Multilayer etch masks for 3-dimensional fabrication of robust silicon carbide microstructures

This paper details the creation of 3-dimensional (3-D) microstructures in 4H-silicon carbide (4H-SiC) substrates with a plasma etch process that utilizes multilayer etch masks. An inductively coupled plasma (ICP) etch process (SF₆/O₂) for SiC was developed and etch rates as high as ~1 μm/min, a selectivity of 60:1 (SiC to Ni), and aspect ratio dependent etch characteristics were demonstrated. In addition, the selectivity of atomic layer deposited (ALD) Al₂O₃ etch masks to 4H-SiC is reported for the first time. Using this unique process, the microfabrication of complex microstructures (mechanical gears, Lego®-like bricks, and poker chips) is presented. The use of 4H-SiC as the structural material enables such microstructures to be utilized under high cycles of wear, within elevated temperatures, and within chemically corrosive environments.