To make transistors and other circuit elements that are very...

To make transistors and other circuit elements that are very small, modern integrated circuits (like those used in a computer) are produced using very high resolution optical patterning. The process uses a very expensive lens to produce the pattern. If the smallest circuit feature size is 200 nm, what does the Rayleigh criterion predict for the approximate wavelength of the light used to make the pattern? How does that compare with the wavelength of blue light?

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Key Concepts

Rayleigh Criterion

The Rayleigh criterion defines the diffraction limit of an optical system, stating that two point sources are just resolvable when the principal diffraction maximum of one image coincides with the first minimum of the other. This sets a basic limit on the smallest feature size that can be resolved, directly linking resolution to the wavelength of light and the numerical aperture of the lens used.

Optical Lithography

Optical lithography is a manufacturing process used in the production of integrated circuits where patterns are transferred onto a substrate using light. Its resolution is constrained by the diffraction limit as described by the Rayleigh criterion, which means that to print very small features, the process requires light of a shorter wavelength.

Wavelength Comparison

In the context of optical resolution, shorter wavelengths allow for finer detail to be resolved. For instance, if the smallest feature size is around 200 nm, the light used must have a wavelength in the deep ultraviolet range, which is significantly shorter than that of blue light (approximately 450-495 nm). This comparison highlights why deep ultraviolet light is preferred for fabricating very small circuit elements.

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