A new projection lithography system is described for patterning ultra-high-density semiconductor integrated circuits. The system provides both the fine resolution and the large field size necessary for imaging the chips of the future device generations--64 Mb, 256 Mb, and beyond. The combined capabilities of high resolution and large image field are achieved by a novel scan-and-repeat exposure mechanism. Exposure of image fields as large as several inches across, while maintaining sub-half-micron resolution, is made possible by a 'seamless' scanning technique. Moreover, the above performance is achieved with today's state-of-the-art reduction lenses, thus overcoming a formidable limitation in the advancement of current optical lithography tools. The system described here can be configured with both an excimer laser source and a non-laser (lamp) source. As an example, a machine design is presented that uses a deep-ultraviolet excimer laser source, achieves the resolution and field-size performance described above, and delivers a wafer exposure throughput in the vicinity of 100 (150 mm) or 75 (200 mm) wafers/hour. These throughputs are not only several times greater than the throughput available with any other optical lithography tool. In addition to high- resolution semiconductor chip lithography, this scan-and-repeat concept is also attractive in a variety of other applications, such as flat-panel displays and electronic packaging, where seamless exposure of large areas not limited by the constraints of optical imaging systems is desirable.