Lightfields behind amplitude masks: Creating phase discontinuities

Shaping of light fields behind amplitude and phase masks the basis the lithographic structure reproduction. The aerial image or better the intensity distribution defines the resolution of the structure to be printed. Contrast is the main parameter and to achieve high contrast feature phase plays an important role. In our contribution we discuss the phase and intensity evolution of light fields behind different structures serving the same aim: correcting extensive corner rounding for proximity lithography. To do so we analyze the intensity characteristics behind in a binary mask having high resolution Optical Proximity Correction (OPC) at different proximity gaps and include phase evolution. The corner correction represent a two dimensional problem which is difficult to handle with simple rule based approaches. Implementation of small amplitude structures leads to sharp phase changes. The analysis has been done with an instrument called High Resolution Interference Microscopy (HRIM), a Mach - Zehnder interferometer that gives access to three dimensional phase and amplitude images.