UC San Diego

The EUV light source is a key enabler of modern photolithographic computer chip manufacture. In the light source, a high-power drive laser irradiates a tin fuel source to generate an EUV light-producing plasma. Regulation of the drive laser power is critical to ensure that the EUV light source generates the precise amount of light needed for the photolightographic process. The laser power can be adjusted by modulating the excitation medium, however, the amplification process is highly dynamic and exhibits transient behavior on short timescales. These fast timescale dynamics are important to understand as the EUV light source power must be tightly regulated. In this work, these dynamics are investigated towards the objective of developing a control system framework to regulate the drive laser power. An experiment to characterize the drive laser was carried out on a prototype drive laser system, and the results used to derive a model of the drive laser amplification process using system identification. A filtered output error model is developed which results in accurate simulation of the drive laser dynamic behavior. This model is then demonstrated to yield good performance for feed-forward control, using a model inversion framework. These results show that the modeling process is successful in generating a control-relevant model of the high power drive laser system.