Patent Number: 
Section: claims

1. A laser-plasma extreme ultraviolet (EUV) radiation source comprising: a nozzle emitting a spray of target material into a plasma generation region; and  collection optics positioned relative to the plasma generation region, said collection optics including at least one opening through which a laser beam propagates to impinge the target material and generate a plasma, said opening being positioned at a location asymmetrical relative to the collection optics so that the laser beam is directed off-axis relative to the collection optics and most of the strongest EUV radiation from the plasma reflected by the collection optics is not obscured by the nozzle. 2. The source according to  claim 1  wherein the collection optics is dish-shaped. claim 1 3. The source according to  claim 1  wherein the collection optics is a portion of a dish shape. claim 1 4. The source according to  claim 1  wherein the collection optics includes two separate openings, each receiving a separate laser beam. claim 1 5. A laser-plasma extreme ultraviolet (EUV) radiation source comprising: a nozzle emitting a spray of target material into a plasma generation region; and  collection optics positioned relative to the nozzle, said collection optics including at least one opening through which a laser beam propagates to impinge the target material and generate a plasma, said opening being positioned at a location asymmetrical relative to the collection optics so that the laser beam is directed off-axis relative to the collection optics and most of the strongest EUV radiation from the plasma reflected by the collection optics is not obscured by the nozzle but is disposed such that the angular distribution of the generated EUV radiation causes most of the strongest EUV radiation to be directed towards an edge of the collection optics. 6. A laser-plasma extreme ultraviolet (EUV) radiation source comprising: a nozzle emitting a spray of target material into a plasma generation region; and  collection optics positioned relative to the plasma generation region, said collection optics including a single opening through which a single laser beam propagates to impinge the target material and generate a plasma, said opening being positioned at a location asymmetrical relative to the collection optics so that the laser beam is directed off-axis relative to the collection optics and most of the strongest EUV radiation from the plasma reflected by the collection optics is not obscured by the nozzle. 7. A laser-plasma extreme ultraviolet (EUV) radiation source for generating EUV radiation, said source comprising: target production hardware including a nozzle, said nozzle emitting a spray of target material into a plasma generation region;  a laser beam source, said laser beam source generating a laser beam directed towards the plasma generation region; and  collection optics positioned between the laser beam source and the target production hardware, said collection optics including at least one opening through which the laser beam propagates to impinge the target material and generate a plasma, said collection optics having a shape that is at least a portion of a dish, said plasma generation region being at a focal point of the collection optics and said target production hardware being proximate the focal point of the collection optics, said opening being positioned at a location asymmetrical relative to the shape of the collection optics so that the laser beam is directed off-axis relative to the collection optics and most of the strongest EUV radiation from the plasma reflected by the collection optics is not obscured by the target production hardware. 8. A laser-plasma extreme ultraviolet (EUV) radiation source for generating EUV radiation, said source comprising: target production hardware including a nozzle, said nozzle emitting a spray of target material into a plasma generation region;  a laser beam source, said laser beam source generating a laser beam directed towards the plasma generation region; and  collection optics positioned between the laser beam source and the target production hardware, said collection optics including at least one opening through which the laser beam propagates to impinge the target material and generate a plasma, said collection optics having a shape that is at least a portion of a dish, said plasma generation region being at a focal point of the collection optics and said target production hardware being proximate the focal point of the collection optics, said opening being positioned at a location asymmetrical relative to the shape of the collection optics so that the laser beam is directed off-axis relative to the collection optics and most of the strongest EUV radiation from the plasma reflected by the collection optics is not obscured by the target production hardware and wherein the collection optics is positioned relative to the nozzle such that the angular distribution of the generated EUV radiation causes most of the strongest EUV radiation to be directed towards an edge of the collection optics. 9. The source according to  claim 8  wherein the collection optics is dish-shaped. claim 8 10. The source according to  claim 8  wherein the collection optics includes two separate openings, each receiving a separate laser beam. claim 8 11. A method of generating extreme ultraviolet (EUV) radiation, said method comprising the steps of: providing target production hardware including a nozzle;  emitting a spray of target material from the nozzle into a plasma generation region;  directing at least one laser beam to the plasma generation region to heat the target material and generate the EUV radiation; and  reflecting the generated EUV radiation from collection optics, said step of directing the laser beam including directing the laser beam through an opening in the collection optics so that the laser beam is off-axis relative to the collection optics and most of the strongest EUV radiation is not obscured by the target production hardware. 12. The method according to  claim 11  wherein the step of directing the laser beam includes directing two separate laser beams through two separate holes in the collection optics, where both laser beams are off-axis relative to the collection optics. claim 11 13. A method of generating extreme ultraviolet (EUV) radiation, said method comprising the steps of: providing target production hardware including a nozzle;  emitting a spray of target material from the nozzle into a plasma generation region;  directing at least one laser beam to the plasma generation region to heat the target material and generate the EUV radiation; and  reflecting the generated EUV radiation from collection optics, said step of directing the laser beam including directing the laser beam through an opening in the collection optics so that the laser beam is off-axis relative to the collection optics and most of the strongest EUV radiation is not obscured by the target production hardware and is reflected from an edge of the collection optics.