RADIATION SOURCE AND LITHOGRAPHIC APPARATUS

摘要

A radiation source includes a nozzle configured to direct a stream of fuel droplets along a droplet path towards a plasma formation location, and is configured to receive a gaussian radiation beam having gaussian intensity distribution, having a predetermined wavelength and propagating along a predetermined trajectory, and further configured to focus the radiation beam on a fuel droplet at the plasma formation location. The radiation source includes a phase plate structure including one or more phase plates. The phase plate structure has a first zone and a second zone. The zones are arranged such that radiation having the predetermined wavelength passing through the first zone and radiation having the predetermined wavelength passing through the second zone propagate along respective optical paths having different optical path lengths. A difference between the optical path lengths is an odd number of times half the predetermined wavelength.