Planar very high aspect ratio microstructures for large loading forces

We report on a novel technology called Scream for High Aspect Ratio Proportions (SHARP) which adds a new dimension to the Single Crystal Reactive Etching And Metallization (SCREAM) process. The fabrication technology increases the height and capacitive area of mechanical beams to improve the planarity and further extend the loading capabilities of very deep actuator structures. The process is based on a repeated sequence of thermal oxidations and reactive ion etches (RIE). Part of the technique consists of oxidizing through single crystal silicon (SCS) structural beams of a device by thermally growing a thick silicon dioxide (SiO2) layer (H-2/O-2 precursors) after the first trench RIE etch, thus yielding an ultra-thick (>30 mu m) SiO2 etch mask for further deep vertical etching (>100 mu m) to form high aspect ratio structures.