Title :
Tunable Properties of Hydrogenated Amorphous/Nanocrystalline Silicon Thin-Films for Enhanced MEMS Resonators Performance
Author :
Mouro, Joao ; Gualdino, Alexandra ; Chu, Virginia ; Conde, João Pedro
Author_Institution :
Inst. de Eng. de Sist. e Comput., Microsist. e Nanotecnol., Lisbon, Portugal
Abstract :
Thin-film silicon allows the fabrication of MEMS at low processing temperatures, including on large-area, low-cost, and flexible substrates. For MEMS applications, the main film properties to consider are the deposition rate, electrical conductivity, and mechanical stress. In this paper, n+-doped hydrogenated amorphous/nanocrystalline silicon thin-films are deposited by RF-PECVD. A systematic study of deposition conditions led to the identification of four different characteristic silicon thin-films, corresponding to different microstructures, with very distinct mechanical and electrical properties. These silicon thin-films are used as structural layers of electrostatically actuated thin-film MEMS bridges and cantilevers microresonators, fabricated on glass substrates at temperatures below 200 °C, using surface micromachining and thin-film technology. The effect of the mechanical stress of the structural layer (from tensile to highly compressive) on the device resonance frequency, quality factor, and required actuation forces is studied and interpreted with detailed electromechanical models.
Keywords :
Q-factor; amorphous semiconductors; cantilevers; crystal microstructure; electrical conductivity; electrostatic actuators; elemental semiconductors; microcavities; micromachining; micromechanical resonators; nanostructured materials; plasma CVD; semiconductor thin films; silicon; MEMS resonators; RF-PECVD; Si; actuation forces; cantilevers microresonators; deposition rate; electrical conductivity; electrical properties; electrostatically actuated thin-film MEMS bridges; flexible substrates; hydrogenated amorphous-nanocrystalline silicon thin-films; large-area substrates; low processing temperatures; low-cost substrates; mechanical properties; mechanical stress; microstructures; quality factor; surface micromachining; thin-film technology; tunable properties; Bridge circuits; Conductivity; Microcavities; Micromechanical devices; Resonant frequency; Silicon; Stress; Bridges subjected to axial forces; buckled bridges; deposition conditions; dissipation mechanisms; electrostatic microresonators; mechanical properties of hydrogenated silicon; quality factor; resonance frequency; surface micromachining; thin-film stress; thin-film stress.;
Journal_Title :
Microelectromechanical Systems, Journal of
DOI :
10.1109/JMEMS.2013.2286453