An analytical approach to the impact of polarization aberration on lithographic imaging is proposed. The linear relationship between image placement error (IPE) of alternating phase-shifting mask (Alt-PSM) and odd aberration items of polarization aberrations, as well as that between best focus shift (BFS) of Alt-PSM and even aberration items of polarization aberrations are established by analytical equations, respectively. The validity of the linear relationships is demonstrated by numerical results. The differences and connections between scalar aberration and polarization aberration are briefly discussed based on these linear relationships.

To minimize the adverse effects of polarization aberrations in the projection optical system, methods to compensate the polarization aberrations are required for high resolution lithography. In this paper, we propose a symmetric polarization aberration compensation method based on scalar aberration control for lithographic projection lens. This method focuses on the compensation of polarization aberrations induced by radially symmetric retardances. The foundation of the compensation method is the linear relationship between conventional even aberration and polarization aberration induced by radially symmetric retardances. The compensation accuracy is dependent on the even aberration adjustment accuracy of the projection lens and the sensitivity of the mask pattern to even aberrations. By this polarization aberration compensation method, the lithographic process window can be improved obviously.

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