Full-Field Exposure Tools for ArF Immersion Lithography

摘要

Immersion lithography has by far satisfied most expectations regarding its feasibility as the next lithographic technique for the 65-nm node and below. To further advance 193-nm immersion lithography, a means of efficiently controlling water as an immersion fluid and research and development concerning resist processes are necessary. In 2004, Nikon Corporation introduced a 0.85 numerical aperture (NA) 193-nm immersion exposure tool that uses water as the immersion liquid. This engineering evaluation tool (EET) is equipped with a highly efficient temperature-stabilized water nozzle assembly. Selete Inc. in collaboration with Nikon Corporation has been evaluating the performance and various characteristics of the EET while also investigating various photoresist and topcoat processes. We selected three types of standard immersion processes that offered the best performance for our evaluation purposes. A resolution limit of 70-nm half-pitch line-and-space (L/S) patterns has been confirmed. A 0.8-μm depth of focus (DOF) was also verified for an 80-nm half-pitch L/S pattern. In addition, full wafer (WF) critical dimension (CD) uniformity of less than 5 nm (3 sigma) has been demonstrated for a 90-nm half-pitch L/S pattern on a 300-mm wafer (WF). After the implementation of various improvements to both the EET and the topcoat/resist processes, we have achieved a total defect density of 0.23/cm~2, and this defect level is low enough for pilot production.