Stress Analysis of Silicon Carbide Microelectromechanical Systems Using Raman Spectroscopy

During the fabrication of Micro-Electro-Mechanical Systems (MEMS), residual stress is often induced in the thin films that are deposited to create these systems. These stresses can cause the device to fail due to buckling, curling, or fracture. Government and industry are looking for ways to characterize the stress during the deposition of thin films in order to reduce or eliminate device failure. Micro-Raman spectroscopy has been successfully used to analyze poly-silicon MEMS devices made with the Multi-User MEMS Process (MUMPS). Micro-Raman spectroscopy was selected because it is nondestructive, fast and has the potential for in situ stress monitoring. This research attempts to validate the use of Raman spectroscopy to analyze the stress in MEMS made of silicon carbide (SiC) using the Multi-User Silicon Carbide surface micromachining (MUSiC) process. Surface interferometry of fixed-fixed beam arrays and comb drive resonance test are employed to determine stress and compare it to the Raman values. Research also includes baseline spectra of 6H, 4H, and 15R poly-types of bulk SiC. Raman spectra of 1- to 2-m thick 3C-SiC thin films deposited on silicon, silicon nitride, and silicon oxide substrates are presented as an attempt to establish a baseline spectra for 3C-SiC, the poly-type of SiC found in MEMS made with the MUSiC process.