Young´s Modulus Measurements in Standard IC CMOS Processes Using MEMS Test Structures

This letter¹ presents a method to measure the Young´s moduli of 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 were released using XeF₂ as a postprocessing 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 and 400 mum in length, with average standard deviation being 4.07 GPa.