TSOM can be used for defect analysis, inspection and process control, critical dimension metrology, photomask metrology, overlay registration metrology, nanoparticle metrology, film thickness metrology, 3-D interconnect metrology (large-range depth analysis such as through-silicon vias—TSVs), and line-edge roughness measurements.

The method uses a conventional bright field optical microscope, but rather than taking a "best focus" image, it collects 2-D images at different focal positions. A computer then extracts brightness profiles from these multiple out-of-focus images and uses the differences between them to construct the TSOM image.

This new imaging technology requires a research-quality optical microscope, a digital camera and a motorized microscope stage that can move up and down to preset distances.

"The method is relatively simple and inexpensive, has high throughput, and provides nanoscale sensitivity for 3-D measurements," says Attota. "It has the potential to save companies millions of dollars."