An apparatus and method for EUV light production is disclosed which may comprise a
laser produced
plasma (“LPP”)
extreme ultraviolet (“EUV”)
light source control system comprising a target
delivery system adapted to deliver moving
plasma initiation targets and an EUV light collection optic having a focus defining a desired
plasma initiation site, comprising: a target tracking and feedback
system comprising: at least one imaging device providing as an output an image of a target
stream track, wherein the target
stream track results from the imaging speed of the camera being too slow to image individual
plasma formation targets forming the target
stream imaged as the target stream track; a stream track error
detector detecting an error in the position of the target stream track in at least one axis generally perpendicular to the target stream track from a desired stream track intersecting the desired plasma
initiation site. At least one target crossing
detector may be aimed at the target track and detecting the passage of a
plasma formation target through a selected point in the target track. A drive
laser triggering mechanism utilizing an output of the target crossing
detector to determine the timing of a drive
laser trigger in order for a drive laser output pulse to intersect the plasma initiation target at a selected plasma initiation site along the target track at generally its closest approach to the desired plasma initiation site. A plasma initiation detector may be aimed at the target track and detecting the location along the target track of a plasma initiation site for a respective target. An intermediate focus illuminator may illuminate an aperture formed at the intermediate focus to image the aperture in the at least one imaging device. The at least one imaging device may be at least two imaging devices each providing an
error signal related to the separation of the target track from the vertical centerline axis of the image of the intermediate focus based upon an analysis of the image in the respective one of the at least two imaging devices. A target delivery feedback and
control system may comprise a target delivery unit; a target delivery
displacement control mechanism displacing the target delivery mechanism at least in an axis corresponding to a first
displacement error signal derived from the analysis of the image in the first imaging device and at least in an axis corresponding to a second
displacement error signal derived from the analysis of the image in the second imaging device.