Efforts to extend 193 nm lithography have introduced multiple patterning solutions to print a single level layer. Due to this increased complexity, defectivity on each layer is becoming very critical. Micro and multiple line bridges are one of the primary challenges in photolithography contributing to this complexity. These defects originate from several root causes and are difficult to eliminate. Point-of-use filtration plays a significant role on the mitigation of such defects. The impact of filtration rate and pressure was previously documented. In this research, we demonstrate that the combination of membrane and pore size selection, photoresist optimization, and hardware optimization can impact micro and multiple bridge mitigation in a 45 nm line/space pattern created through immersion lithography.
While immersion lithography has been rapidly implemented in manufacturing environments around the world, a few
defect challenges still remain. Bubble and watermark defects are well understood and have been addressed by
equipment manufacturers. However, a few defects still bewilder the lithography community, including residues and
microbridging. These defects are difficult to completely eliminate as they may have many root causes. However,
through effective point-of-use filtration, they can be greatly reduced.
Point-of-use filtration has traditionally focused on selecting a filter membrane at a specific pore size that is compatible
with the resist chemistry being utilized in the process. The research hereby discussed indicates that in addition to these
important point-of-use filter choices, careful filtration parameter setup can improve defectivity results and impact the coating process.