A method of polarization-mode conversion based on birefringent film in immersion lithographic illumination system

摘要

In immersion lithographic illumination system, appropriate polarization illumination can improve the resolution andimaging quality. Thus it is of great significance to realize different polarization-modes. The zero-order half-wave platesare usually used to achieve conversion of different polarization-modes. However, large-diameter zero-order half-waveplate is too thin to manufacture and assembling. This paper presents a polarization-modes conversion method based onbirefringent film. The properties of birefringence film is similar to zero-order half-wave plate, and the film is easy tomanufacture. Theoretically, it can be estimated that the film thickness is 2.4μm correspond to 180° retardation in 193nmwavelength. The experiment indicates that the 180° birefringent film can convert linear polarization-modes successfully,which verifies the feasibility of the film as a substitute of zero-order half-wave plate in immersion lithographic illuminationsystem. The method solves the problem that it is difficult to manufacture large-diameter zero-order half-wave plates, andprovide a reference for the design of lithographic illumination system.