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Title: Intermittent-contact scanning capacitance microscopy imaging and modeling for overlay metrology

Abstract

Overlay measurements of the relative alignment between sequential layers are one of the most critical issues for integrated circuit (IC) lithography. We have implemented on an AFM platform a new intermittent-contact scanning capacitance microscopy (IC-SCM) mode that is sensitive to the tip proximity to an IC interconnect, thus making it possible to image conductive structures buried under planarized dielectric layers. Such measurements can be used to measure IC metal-to-resist lithography overlay. The AFM conductive cantilever probe oscillating in a vertical plane was driven at frequency {omega}, below resonance. By measuring the tip-to-sample capacitance, the SCM signal is obtained as the difference in capacitance, {delta}C({omega}), at the amplitude extremes. Imaging of metallization structures was obtained with a bars-in-bars aluminum structure embedded in a planarized dielectric layer 1 {mu}m thick. We have also modeled, with a two-dimensional (2D) electrostatic field simulator, IC-SCM overlay data of a metallization structure buried under a planarized dielectric having a patterned photoresist layer deposited on it. This structure, which simulates the metal-to-resist overlay between sequential IC levels, allows characterization of the technique sensitivity. The capacitance profile across identical size electrically isolated or grounded metal lines embedded in a dielectric was shown to be different. The floating linemore » shows capacitance enhancement at the line edges, with a minimum at the line center. The grounded line shows a single capacitance maximum located at the line center, with no edge enhancement. For identical line dimensions, the capacitance is significantly larger for grounded lines making them easier to image. A nonlinear regression algorithm was developed to extract line center and overlay parameters with approximately 3 nm resolution at the 95% confidence level, showing the potential of this technique for sub-micrometer critical dimension metrology. Symmetric test structures contribute to facilitate overlay data extraction.« less

Authors:
; ;  [1]
  1. Semiconductor Electronics Division, Statistical Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-0001 (United States)
Publication Date:
OSTI Identifier:
21202324
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 449; Journal Issue: 1; Conference: 1998 international conference on characterization and metrology for ULSI technology, Gaithersburg, MD (United States), 23-27 Mar 1998; Other Information: DOI: 10.1063/1.56912; (c) 1998 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALGORITHMS; ALUMINIUM; ATOMIC FORCE MICROSCOPY; CAPACITANCE; DIELECTRIC MATERIALS; EXTRACTION; IMAGES; INTEGRATED CIRCUITS; LAYERS; MASKING; NONLINEAR PROBLEMS; PROBES; RESOLUTION; RESONANCE; SENSITIVITY; THIN FILMS

Citation Formats

Mayo, S, Kopanski, J J, and Guthrie, W F. Intermittent-contact scanning capacitance microscopy imaging and modeling for overlay metrology. United States: N. p., 1998. Web. doi:10.1063/1.56912.
Mayo, S, Kopanski, J J, & Guthrie, W F. Intermittent-contact scanning capacitance microscopy imaging and modeling for overlay metrology. United States. doi:10.1063/1.56912.
Mayo, S, Kopanski, J J, and Guthrie, W F. Tue . "Intermittent-contact scanning capacitance microscopy imaging and modeling for overlay metrology". United States. doi:10.1063/1.56912.
@article{osti_21202324,
title = {Intermittent-contact scanning capacitance microscopy imaging and modeling for overlay metrology},
author = {Mayo, S and Kopanski, J J and Guthrie, W F},
abstractNote = {Overlay measurements of the relative alignment between sequential layers are one of the most critical issues for integrated circuit (IC) lithography. We have implemented on an AFM platform a new intermittent-contact scanning capacitance microscopy (IC-SCM) mode that is sensitive to the tip proximity to an IC interconnect, thus making it possible to image conductive structures buried under planarized dielectric layers. Such measurements can be used to measure IC metal-to-resist lithography overlay. The AFM conductive cantilever probe oscillating in a vertical plane was driven at frequency {omega}, below resonance. By measuring the tip-to-sample capacitance, the SCM signal is obtained as the difference in capacitance, {delta}C({omega}), at the amplitude extremes. Imaging of metallization structures was obtained with a bars-in-bars aluminum structure embedded in a planarized dielectric layer 1 {mu}m thick. We have also modeled, with a two-dimensional (2D) electrostatic field simulator, IC-SCM overlay data of a metallization structure buried under a planarized dielectric having a patterned photoresist layer deposited on it. This structure, which simulates the metal-to-resist overlay between sequential IC levels, allows characterization of the technique sensitivity. The capacitance profile across identical size electrically isolated or grounded metal lines embedded in a dielectric was shown to be different. The floating line shows capacitance enhancement at the line edges, with a minimum at the line center. The grounded line shows a single capacitance maximum located at the line center, with no edge enhancement. For identical line dimensions, the capacitance is significantly larger for grounded lines making them easier to image. A nonlinear regression algorithm was developed to extract line center and overlay parameters with approximately 3 nm resolution at the 95% confidence level, showing the potential of this technique for sub-micrometer critical dimension metrology. Symmetric test structures contribute to facilitate overlay data extraction.},
doi = {10.1063/1.56912},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 449,
place = {United States},
year = {1998},
month = {11}
}