Galvanic corrosion of structural non-stoichiometric silicon nitride thin films and its implications on reliability of microelectromechanical devices
- Department of Electrical Engineering and Automation, Aalto University, Espoo, P.O. Box 13500, FIN-00076 Aalto (Finland)
- Department of Materials Science and Engineering, Aalto University, Espoo, P.O. Box 16200, FIN-00076 Aalto (Finland)
This paper describes a reliability assessment and failure analysis of a poly-Si/non-stoichiometric silicon nitride thin film composite structure. A set of poly-Si/SiN{sub x} thin film structures were exposed to a mixed flowing gas (MFG) environment, which simulates outdoor environments, for 90 days, and an elevated temperature and humidity (85 °C/95% R.H.) test for 140 days. The mechanical integrity of the thin films was observed to degrade during exposure to the chemically reactive atmospheres. The degree of degradation was analyzed with nanoindentation tests. Statistical analysis of the forces required to initiate a fracture in the thin films indicated degradation due to the exposure to the MFG environment in the SiN{sub x} part of the films. Scanning electron microscopy revealed a porous-like reaction layer on top of SiN{sub x}. The morphology of the reaction layer resembled that of galvanically corroded poly-Si. Transmission electron microscopy further clarified the microstructure of the reaction layer which had a complex multi-phase structure extending to depths of ∼100 nm. Furthermore, the layer was oxidized two times deeper in a 90 days MFG-tested sample compared to an untested reference. The formation of the layer is proposed to be caused by galvanic corrosion of elemental silicon in non-stoichiometric silicon nitride during hydrofluoric acid etching. The degradation is proposed to be due uncontrolled oxidation of the films during the stress tests.
- OSTI ID:
- 22490735
- Journal Information:
- Journal of Applied Physics, Vol. 117, Issue 24; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ELECTROCHEMICAL CORROSION
ENVIRONMENT
FRACTURES
HYDROFLUORIC ACID
LAYERS
MICROSTRUCTURE
MORPHOLOGY
POROUS MATERIALS
RELIABILITY
SCANNING ELECTRON MICROSCOPY
SILICON
SILICON NITRIDES
STOICHIOMETRY
STRESSES
THIN FILMS
TRANSMISSION ELECTRON MICROSCOPY