Abstract: Novel local curvature test structures combined with a sub-nanometer optical interferometry measurement setup are developed to detect stresses in nanometer-scale films and ultra low stresses in thin films.Several "localized" test structures based on the bending plate measurement method are designed to improve its sensitivity and accuracy.FEM analysis is performed to calculate the deviation of boundary-introduced stress from that predicted by the Stoney formula.Optimized structures are fabricated with anisotropic etching and DRIE.Stress values obtained with this metrology are in good agreement with those extracted by other methods,and repeatability within 1% is achieved.Stress differences as small as 1.5MPa in the 30nm film can be resolved.Such resolution is among the finest in the world.

Key words: MEMS, internal stress, nano-film, bending-plate measuring methodology, optical interferometry measurement