Impact of lens aberrations and partial coherence on intra-field critical dimensions of dark gate lines
AbstractAcross-field variations of lens aberration and partial coherence can have undesirable effects on critical dimension (CD) uniformity and depth of focus (DOF) of printed patterns. The principal objective of this work is to investigate how lens aberrations and partial coherence variations of the light source affect critical dimensions of dark gate lines when using conventional and phase-shifting masks (PSMs) in optical projection systems.
The investigations are done using lithography simulation software tools. These advanced simulators allowed to design different optical projection system setups and diverse types of masks. This allowed to obtain diverse data which reflected the sensitivity of printed gate lines' CDs to variations of partial coherence and lens aberrations. The results are analyzed and compared suggesting guidelines to methods of maintaining a tighter control of CD errors in the manufacturing process of integrated circuits using optical lithography