OVERLAY CONTROL


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OVERLAY CONTROL
OVERLAY CONTROLLike critical dimension control, overlay control is a vital part of lithography in semiconductor manufacturing. Errors in the overlay of different lithographic levels can directly cause a number of electrical problems, such as short or open circuits or poor transistor performance. Overlay is defined as the positional accuracy with which a new lithographic pattern has been printed on top of an existing pattern on the wafer, measured at any point on the wafer. This is opposed to the slightly different concept of registration, which is the positional accuracy with which a lithographic pattern has been printed as compared to an absolute coordinate grid.To characterize overlay, measurement targets are placed at various spatial …
Citation
Hwaiyu Geng, CMfgE, PE: Semiconductor Manufacturing Handbook, Second Edition. OVERLAY CONTROL, Chapter (McGraw-Hill Professional, 2018 2005), AccessEngineering Export