There is no more noise, only signal

by Ed Korczynski, Senior Technical Editor, Solid State Technology

In controlling the manufacturing processes used for advanced nanoscale IC, the aspects of metrology once ignored as “just noise” are now essential signals that must be controlled. Where to draw the line, and how close is “close,” are just some of the challenges in ensuring that data streams become productive information for fabs. Metrology sessions at SPIE this year shone fractional wavelengths of light into the darkness of controlling accuracy, too.

When IC features were greater than the wavelength of light used in photolithography — and likewise much greater than a countable number of physical atoms — there were many aspects of manufacturing which we could simply ignore. With the smallest IC feature, typically defined by the minimum half-pitch spacing between lines, now reaching ~45nm (which is less than one-quarter of the 193nm wavelength used in litho) we now experience “second-order” and “third-order” effects which must be controlled.

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