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7 July 1997 Complementary alignment metrology: a visual technique for alignment monitoring
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Complementary alignment metrology (CALM) is a new metrology technique to visually measure stepper alignment correctable factors such as horizontal, vertical and rotation offsets as well as magnification errors. CALM is based on the concept that a line and space pattern exposed into resist will e completely cleared if, prior to development, it is exposed a second time by shifting the grating by exactly its half- pitch. We have used this principle to fabricate test wafers that visually indicate correctable factors. The estimated 3(sigma) accuracy of CALM readings compared to box-in-box measurements is 0.03 micrometers . Linearity between CALM readings and box-in-box measurements is maintained for misalignments of +/- 0.13 micrometers . Using such a technique allows baseline corrections to be performed on a more frequent basis.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David H. Ziger and Pierre Leroux "Complementary alignment metrology: a visual technique for alignment monitoring", Proc. SPIE 3050, Metrology, Inspection, and Process Control for Microlithography XI, (7 July 1997);

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