Two Scanning Steppers

Featured at Semicon Europa

Nikon Precision Europe GmbH (NPE) introduces two additions to its scanning stepper family, the NSR-S202A and NSR-S102B, designed for 256M DRAM mass production. Both scanning steppers use a newly developed air guide linear motor stage that increases throughput and improves precision when compared to previous models. A reduction in alignment time has also been achieved by modifying the alignment sequence. The system designs have been integrated to ensure that mix-and-match strategies are easily accommodated.

Scanning stages are mounted on both the reticle and wafer sides and move in a synchronized manner to obtain the exposure field (25 by 33 mm). With conventional illumination systems, the exposure light passes through a rectangular slit to expose a 1:4 reduction pattern onto the wafer. The NSR-S202A uses a KrF excimer laser (wavelength 248 nm) as a light source and a lens scanning system to achieve sub-quarter micron resolution. The large 25 by 33 mm exposure area allows mass production of advanced microprocessors (MPUs) and 256M DRAMs.

Throughput improvement was achieved through two major features: the wafer stage, using the air guide linear motor that allows for faster stage movement, and the KrF excimer laser unit that shortens the exposure time. Optimizing the alignment sequence has also shortened alignment time. The NSR-S202A achieves throughput of 80 wafers per hour with 8 in. wafers. With an i-line light source (wavelength 365 nm) and a lens scanning system, the NSR-S102B achieves 0.35 micron or better resolution. The large 25 by 33 mm exposure area means less critical layers of 256M DRAMs and next-generation advanced microprocessors (MPUs) devices can be printed. As with the NSR-S202A, the new air guide linear motor stage and the enhanced alignment system improve throughput and accuracy.

Nikon Precision Europe GmbH. Paul-Ehrlich-Strasse 3-5, D-63225 Langen, F.R. Germany. Tel: (0 6103) 973-0, Fax: (0 6103) 973-304 or 973-555.