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Increasing demand in technology requirements from IC manufacturers has necessitated that photolithography equipment suppliers design and build tools with many advanced capabilities. These additional features not only add to the complexity of the tools, but also increase the cost. Therefore, in order to keep lithography affordable, it is essential that equipment suppliers increase equipment productivity and extend tool lifetimes to support multiple process generations. As a further challenge, the requirements from different IC manufacturers can be quite dissimilar even for the same technology node (as defined according to the ITRS roadmap). For example, for upcoming process nodes logic manufacturers may require enhanced flexibility to enable imaging of smaller and more complicated features, coupled with tighter overlay performance. In contrast, memory manufacturers may put more emphasis on Critical Dimension Uniformity (CDU) control. Therefore, today's photolithography scanners must be equipped with the latest technologies to achieve better resolution and heightened overlay accuracy, while at the same time delivering continuous improvements to throughput. In order to extend the usable lifetime of the scanner on to next-generation technologies, the system platform must also accommodate further improvements and/or upgrades to achieve the demanding requirements of the future. In addition, the scanners must be flexible enough to integrate Complementary Technologies (CT) that are being developed in parallel to further enhance scanner performance. Litho scanner suppliers are actively addressing these issues and Nikon has developed the Sx20 platform to provide an extendible platform for dry and immersion scanner applications. Immersion scanners such as the NSR-S620D are currently being used in mass production, and support future upgrades to enable enhancements to accuracy and throughput for next-generation manufacturing. In this paper some of the key design concepts of an extendible scanner platform will be discussed. These include enhancing the accuracy and maximizing productivity of the manufacturing environment, which is vital in ensuring the affordability of lithography in the future. To show industry progress in these areas, current performance from leading edge scanners that include overlay, auto focus, and Optical Proximity Effect (OPE) matching data will be presented. In addition, it will be shown how these scanners deliver overlay accuracy sufficient for the 32 nm node and beyond, with focus uniformity less than 20nm (3σ), while utilizing a platform capable of throughput up to 200 wafers per hour. Further, to support future technology nodes, scanners also need to accommodate advanced imaging solutions such as free form illumination sources, Source Mask Optimization (SMO) and Double Pattern Techniques (DPT). Some of these technologies, as well as how they must be integrated with flexible and extendible scanner platforms in order to keep next-generation lithography affordable, will be discussed in this paper [1]. |
