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Product Briefing Outline: KLA-Tencor and Nikon Corporation have collaborated to develop a set of fully automated overlay correction control system tools called Scanner Match Maker (SMM). Chipmakers can use the tool set to correct overlay errors common to “mix and match” lithography strategies that use lithography tools of varying capabilities and from different suppliers. The SMM technology is aimed at elevating performance of all scanners, enabling chipmakers to reduce their dedication of leading-edge scanners to specific layers, thus cutting overall lithography tool costs at more advanced nodes and extending the lifetime of lithography tools.

Problem: For most chipmakers, the high cost of latest-generation lithography tools prohibits use of the most advanced scanners on non-critical layers, resulting in different layers being exposed with different tools. Each lithography tool has a different field distortion signature that, at the small dimensions of 45nm and beyond, can cause significant overlay error. With the fully automated procedure of SMM, different illumination conditions and combinations of multiple scanners can be tightly controlled, improving productivity, operating efficiency and cost of ownership in environments using a mix of immersion and dry tools, as well as leading-edge and non-leading-edge tools.

Solution: The overlay correction procedure begins by using a common PM (planned maintenance) reticle to expose a reference wafer. The wafer is then measured by KLA-Tencor’s Archer series of overlay metrology tools and analyzed by its KT Analyzer, which collects baseline distortion signature data. The overlay data is sent to the database server. At the same time, the scanner also sends exposure condition data that is associated with the overlay metrology data, including the machine name and illumination condition. With all these data, the SMM mix and match database is created automatically with strict user approval and security. When a production lot arrives at the scanner, it requests current and previous processing layer information from the SMM database. The database server returns distortion and grid signatures from both layers. Although scanners have several functions to adjust stage grid and field distortion for matching based on PM procedures, it is not sufficient because a current layer usually has a different signature from the previous layer. Using SMM, the scanner then adjusts the distortion and grid signature using Nikon’s super distortion matching (SDM) and grid compensation matching (GCM) functions to match the target layer. GCM controls the stage grid of a current layer on the scanner, so that the grid will match with the target layer’s signature. SDM controls field distortion on a scanner’s current layer, so that field distortion will match with the target layer signature. According to the companies, testing at a major chipmaker has demonstrated greater than 30% improvement in overlay performance. Automating the procedure also increases accuracy and saves a significant amount of time. The SMM toolset enables not only mix and match among Nikon scanners but also enables mix and match with other suppliers’ lithography tools enabling greater efficiency and flexibility.

Applications: The SMM toolset enables not only mix and match among Nikon scanners but also enables mix and match with other suppliers’ lithography tools.

Platform: SMM has a built-in security system to protect each scanner suppliers’ proprietary information.

Availability: December 2007 onwards.