This letter presents a method to measure the Young?s moduli of the individual thin film layers in a commercial integrated circuit (IC) foundry process. The method is based on measuring the resonance frequency of an array of micromachined cantilevers and using the presented optimization analysis to determine the elastic modulus of each layer. Arrays of cantilever test structures were fabricated in a commercial CMOS IC process and released using XeF2 as a post-processing etch. A piezoelectric transducer placed under the test chip was used to excite the cantilevers to resonance and the resonance frequency was measured using a laser Doppler vibrometer. It is reported that excellent agreement for values of Young?s modulus is observed for cantilevers between 200 um and 400 um in length with the average standard deviation being 4.07 GPa.
Citation: IEEE Electron Device Letters
Pub Type: Journals
CMOS, MEMS, residual stress, resonance, test structures, thickness measurements, Young''''''''s modulus