High Resolution Surface Metrology Using Microsphere‐Assisted Interference Microscopy

Abstract

The authors review some of the latest results of a new high resolution optical metrology technique using small glass microspheres placed on the sample to enhance the lateral resolution in optical microscopy. Experimental results are shown of high resolution 2D images of gratings and microelectronic structures. The results of simulations and experimental measurements for 2D imaging through glass microspheres show an increase in magnification of 3–5 times and a lateral resolution as small as 100 nm in air. Experimental results are also shown of 3D measurements of different nanostructures using microspheres that have successfully been incorporated into Mirau and Linnik type interferometers. Results are shown on grooves in Blu‐Ray discs, narrow etched gratings in Si, nanotextured stainless steel surfaces, and on Ag nanodots. Measurements using SEM and AFM are given for comparison. Some of the artefacts and sources of errors in the microsphere‐assisted measurements are presented and discussed. The authors thus demonstrate that microsphere‐assisted interference microscopy is a promising new optical tool for nanometrology.