The Use of Metallographic and SEM Analysis for Characterization of Sidewall Surfaces in MEMS Devices with DRIE Processing

The Bosch Deep Reactive Ion Etch Process is commonly used for the manufacture of MEMS and MOEMS devices that require deep high aspect ratio trenches. In many cases fully released, high aspect ratio features can be generated in one pass. However the process must be understood to avoid generating some of the defect structures that are characteristic of the process. Defects such as scalloping, silicon grass, and undercutting at the interface of a nonconductive layer can be controlled by process parameters and optimization. Measurement and characterization of the defective structures is a key element of controlling them. The use of SEM measurement techniques for characterizing the small features associated with scalloping and silicon grass is essential. No other technique is capable of providing the large depth of focus required to visualize these features. The use of metallographic techniques furthers understanding of the surface conditions on the side walls of these deep trenches.