Droplet Stopping with Buffer Gas Debris Mitigation of EUV Source
Publication Date: 2014-Aug-20
The IP.com Prior Art Database
Protection of the NI collector and other elements inside the EUV chamber from droplets reflected from the Tin Catcher (TC) when droplets are running with no plasma being generated. The result will be increased life time of the collector. Deposition of droplet fragments is observed when the drive laser is OFF but droplet generator (DG) continues firing droplets into the TC. Some droplet fragments are backscattered by the structures of the tin catcher and travel back into the main EUV chamber. These droplet fragments or micro-droplets may fall onto the collector shortening its life time. We propose to fill the chamber for this case with a buffer gas (H2, Ar, He or other) at some pressure different from the nominal operating pressure of the source in order to stopping the reflected droplets inside the tin catcher before they can travel too far. A certain range of pressure is optimum for this purpose. It is a function of the droplet diameter, initial droplet velocity, length of the chamber, diameter and length of the tin catcher, as well as type and pressure of the buffer gas. If the gas pressure is too low (typically nominal operational pressure is too low), then droplets may leave the tin catcher after reflection. If the buffer gas pressure is too high, the droplets will be decelerated by the buffer gas and may fall short of the tin catcher and land on or be scattered onto the collector.
Page 01 of 1