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, 1D holographic grating. The holographic exposure process assures uniform feature spacing over the entire specimen area, with an expected accuracy of 0.1 percent. We developed new software for data analysis and used it to diagnose and correct the residual scan nonlinearity of a standard NanoScope SPM. We improved the differential non- linearity of a 10 micron scan from 6.7 percent to 1.1 percent and we improved the integral non-linearity from 0.5 percent to 0.04 percent. We then applied the improved instrument to gauge feature spacing son magnetic disks, integrated circuits, and optical disks.