ECEN 4616/5616
1/28/2013
Typical design for a Lithographic lens for imaging masks on computer chips:
Features from first-order analysis:
1. Field curvature controlled by having equal amounts of positive and
negative powers.
a. Net positive power assured by arranging the negative lenses where
ℎ
ℎ
the marginal rays are low. (𝐾 = 𝐾1 + ℎ2 𝐾2 + ℎ3 𝐾3 + ⋯
1
1
2. Spherical aberration minimized by using many lenses at low incident
angles. Total spherical eliminated by balancing negative and positive lens
contributions.
3. High (de)magnification (from the mask to the chip) achieved through
multiple sets of lens groups.
Typical size of these lenses: 1ft X 3 ft
Typical cost of these lenses: ~$30,000,000