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Seeing Nanoscale Features with Optical Microscopes


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There are many important steps to the production of computer chips, including inspection of the chips to check on any defects. As the features on the chips reach ever smaller sizes though, new techniques are necessary for inspecting them, and some of these are hard to implement in a production line. Ideally optical microscopes would be used, because they can very quickly examine an object and now researchers at NIST have found a way to make that possible.

Due to the wavelength of light there is a limit on how small a feature can be resolved, and with visible light having wavelengths in the hundreds of nanometers it cannot be used to see the ten nanometer features on a chip. However, light will still scatter when it strikes these miniscule features and instead of ignoring this scattering, the NIST method captures that scattered light and uses it to build a picture. Scatterfield imaging works similar to CT scans by taking slices of interfering light waves and processing them into images. It also benefits from knowing what it may be looking at, so it can compare what it captures against a modeled version.

So far this method has been able to measure features on a wafer some 30 times smaller than the light's 450 nm wavelength. Next the researchers want to translate this method to ultraviolet wavelengths, which will be able to see features as small as 5 nm.

Source: NIST

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