Directed gas purge to reduce dusting of excimer discharge chamber windows

A light source apparatus comprising:

• a chamber configured to hold a gas discharge medium, the gas discharge medium outputting a light beam;
• a metal fluoride trap coupled to the chamber and configured to trap metal fluoride dust generated from the chamber and provide clean gas along an output port;
• and
• a set of window housing apparatuses coupled to the chamber and configured to reduce metal fluoride dusting on optical windows, wherein each window housing apparatus comprises:
• a window housing supporting an optical window;
• an aperture apparatus coupled to the window housing and comprising a plurality of cells configured to trap metal fluoride dust flowing upstream from the chamber through the aperture apparatus toward the optical window;
• and
• an insert disposed between the aperture apparatus and the optical window, wherein the insert is configured to control a first flow rate of the clean gas along the optical window and a second flow rate of the clean gas through the aperture apparatus, wherein the insert is configured such that the first flow rate along the optical window is greater than or equal to the second flow rate through the aperture apparatus.

A window housing apparatus configured to reduce metal fluoride dusting on an optical window, the window housing apparatus comprising:

• a window housing supporting the optical window;
• an aperture apparatus coupled to the window housing and comprising a plurality of cells configured to trap metal fluoride dust flowing through the aperture apparatus toward the optical window;
• and
• an insert disposed between the aperture apparatus and the optical window, the insert defining an insert port fluidly coupling a flow distribution around the aperture apparatus with a channel defined in the window housing;
• wherein the insert is configured to control a first flow rate of clean gas along the optical window and a second flow rate of the clean gas through the aperture apparatus.

A window housing apparatus configured to reduce metal fluoride dusting on an optical window, the window housing apparatus comprising:

• a window housing supporting the optical window;
• an aperture apparatus coupled to the window housing and comprising a plurality of cells configured to trap metal fluoride dust flowing through the aperture apparatus toward the optical window;
• and
• an insert disposed between the aperture apparatus and the optical window, the insert configured to control a first flow rate of clean gas along the optical window and a second flow rate of the clean gas through the aperture apparatus;
• wherein a plurality of tangs are disposed along an exterior surface of the aperture apparatus and are configured to direct the clean gas to flow around the aperture apparatus toward the insert, wherein the plurality of tangs are symmetrically arranged.

A window housing apparatus configured to reduce metal fluoride dusting on an optical window, the window housing apparatus comprising:

• a window housing supporting the optical window;
• an aperture apparatus coupled to the window housing and comprising a plurality of cells configured to trap metal fluoride dust flowing through the aperture apparatus toward the optical window;
• and
• an insert disposed between the aperture apparatus and the optical window, the insert configured to control a first flow rate of clean gas along the optical window and a second flow rate of the clean gas through the aperture apparatus;
• wherein the window housing apparatus is configured such that the first flow rate along the optical window is greater than or equal to the second flow rate through the aperture apparatus.

A method of reducing metal fluoride dusting on an optical window in a window housing apparatus, the method comprising:

• directing clean gas to flow from a metal fluoride trap through an input port of the window housing apparatus;
• directing the clean gas to flow around an aperture apparatus disposed in a window housing of the window housing apparatus and toward an insert disposed between the aperture apparatus and the optical window;
• directing the clean gas to flow through a channel in the window housing and along an interior surface of the optical window;
• and
• directing the clean gas to flow from the optical window through the aperture apparatus,
• wherein the directing the clean gas to flow around the aperture apparatus comprises directing the clean gas to flow through an insert channel in the insert.