An EUV
light source apparatus and method are disclosed, which may comprise a
pulsed laser providing
laser pulses at a selected pulse repetition rate focused at a desired target ignition site; a target formation
system providing discrete targets at a selected interval coordinated with the
laser pulse repetition rate; a target
steering system intermediate the target formation
system and the desired target ignition site; and a target
tracking system providing information about the movement of target between the target formation
system and the target
steering system, enabling the target
steering system to direct the target to the desired target ignition site. The target
tracking system may provide information enabling the creation of a
laser firing
control signal, and may comprise a droplet
detector comprising a
collimated light source directed to intersect a point on a projected delivery path of the target, having a respective oppositely disposed
light detector detecting the passage of the target through the respective point, or a
detector comprising a
linear array of a plurality of photo-sensitive elements aligned to a coordinate axis, the light from the
light source intersecting a projected delivery path of the target, at least one of the which may comprise a plane-intercept detection device. The droplet detectors may comprise a plurality of droplet detectors each operating at a different light frequency, or a camera having a
field of view and a two dimensional array of pixels imaging the
field of view. The apparatus and method may comprise an electrostatic
plasma containment apparatus providing an electric
plasma confinement field at or near a target ignition site at the time of ignition, with the target
tracking system providing a
signal enabling control of the electrostatic
plasma containment apparatus. The apparatus and method may comprise a vessel having and intermediate wall with a low pressure trap allowing passage of EUV light and maintaining a
differential pressure across the low pressure trap. The apparatus and method may comprise a magnetic
plasma confinement mechanism creating a
magnetic field in the vicinity of the target ignition site to confine the plasma to the target ignition site, which may be pulsed and may be controlled using outputs from the target tracking system.