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26 July 1999 High-speed alignment simulator for Nikon steppers
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It is an unfortunate fact that most wafer processing steps degrade the quality of the stepper alignment marks rather than improve it. One example is the severe planarization requirements used in many VLSI processes. Furthermore, process development time, especially with respect to wafer alignment, has been reduced due to fab streamlining and cost of ownership issues. With these problems in mind Nikon has developed a commercially available alignment simulator to reduce stepper usage in alignment process development. The simulator can simulate Nikon's three different wafer alignment sensor and has five different simulation modes. The simulated alignment mark can have up to ten different process layers, the thicknesses of which can be varied simultaneously if need be. In addition, the geometry of each process layer can be made quite intricate so that complicated processes can be simulate.d The simulator uses scalar diffraction theory for high speed calculations, but which is still accurate when the mark width is larger than optimization which previously took weeks can now be done in days.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Derek P. Coon, Arun A. Aiyer, Henry K. Chau, and Hiroshi Ooki "High-speed alignment simulator for Nikon steppers", Proc. SPIE 3679, Optical Microlithography XII, (26 July 1999);

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