Fabrication of Microstructures by Wet Etching of Anodic Aluminum Oxide Substrates

Abstract

Anodic aluminum oxide (AAO) was used as substrates of microstructure fabrication. Complex structures with high aspect ratios were obtained by the single-step wet etching of the AAO substrates. Structures with different shapes and aspect ratios could be simultaneously obtained with vertical sidewalls. The surface morphology of the fabricated structures could be tailored. It is expected that various MEMS/NEMS devices can be built using this technique.

Microcantilevers with Nanochannels

“…The presence of nanochannels in the AAO made the anisotropic etching of the complex patterns possible. [27] Note that the photoresist layer and the transfer layer still exist on top of the AAO structures. Suspended cantilevers are fabricated by removing the aluminum under the patterns without damaging the AAO.…”

Microcantilevers with nanowells as moisture sensors

“…The transfer layer provides the surface with high reflectivity and helps to obtain sharp patterns after lithography [20]. A thin layer of PR (AZ1512) was spincoated onto the substrate at 4000 rpm for 45 s and microstructures were patterned by carrying out UV exposure for 20 s. The exposed pattern (reacted PR) was removed by rinsing in AZ developer (CD30) for 1 min.…”

Electrochemically Fabricated Microelectromechanical Systems/Nanoelectromechanical Systems (MEMS/NEMS)

“…The versatility of these anodized aluminum templates extends to three-dimensional structures, including cylinders and multifaceted objects [62]. Alumina templates can also be easily integrated into existing CMOS technologies, by utilizing a wet etching technique for creating complex shapes with vertical side walls [63] Lateral anodic oxidation of Al thin films has also been established on SiO 2 substrates. [64].…”