Patent ID: 9497840
Filing Date: 2016-11-15
CPC Classification: H05G

Claim Text:
1. A system for timing the firing of a source laser in an extreme ultraviolet laser produced plasma (EUV LPP) light source having a droplet generator which releases a droplet at an estimated speed, the source laser firing pulses at an irradiation site, comprising: a droplet illumination module comprising a single line laser configured to generate a first laser curtain and a second laser curtain, the first and second laser curtains being of orthogonal polarizations and each located between the droplet generator and the irradiation site; a droplet detection module comprising a first sensor configured to detect a first curtain flash when the droplet passes through the first laser curtain; a first controller configured to: a second sensor configured to detect a second curtain flash when the droplet passes through the second laser curtain; and a second controller configured to determine, based upon the second curtain flash as detected by the second sensor, that the droplet is not on a desired trajectory leading to the irradiation site and providing a signal indicating an adjustment to a direction in which the droplet generator releases a subsequent droplet which will place the subsequent droplet on the desired trajectory.