Impact of Spatial Coherence
The degree of coherence of the illumination source is determined by the ratio of its angular extent to the numerical aperture. This ratio is often called the partial coherence factor, or . It also affects the pattern quality and hence the application of OPC. The coherence distance in the image plane is given roughly by Two image points separated by more than this distance will effectively be uncorrelated, allowing a simpler OPC application. This distance is in fact close to the Rayleigh criterion for values of close to 1.
Read more about this topic: Optical Proximity Correction
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