A Peek Inside*

The semiconductor industry routinely fabricates device structures with feature sizes smaller than 100 nm. With millions of components crowded onto each chip and complex circuitry arrayed in three dimensions, methods to test the structures for defects--preferably nondestructively and with high throughput--become challenging. Techniques for imaging the subsurface structures tend to face a tradeoff between resolution and contrast. The probe light must have a relatively long wavelength (usually in the infrared) in order to penetrate through several millimeters of silicon in the wafer and be absorbed by the active layers of the device; however, this wavelength requirement has generally restricted lateral resolution. Ramsay et al. combine immersion lens imaging with two-photon absorption microscopy to improve both the lateral resolution and the absorption contrast, thereby providing a technique for the high-resolution three-dimensional imaging of the subsurface structures in silicon chip circuitry. -- ISO

Appl. Phys. Lett. 90, 131101 (2007).

*the above text is taken directly from - this link: http://www.sciencemag.org/content/vol316/issue5822/twil.dtl?rss=1#316/5822/174b