Progress of a laser plasma EUV light source for lithography

Realization of an extreme ultraviolet (EUV) light source with sufficient output power and lifetime is one of the critical issues for EUV output power of 115 W and a pulse energy stability of ±0.3% (3σ, 50 pulses integral) in order to enable throughput of 100 wafer/hour and to achieve uniform dosage control. A collector mirror with long lifetime is also required to the minimize operation cost. Key issues for the source development to realize these requirements are as follows: improvement of the cost conversion efficiency from input YAG laser to the output EUV power; laser parameter optimization for the target; high repetition rate operation of more than 10 kHz for the EUV pulse stability improvement; and evaluation of the collector mirror damage mechanism for the long life mirror technology development. In this paper, the progress of laser produced plasma EUV light source development status for lithography technology is reported. In order to realize the light source requirements to achieve sufficient output power and lifetime, this study focuses on the development of the EUV light source in response to the key issues previously mentioned.