Abstract
A method of fabricating suspended LPCVD and PECVD silicon nitride structure is demonstrated for a wide range of MEMS (Micro-Electro-Mechanical Systems) applications. Low stress LPCVD and PECVD silicon nitride film of 1 μm thickness were selected for the structure separately. Optical Lithographic parameters, viz, photoresist (PR) thickness, PR variety and baking parameters were optimized to obtain the PR suitable for selective etching of silicon and silicon nitride. Parameters of the dry etching process were also optimized to achieve anisotropic etching of silicon nitride and isotropic etching of Si to release the silicon nitride beam. The silicon nitride structures, thus released, were characterized using Scanning Electron Microscope (SEM) and Laser Doppler Vibrometer (LDV). Finite Element Method (FEM) analysis was carried out using COMSOL, to compare with the experimental modes of vibration investigated using the Laser Doppler Vibrometer (LDV). Thus we demonstrate that the first mode at 30 kHz was indeed the optimum match.
Highlights
Micro-electromechanical Systems (MEMS) are devices and technologies that have been derived from the microelectronics industry
A method of fabricating suspended LPCVD and PECVD silicon nitride structure is demonstrated for a wide range of micro-electromechanical systems (MEMS) (Micro-Electro-Mechanical Systems) applications
Low stress LPCVD and PECVD silicon nitride film of 1 μm thickness were selected for the structure separately
Summary
Micro-electromechanical Systems (MEMS) are devices and technologies that have been derived from the microelectronics industry. The suspended structure should have optimum mechanical stress in order to obtain the structure without blister or buckle in the case of highly compressive film and without fracture in case of film having large tensile stress. These are the significant issues confronted in MEMS[1]. LPCVD silicon nitrides are mostly preferred compared to PECVD in MEMS applications because of their rigid structures which are hard enough to sustain during the wet etching process [2, 3]
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