The EB stepper is an electron beam projection lithography (EPL) system. The EB stepper system is similar to an optical scanning exposure system with a reticle. Nikon has been developing EB stepper on the basis of the optical stepper design. The field size of the electron optical (EO) subsystem of EB stepper (subfield/(SF)) is 1 mm square on a reticle and 250 µm square on a wafer (demagnification: 4×). For full chip exposure, SF exposures are stitched using electron beam deflection and stage movement. A new type of stage has been developed for EB stepper using air guides and linear motors to achieve a high-throughput target. These subsystems are assembled separately at present. In this paper, preliminary results on EB stepper as an exposure system are reported. Progress on infrastructures for EPL is discussed.
Thermal analysis of projection electron beam lithography using complementary mask exposuresCompletion of the β tool and the recent progress of low energy e-beam proximity projection lithography Electron projection lithography ͑EPL͒ is one of the promising technologies below the 65 nm node, especially for contact hole and gate layers. Nikon is developing an EPL exposure tool as an electron beam ͑EB͒ stepper and the first generation EB stepper is now being manufactured. The voltage of 100 kV is adopted for electron beam acceleration. The subfield size is 0.25 mmϫ0.25 mm on the wafer and the deflection width of the electron beam is 5 mm on the wafer. The magnification of the projection optics is 1/4. A 5 mmϫ25 mm area from the 200 mm reticle can be exposed by the combination of beam deflection and stage scanning motion ͑dynamic exposure͒. This area is called ''a mechanical stripe.'' After one mechanical stripe exposure, the reticle and wafer stages turn around and the next exposure of the adjacent mechanical stripe starts as a scan and stitch stage motion. Finally, a 20 mmϫ25 mm exposure field from the 200 mm reticle is exposed. We report the first dynamic exposure in the history of EPL although only a 100 mm reticle was used. A 5 mmϫ10 mm area was used as the mechanical stripe and 10 mmϫ10 mm exposure fields were exposed. 100 nm nested lines were resolved in the entire exposure field and stitching accuracies of 17-18 nm ͑3͒ are obtained. There remain systematic errors, and stitching accuracy less than 15 nm will be achieved after fine adjustment of the subfield positions. We feel the reality of EPL is now sufficiently proven.
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