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.

Microsphere-assisted microscopy: challenges and opportunities

“…Furthermore, the QPM techniques promoted by MAM can easily be integrated with other resolution-enhancing methods like structured and oblique illumination, enabling even further enhancements in resolution [47,48]. Microsphere-assisted interference microscopy brings forward a cost-effective and non-destructive high-speed single-shot technique for 3D surface metrology [12,49,50]. On the other hand, microsphere-assisted digital holographic microscopy (DHM) offers a real-time approach for high-contrast QPM in both transmission and reflection modes [17,51].…”

Simulative investigation of microcylinder-assisted microscopy in reflection and transmission mode

“…Generally, it should be mentioned that microspheres are usually applied in experimental studies due to the resolution enhancement in both lateral directions, whereas microcylinders are more often considered in theoretical studies for computational reasons. Further, MAM can be combined with other techniques such as confocal, 11,12 interference [13][14][15] or fluorescence microscopy 16,17 to enhance the lateral or axial resolution. Despite many investigations, the major reason for the obtained resolution enhancement is not clearly clarified yet.…”

Polarization dependency of the 3D transfer behavior in microsphere enhanced interferometry

“…With the ongoing trend towards miniaturization overcoming Abbe's diffraction limit in optical metrology is of particular interest regarding research and industrial applications. Microsphere assistance as a near-field support is investigated as a technique to realize topographical interferometric [1][2][3] as well as microscopic [4][5][6] measurements of structures below the resolution limit. Photonic nanojets are mentioned frequently to be the decisive mechanism [7][8][9].…”