Patent ID: 8958143
Filing Date: 2015-02-17
Classification: G03F,H01S,H05G

Abstract:
1. A method for generating EUV light by irradiating targets using at least a main pulse seed laser and a pre-pulse seed laser, comprising: determining main pulse wavelength at said targets; determining desired pre-pulse energy at said targets; iteratively testing different output wavelengths for said pre-pulse seed laser until a satisfactory output wavelength for said pre-pulse seed laser is obtained, wherein said testing involves at least one of assessing resultant pre-pulse seed energy, assessing a ratio of said pre-pulse seed energy to main pulse seed energy, and assessing chromatic-aberration related focal spot spacing, and wherein said main pulse wavelength is different from said satisfactory output wavelength for said pre-pulse seed laser; and employing said satisfactory output wavelength for said pre-pulse seed laser to generate said EUV light.