A New Critical Dimension Metrology for Chrome-on-Glass Substrates Based ons-Parameter Measurements Extracted from Coplanar Waveguide Test Structures

Published

October 1, 2006

Author(s)

Chidubem Nwokoye, Mona E. Zaghloul, Michael W. Cresswell, Richard A. Allen, Christine E. Murabito

Abstract

In mask fabrication, Critical Dimension (CD) metrology is conducted by optical transmission, Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM) tools. All these have different advantages and limitations. The work reported here is the disclosure and simulation of an alternative metrology for extracting critical dimensions of selected features. These features are embedded in test structures that can be patterned in binary masks having absorbers of conducting material, as in the case of chrome-on-glass (COG) masks. It was undertaken as the prelude to an actual trial implementation featuring test-structure designs that have now been completed. The subject test structures are coplanar waveguides (CWG) and dimensional information is extracted from rf measurements of characteristic impedance and distributed capacitance that are made on them. Several attempts have been made previously to extract CDs from chrome-on-glass masks by DC electrical means and by capacitance measured at relatively low AC frequencies. Our preliminary e-m field modeling of characteristic impedance shows that s-parameter rf-measurements may well be suitable for extracting the CD of the signal line of a CWG. This alternative metrology has the advantage of being a non-vacuum technique and potentially that of being converted to a non-contact one. - The approach is to estimate the CDs of a selected feature by matching the CWG's as-measured characteristic impedance and distributed capacitance to values obtained from an e-m field solver. The results show that the extracted values of distributed capacitance have higher sensitivity to the CD of the signal line the larger the signal-line to ground-rail separation but that the characteristic impedance of a chrome-on-glass CWG is more sensitive to signal-line CD than the capacitance values.

Proceedings Title

SPIE

Conference Dates

September 18-22, 2006

Conference Location

Monterey, CA, USA

Conference Title

Bay Area Chrome Users'' Symposium

Pub Type

Conferences

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Keywords

", " "CD metrology, " "co-planar wave guide, " "s parameters, " "test structure, "photomask

Citation

Nwokoye, C. , Zaghloul, M. , Cresswell, M. , Allen, R. and Murabito, C. (2006), A New Critical Dimension Metrology for Chrome-on-Glass Substrates Based ons-Parameter Measurements Extracted from Coplanar Waveguide Test Structures, SPIE, Monterey, CA, USA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32422 (Accessed October 16, 2025)