Characterization of overlay mark fidelity

Mike Adel; Mark Ghinovker; Jorge M. Poplawski; Elyakim Kassel; Pavel Izikson; Ivan K.A. Pollentier; Philippe Leray; David W. Laidler

doi:10.1117/12.483430

2 June 2003 Characterization of overlay mark fidelity

Mike Adel, Mark Ghinovker, Jorge M. Poplawski, Elyakim Kassel, Pavel Izikson, Ivan K.A. Pollentier, Philippe Leray, David W. Laidler

Author Affiliations +

Proceedings Volume 5038, Metrology, Inspection, and Process Control for Microlithography XVII; (2003) https://doi.org/10.1117/12.483430
Event: Microlithography 2003, 2003, Santa Clara, California, United States

Abstract

In this publication we introduce a new metric for process robustness of overlay metrology in microelectronic manufacturing. By straightforward statistical analysis of overlay metrology measurements on an array of adjacent, nominally identical overlay targets the Overlay Mark Fidelity (OMF) can be estimated. We present the results of such measurements and analysis on various marks, which were patterned using a DUV scanner. The same reticle set was used to pattern wafers on different process layers and process conditions. By appropriate statistical analysis, the breakdown of the total OMF into a reticle-induced OMF component and a process induced OMF component was facilitated. We compare the OMF of traditional box-in-box overlay marks with that of new gratingbased overlay marks and show that in all cases the grating marks are superior. The reticle related OMF showed an improvement of 30 % when using the new grating-based overlay mark. Furthermore, in a series of wafers run through an STI-process with different Chemical Mechanical Polish (CMP) times, the random component of the OMF of the new grating-based overlay mark was observed to be 40% lower and 50% less sensitive to process variation compared with Box in Box marks. These two observations are interpreted as improved process robustness of the grating mark over box in box, specifically in terms of reduced site by site variations and reduced wafer to wafer variations as process conditions change over time. Overlay Mark Fidelity, as defined in this publication, is a source of overlay metrology uncertainty, which is statistically independent of the standard error contributors, i.e. precision, TIS variability, and tool to tool matching. Current overlay metrology budgeting practices do not take this into consideration when calculating total measurement uncertainty (TMU). It is proposed that this be reconsidered, given the tightness of overlay and overlay metrology budgets at the 70 nm design rule node and below.

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Mike Adel, Mark Ghinovker, Jorge M. Poplawski, Elyakim Kassel, Pavel Izikson, Ivan K.A. Pollentier, Philippe Leray, and David W. Laidler "Characterization of overlay mark fidelity", Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003); https://doi.org/10.1117/12.483430

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