An innovative platform for high-throughput high-accuracy lithography using a single wafer stage

For 32 nm half-pitch node, double patterning is recognized as the most promising technology since some significant obstacles still remain in EUV in terms of technology and cost. This means much higher productivity and overlay performance will be required for lithography tools. This paper shows the technical features of Nikon's new immersion tool, NSR-S620 based on newly developed platform "StreamlignTM" designed for 2nm overlay, 200wph throughput and 2week setup time. The S620 is built basically upon Nikon's Tandem Stage and Local Fill Nozzle technology, but has several additional features. For excellent overlay, laser encoders with short optical path are applied for wafer stage measurement in addition to interferometers. By using this hybrid metrology, the non-linearity of the encoder scale can be easily calibrated, while eliminating the air fluctuation error of interferometer. For high throughput, a method with a new alignment microscope system and a new auto focus mapping, called Stream Alignment is introduced. It makes it possible to reduce the overhead time between the exposures remarkably. The target productivity is 4,000 wafer outs per day. Accuracy is also improved because many more alignment points and a continuous wafer height map without stitching are available. Higher acceleration and faster scan velocity of the stages are also achieved by optimal vibration dynamics design and new control system. The main body, including the projection lens, is isolated by Sky Hook Technology used already on the NSR-SF150 and SF155 steppers, and also the reticle stage is mechanically isolated from the main body. With this new platform, the imaging performance can be maximized.