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Development of Nano-scale Deformation Measurement Techniques

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Development of nano-scale deformation measurement techniques

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Deformation measurements are needed urgently in the sub-nanometer range.  The need for nano-scale measurements becomes imminent as nanoscale components and interconnects are realized in actual devices, most notably in semiconductor devices.  The reliability of devices is determined largely by deformations of nanoscale structures during manufacturing and operation.  These are inferred by computational analysis, but informed physical analysis is vital to measure the variables and to guide and verify the computations.  What is needed is full-field in-plane displacement measurements that are accurate within a fraction of nanometers, together with sub-micron length scale.

An experimental technique to measure sub-nanometer scale in-plane deformations on a micron scale region of interest has been developed.  The Nano-Pattern Recognition and Correlation Technique (N-PRCT) utilizes regularly oriented patterns.  Displacements are obtained by tracking the movement of each pattern on the images before and after loading through pattern recognition and correlation.  The regularity offers a special benefit, relative to the random markings used in the existing techniques, which makes the proposed technique less sensitive to the random noise inherent in digital images at extreme magnifications (a region of interest less than 10 µm).  The method is implemented to document thermally-induced deformations of a microelectronics circuit.  A unique practice of E-beam lithography using a standard SEM is proposed and implemented to fabricate regularly oriented patterns required for N-PRCT.  The patterns are produced on a polished cross-section of a flip-chip package, and the package is subsequently subjected to a temperature excursion inside the SEM chamber.  Thermal deformations with the displacement measurement accuracy of 0.1 nm are obtained in a region of interest of approximately 7×6 µm.

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