Systems and methods for reducing the influence of plasma-generated debris on the internal components of an EUV light source
Systems and methods are disclosed for reducing the influence of plasma generated debris on internal components of an EUV light source. In one aspect, an EUV metrology monitor is provided which may have a heater to heat an internal multi-layer filtering mirror to a temperature sufficient to remove deposited debris from the mirror. In another aspect, a device is disclosed for removing plasma generated debris from an EUV light source collector mirror having a different debris deposition rate at different zones on the collector mirror. In a particular aspect, an EUV collector mirror system may comprise a source of hydrogen to combine with Li debris to create LiH on a collector surface; and a sputtering system to sputter LiH from the collector surface. In another aspect, an apparatus for etching debris from a surface of a EUV light source collector mirror with a controlled plasma etch rate is disclosed.
1. An EUV metrology monitor for an EUV light source, said source generating debris by plasma formation, said monitor comprising:
a radiation detector;
a multi-layer mirror filtering radiation generated by the EUV light source and positioned to reflect radiation to said detector, said mirror positioned at a location wherein debris generated by plasma formation is deposited on the mirror; and
an etchant comprising H 2 to remove at least a portion the deposited debris.
2. An EUV metrology monitor as recited in claim 1 wherein said multi-layer mirror comprises at least one layer of MoSi 2 and one layer of Si.
3. An EUV metrology monitor as recited in claim 1 further comprising a metal foil filter.
4. An EUV metrology monitor as recited in claim 3 wherein said foil comprises zirconium.
5. An EUV metrology monitor as recited in claim 1 further comprising a heater selected from the group of heaters consisting of an ohmic heater, a radiative heater, a radio-frequency heater and a microwave heater.
6. An EUV metrology monitor as recited in claim 5 wherein the plasma comprises a plasma formation material, an etchant for the plasma formation material is introduced into the monitor, and the heater heats the mirror to a temperature greater than 200° C. to initiate a chemical reaction between deposited plasma formation material and the etchant.
7. An EUV metrology monitor as recited in claim 6 wherein the plasma formation material comprises Sn.