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Using Raman Microscopy to Detect Leaks in Micromechanical Silicon Structures

Volume 51, Number 1 (Jan. 1997) Page 123-129

Weber, W.H.; Zanini-Fisher, M.; Pelletier, M.J.

We demonstrate the use of Raman microscopy for leak detection in hermetically sealed micromachined accelerometers. Leaks were indicated by the presence of a foreign gas, in this case oxygen, in the 70- mu m-deep cavity enclosing the accelerometer between a silicon cap and a Pyrex window. Confocal, nondiffraction-limited operation of the Raman microscope utilized the available pathlength in the sample while still rejecting most of the fluorescence from the Pyrex . Raman peak intensities were accurately determined in the presence of noise by fitting the spectra to a function that modeled the unresolved Q-branch line shapes of oxygen and nitrogen.