva Ray (firstname.lastname@example.org) or Khaled Mnaymneh (email@example.com).
1 V. Ray et al., J. Vac. Sci. Technol. B. 30(6), (2012)
2 W. M. Choi et al., Nanotechnology 15, 1767, (2004)
3. G. X. Li, et al., Opt. Express, 20, 397 (2012)