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Lithography k1 coefficient

Coefficient related to the difficulty of the lithography process


Each generation of integrated circuits is based on smaller geometries and this requires improved resolution from the optical lithography techniques used to draw them. The minimum feature size that a projection system can print is approximately:
MFS = k1 x lambda / NA


MFS is the minimum feature size or the critical dimension
lambda is the wavelength of light used
NA is the numerical aperture of the lens as seen from the wafer
And k1 is a coefficient that encapsulates process-related factors.

The diagram shows the trend of k1 for a range of feature sizes and some of the software techniques that have been used to extend the capabilities to smaller geometries.

Diagram courtesy of Mentor Graphics