Metasurfaces are optical elements with nanoscale dimensions and planar profiles that expand the functionality and usefulness of traditional refractive optics. This has lead to considerable interest in metasurfaces for a variety of applications, including consumer electronics, automotive, and medical devices. Metasurface elements can be manufactured using standard microelectronics process techniques enabling mass production of optical elements in semiconductor foundries. Additionally, being produced at the wafer-scale, metasurfaces enable wafer-scale integration of optical systems. However, most metasurfaces to date have been produced in small-scale research settings using serial patterning techniques such as electron beam lithography. In order for metasurfaces to penetrate high volume applications, scalable production processes must be developed, including lithographic reproduction of metasurface design geometries. In particular, the constituent elements of metasurfaces, nanopillars, have shapes, aspect ratios, and local density variations which diverge from typical microelectronics design rules.
After a brief overview of metasurface fundamentals and their applications we will discuss traditional fabrication techniques, device requirements, and the challenges that arise when scaling to manufacturing. We will also discuss future generations of metasurfaces and further challenges in terms of geometry, critical dimensions, and materials compatibility.