Patent Number: 
Section: description

The following discussion of the preferred embodiments directed to an EUV lithography source where an input laser beam is delivered off-axis relative to the first collection optics is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses. FIG. 3 is a plan view of an EUV source 66 shown at an angle similar to that of the source 50 shown in FIG. 2, according to an embodiment of the present invention. In this embodiment, target production hardware 68 is positioned at its usual location relative to a plasma spot 70. However, the collection optics 60 had been replaced with first collection optics 72 that is only partially dish-shaped and is positioned at a different location relative to the hardware 68 than the collection optics 60. In this embodiment, the collection optics 72 is about half the size of the collection optics 60, and is positioned above the target hardware 68. An opening 74 is provided in the collection optics 72 through which a target laser beam 76 propagates to the plasma spot 70. The input laser beam 76 is positioned off-axis or asymmetrical relative to the collection optics 72. Because the collection optics 72 is at this position, the angular distribution 78 of the generated EUV radiation directed towards the collection optics 72 is such that the strong EUV radiation is reflected from the upper edges of the optics 72 and is not obscured by the target hardware 68, as shown. In the embodiment shown in FIG. 3, the collection optics 72 is about one-half the size of the collection optics 60 shown in FIG. 2. Therefore, some of the generated EUV radiation does not get reflected from the collection optics 72 that normally would in the conventional system. FIG. 4 is a schematic plan view of an EUV source 82 including target hardware 84 and a plasma spot 86, according to another embodiment of the present invention. In this embodiment, first collection optics 88 has the same shape as the collection optics 60, but includes two openings 90 and 92 for two separate input laser beams 94 and 96, respectively. Basically, it is the embodiment shown in FIG. 3, only doubled so that strong EUV radiation is provided both above and below the target hardware 84. Particularly, the angular distribution 98 of the EUV radiation from the beam 94 is directed along the line of the input laser beam 94 and is reflected from the optics 88 below the target hardware 84, and the angular distribution 100 of the EUV radiation from the beam 96 is directed along the line of the input laser beam 96 and is reflected above the target hardware 84. Therefore, the embodiment shown in FIG. 4 provides more EUV radiation than the EUV source 50. The foregoing discussion describes merely exemplary embodiments of the present invention. One skilled in the art would readily recognize that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.