Automated atomic force metrology applications for alternating aperture phase shift masks

With the acceptance of AAPSM's by most major semiconductor manufacturers, it is necessary to build a significant number of these masks in a cost effective and controlled manner. Optical methods of metrology used for many years in the photomask industry for binary masks are unsuitable for certain metrology applications related to AAPSM manufacture and repair. Recent work performed on a Dimension 9000M-PM automated atomic force microscope shows promise for both process control and defect review applications for AAPSM's and overcome some of the limitations of optical and SEM based metrologies. AFM metrology is shown to be able to quantify shifter step heights and phase error for features as small as 100 nm. Further, these systems are able to read in defect coordinate maps and automatically drive to these sites and scan. The scanned data provides pixel-by-pixel height data that can be used by repair tools to establish the proper dose for defect ablation.