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Proceedings Paper

New nondestructive method to measure metal film thickness
Author(s): Xiaodong Wu; Gordon S. Kino
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Paper Abstract

We report here a new, noncontacting, and nondestructive photothermal phase microscope to measure metal film thickness in integrated circuit devices down to 150 angstroms with a 30 angstroms sensitivity. A thermal diffusion wave ranging from 3 - 500 MHz is excited with an intensity modulated laser beam. The wave is reflected by the insulating layer underneath the metal film back to the surface. A second laser beam measures the reflected thermal wave using the fact that the surface reflectance is a function of the temperature. The phase delay between the surface temperature variation and the heating beam modulation yields the thickness of the opaque film. Since the technique uses the phase of the photothermal signal, instead of amplitude, the result is not critically dependent on the surface roughness or tilt of the sample. In addition, the measurement can work with very small pads (3 micrometers X 3 micrometers ).

Paper Details

Date Published: 21 May 1993
PDF: 8 pages
Proc. SPIE 1805, Submicrometer Metallization: Challenges, Opportunities, and Limitations, (21 May 1993); doi: 10.1117/12.145454
Show Author Affiliations
Xiaodong Wu, Stanford Univ. (United States)
Gordon S. Kino, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 1805:
Submicrometer Metallization: Challenges, Opportunities, and Limitations
Thomas Kwok; Takamaro Kikkawa; Krishna Shenai, Editor(s)

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