Fabrication of 3D Metamaterial Resonators Using Self-Aligned Membrane Projection Lithography
✍ Scribed by D. Bruce Burckel; Joel R. Wendt; Gregory A. Ten Eyck; A. Robert Ellis; Igal Brener; Michael B. Sinclair
- Book ID
- 102690232
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 544 KB
- Volume
- 22
- Category
- Article
- ISSN
- 0935-9648
No coin nor oath required. For personal study only.
✦ Synopsis
Fabrication of 3D Metamaterial Resonators Using Self-Aligned Membrane Projection Lithography
Artifi cially structured materials are becoming increasingly important in fi elds such as metamaterials, [ 1 ] plasmonics, and optics. Fabrication of composite materials with designed constituent elements of sub-micrometer size typically requires cutting edge lithography techniques such as immersion lithography, nanoimprint lithography, or e-beam lithography. While these techniques are capable of printing features with the requisite lateral dimensions, they are all planar patterning approaches, and hence offer limited options for creation of 3D structures, or structures with out-of-plane components. Other patterning techniques such as interferometric lithography are capable of creating 3D structures, but are typically limited to periodic patterns, while direct write approaches are serial, [ 8 ] and hence do not scale well, severely limiting the design space.
We introduce a fabrication technique called membrane projection lithography (MPL) which combines planar lithography with a sequence of processing steps to create micrometer-scale structures with out-of-plane components. The method is general, and can be repeated in a layer-by-layer fashion to create 3D volumetric materials with engineered inclusions. The basic premise behind MPL is to create a patterned membrane positioned over a cavity, and then use directional evaporation through the membrane to deposit instances of the membrane pattern on the interior face of the cavity. We fabricate micrometerscale metallic resonators using two separate MPL process fl ows: self-aligned MPL (SAMPL), and single-evaporation MPL (SEMPL). MPL is somewhat related to microstencil fabrication used in micro electromechanical systems (MEMS) fabrication, although the size scale, and linewidths of the patterns we present here are typically at least a factor of 10 smaller than those reported elsewhere. [ 9 ] Consider the self-aligned membrane projection lithography (SAMPL) process fl ow depicted in Figure . This variant of MPL begins by deposition of a membrane material on a substrate (Figure ). Standard planar lithography (either optical lithography or e-beam lithography) is used to pattern the membrane (Figure ). The holes in the patterned membrane are then used as access ports to allow for local dissolution and removal of the substrate, forming cavities underneath each hole (Figure ). Depending on the isotropy of the substrate dissolution etch