Determination of the tip shape is an important prerequisite for converting the various scanning probe microscopies form imaging tools into dimensional metrology tools with sufficient accuracy to meet the critical dimension measurement requirements of the semiconductor industry. Determination of the tip shape generally requires that the tip be used to image a tip characterizer. Characterizing the characterizer has itself been an obstacle to progress, since most methods require the geometry of the characterizer to be known with uncertainty small compared to the size of the tip. We have recently developed a blind reconstruction method which allows the 3-dimensional tip shape to be estimated from an image of an unknown characterizer. This method has heretofore been tested only in simulations. We report here initial results of an experimental test of the technique. We compare the reconstructed profile of a tip to an independently measured profile using a scanning electron microscope (SEM). A relatively large (500 nm radius) diamond stylus profiler tip was used in order to test the principle of blind reconstruction in a size regime where SEM instrumental uncertainties are small compared to the tip size. The blind reconstruction and SEM profiles agree well, differing only by an amount comparable to the reproducibility of the stylus profiler images (better than 2% of the sample corrugation in this instance).
Characterization and Metrology for ULSI Technology 1998 International Conference
March 1, 1998
International Conference on Characterization and Metrology for ULSI Technology