Die-level characterization of silicon-nitride membrane/silicon structures using resonant ultrasonic spectroscopy

Theory and experimental confirmation of a new die-level testing methodology is presented to measure physical parameters of the ubiquitous anisotropically etched silicon-nitride membrane on a silicon substrate. We have used this technique to determine the dimensions and material properties of the silicon-nitride-membrane/silicon-substrate structure (Si
_x
N/sub y//Si die) from the measured ultrasonic resonance spectra, which is obtained within seconds by the use of resonant ultrasound spectroscopy. A linear model of the changes in resonance frequencies of the structural modes to the structural dimensions and material properties is extracted using finite element analysis. Knowing this linear relationship allows one to solve the inverse problem of finding the material's characteristics and dimensions of the structure by measuring the resonance frequencies of the structure. The success in being able to measure many variables in one measurement illustrates that the method presented in this paper is viable for a fast industrial diagnosis for presorting of viable dies, or measurement for the controlled mechanical design of silicon nitride membrane structures.