Comparison of optical performances of alternative grazing incidence collector designs for EUV lithography

Two designs of grazing incidence collectors for EUV lithography are described as alternative solutions to the type I Wolter configuration. The main purposes of the designs are the improvement of collection efficiency and the increase in the flexibility with which the design can be adapted and adjusted to the boundary specifications set by the source and the illuminator. With reference to a specific scenario, examples of these designs and their performances are presented, discussed, and compared to what can be achieved with a Wolter collector. In this scenario, one of the designs offers the possibility to achieve large collection efficiency with a limited number of mirrors as opposed to the Wolter case where high values of the collection efficiency are possible provided the number of mirrors is increased.