Development of an Advanced System for Automated 200 mm Wafer Mapping of Stress Using Test Structures

Controlling and understanding the stress in materials is of major importance in the successful fabrication of MEMS devices. Failure to properly account for stress related effects can lead to the substrate warping and layer delamination, both of which are detrimental to the performance and reliability of components. Hence, it is desirable to have reliable and automated technology to spatially monitor both stress and strain on silicon wafers. This paper reports in detail an integrated measurement system that has been specifically designed to semiautomatically wafer map stress, strain and Young's modulus. The measurement system is designed to determine the rotation of a test structure automatically and then calculate the strain. Young's modulus is then determined using a nanoindenter running customised software and the combination of the two measurements from the same location is used to calculate and map the spatial stress in the film.