VLSI_Class_Notes_13_2010

VLSI_Class_Notes_13_2010 - EEL 5322 W.R.Eisenstadt -1- VLSI...

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EEL 5322 W.R.Eisenstadt - 1 - VLSI Class Notes Fall 2010, Class 13 Lecture discussion : Photolithography continued 5) Step and Repeat Systems: See attached Generic Photolithography optical system The step and repeat system is an alignment and exposure system that exposes photoresist to light. This system typically works with monochromatic light. It prints one die or one chip at a time. The image is scanned across the wafer, chip-by-chip. This system reduces the IC printed image 4x, 5x or 10x less than the Reticle pattern size on the mask Definition: N.A = Numerical Aperture, a parameter which reports a lens system s ability to collect light. For light refracted in the condenser lens, N.A. = n sin a , in which n is the refractive index, For air n=1 3 5 3 5 2 sin tan 6 5! 3 15 a @ - + @ - + @ L , for a small 2 tan 2 D f = For an air dielectric: n= 1 2 . . 2 D N A f = (1.1) in which D is the diameter of the lens and f 2 is the focal plane distance from the condenser lens to the wafer. See attached diffraction diagrams
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VLSI_Class_Notes_13_2010 - EEL 5322 W.R.Eisenstadt -1- VLSI...

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