An overview of the photolithography process
The lens is used to focus the sectioned UV light down to a smaller area on the chip.
The smallest feature size capable of being written on the wafer is a function of the numerical aperture of the lens as well as the wavelength of the light.
where:
F is the smallest feature size on the chip
NA is the numerical aperture of the lens
λ is the wavelength of light
k is a coefficient accounting for process factors (usually k = 0.5)