AIMS~(TM) and Resist Simulation

摘要

The AIMS~(TM4)5-193i is the established tool for mask performance qualification and defect printinganalysis in the mask shop under scanner conditions. Vector effects are taken into account by theproprietary Zeiss vector effect emulator. In several studies an excellent correlation to wafer prints hasbeen reported. However, a systematic offset to wafer prints in terms of mask error enhancement factor(MEEF) and exposure latitude has been observed which is attributed to well known resist effects. The AIMS~(TM)measures the aerial image in resist whereas a real lithography process further image blurof the latent image is caused by photo acid diffusion during wafer processing and resist development. Toexplain the gap between the AIMS~(TM)and wafer prints we have investigated aerial images in combinationwith an easy to use resist model. It does take resist effects into account with sufficient accuracy to explain printing behavior of photo masks but without the need to calibrate lots of parameters of theactually used resist which usually are not known to a mask shop. The resist effects predominantly reduce the image contrast and thus increase the MEEF and thesensitivity to mask defects. This somewhat counterintuitive behavior is labeled "contrast enhancementby contrast reduction". Additionally application of the resist model improves the agreement of e.g. theexposure latitude or MEEF measured by the AIMS~(TM)compared to wafer prints.