System and method for controlling the firing of a source laser in an LPP EUV light source

摘要

A method and system for improving the timing of a source laser in a laser produced plasma (LPP) extreme ultraviolet (EUV) generation system is disclosed. Due to forces in the plasma chamber, the velocity of the droplet may decrease as the droplet approaches the irradiated site. Since the speed of the droplet is reduced, the source laser is fired quickly for the reduced speed droplet, and as a result, only the front portion of the droplet is irradiated. The amount of EUV energy generated from the resulting droplet is proportional to the reduced droplet velocity. In order to correct, the firing of the source laser for the next droplet is delayed based on the EUV energy generated. Because the source laser firing on the next droplet is delayed, the next droplet is more likely to be illuminated more fully at the right location, resulting in more EUV energy generated from the next droplet Become. [Selection] Figure 3