High precision calibration of a scanning probe microscope (SPM) for pitch and overlay measurements

A general purpose SPM can function as a metrology SPM when used with a new type of calibration standard and new data analysis software. The calibration standard is a 288-nm pitch, 1-dimensional holographic grating (MOXTEK). The holographic exposure process assures uniform feature spacing over the entire specimen area, with an expected accuracy of 0.1%. We developed new software (Calibrator Pro(TM) and DiscTrack(TM)) for data analysis and used it to diagnose and correct the residual scan nonlinearity of a standard NanoScope(R) SPM. We improved the differential non-linearity of a 10 micron scan from 6.7% (range, as % of pitch) to 1.1% and we improved the integral non-linearity from 0.5% (max. error, as % of scan size) to 0.04%. We then applied the improved instrument to gauge feature spacings on magnetic disks, integrated circuits, and optical disks.