Share Email Print
cover

Proceedings Paper

Focus and edge detection algorithms and their relevance to the development of an optical overlay calibration standard
Author(s): Stephen H. Fox; Richard M. Silver; Edward Kornegay; Mario Dagenais
Format Member Price Non-Member Price
PDF $14.40 $18.00

Paper Abstract

We present results of investigations into optical focus and edge detection algorithms relevant to overlay metrology. We compare gradient energy, standard deviation, contrast and summed intensity of acquired images as focus metrics for bright-field, scanning confocal, and confocal microscopy. For our purposes, gradient energy calculated via Sobel filtering was found to be the best criterion for an autofocus algorithm. We predict, based on theoretical results, that all of the focus algorithm we considered will focus in different heights relative to the object depending on the material properties of the object. Edge detection is accomplished via a window and spline technique for whole image data, and by application of a multiple line regression algorithm for single scan data. Measurements accomplished through these techniques are compared to state of the art scattering and analysis models.

Paper Details

Date Published: 14 June 1999
PDF: 12 pages
Proc. SPIE 3677, Metrology, Inspection, and Process Control for Microlithography XIII, (14 June 1999); doi: 10.1117/12.350794
Show Author Affiliations
Stephen H. Fox, Univ. of Maryland/College Park (United States)
Richard M. Silver, National Institute of Standards and Technology (United States)
Edward Kornegay, National Institute of Standards and Technology (United States)
Mario Dagenais, Univ. of Maryland/College Park (United States)


Published in SPIE Proceedings Vol. 3677:
Metrology, Inspection, and Process Control for Microlithography XIII
Bhanwar Singh, Editor(s)

© SPIE. Terms of Use
Back to Top