Suspended aluminum nitride structures grown via metal organic vapor phase epitaxy

Abstract

The development of III-Nitride suspended structures for Micro-Electro Mechanical Systems (MEMS) and Nano-Electro Mechanical Systems (NEMS) is challenging due to lack of selective etching techniques. Recent efforts have focused on the removal of sacrificial layers based on material properties, such as crystalline quality, bandgap, polarity, doping, etc. These techniques require several processing steps in addition to precise control over the sacrificial and functional layer properties. In this work, conditions have been identified for the growth of etch-resistant polycrystalline AlN films via Metal Organic Vapor Phase Epitaxy (MOVPE) on silicon oxide surfaces, thus allowing silicon oxide to be used as a sacrificial layer in a surface micro-machining process. The MOVPE growth conditions reported result in a well oriented crystal with superior mechanical strength demonstrated by the fabrication of unsupported AlN structures with widths from 5 μm to 110 μm and air gaps ranging from 200 nm to 800 nm. This technique simplifies the fabrication process of AlN suspended structures and is well suited for achieving group III-Nitride heteroepitaxial MEMS/NEMS systems.