Method of Timing Laser Beam Pulses to Regulate Extreme Ultraviolet Light Dosing

摘要

Described herein are embodiments of a method to control energy dose output from a laser-produced plasma extreme ultraviolet light system by adjusting timing of fired laser beam pulses. During stroboscopic firing, pulses are timed to lase droplets until a dose target of EUV has been achieved. Once accumulated EUV reaches the dose target, pulses are timed so as to not lase droplets during the remainder of the packet, and thereby prevent additional EUV light generation during those portions of the packet. In a continuous burst mode, pulses are timed to irradiate droplets until accumulated burst error meets or exceeds a threshold burst error. If accumulated burst error meets or exceeds the threshold burst error, a next pulse is timed to not irradiate a next droplet. Thus, the embodiments described herein manipulate pulse timing to obtain a constant desired dose target that can more precisely match downstream dosing requirements.

主权项

1. A method of regulating a dose of energy produced during stroboscopic firing of an EUV light source configured to generate an energy dose target within one or more packet comprising:
(a) setting by a laser controller a dose servo value for a current packet; (b) timing by the laser controller a trigger to pulse a laser beam to irradiate a droplet during the current packet; (c) sensing EUV energy generated by irradiation of the droplet; (d) accumulating by the laser controller the sensed EUV energy with EUV energy generated by irradiation of one or more preceding droplet during the current packet; (e) repeating steps (b), (c), and (d) when the accumulated EUV energy within the current packet is less than an adjusted dose target based on the energy dose target and an accumulated dose error; and (f) mistiming by the laser controller the trigger to pulse the laser beam to not irradiate another droplet during the current packet.