fibDAC stress relief - A novel stress measurement approach with high spatial resolution

fibDAC stress relief is a new method developed to measure stresses on micro and nanotechnology devices. The classical macroscopic technique of stress relief by material removal has been adopted to determine stress with very high spatial resolution and marginal restrictions regarding the material under test. Focused Ion Beam (FIB) milling is used to remove locally material. Cross correlation algorithms on high resolution SEM images captured in the same FIB equipment reveal tiny stress relief deformations. Their analysis allows computation of stresses present at the place of ion milling. Thorough qualification of the approach resulted in a stress measurement accuracy of 1-5·10-4E, where E is the Young's modulus of the material tested. Lateral resolution of stresses can be reduced to a value around 200 ... 500 nm. Although the method needs finite element stress modeling, it is free of basic assumption upon the kind of stress and the stress built-up history.