AVS 49th International Symposium
    Applied Surface Science Tuesday Sessions
       Session AS-TuA

Paper AS-TuA9
Imaging Thin Oxide-Covered Metal Lines with the Photoelectron Emission Microscope*

Tuesday, November 5, 2002, 4:40 pm, Room C-106

Session: Imaging in Surface Analysis
Presenter: V.W. Ballarotto, University of Maryland
Authors: V.W. Ballarotto, University of Maryland
K. Siegrist, University of Maryland
M. Breban, University of Maryland
E.D. Williams, University of Maryland
Correspondent: Click to Email
The contrast mechanisms in photoelectron emission microscopy (PEEM) are significantly different than those in secondary electron microscopy (SEM), and thus PEEM may serve as a complementary tool to SEM in analytical applications to semiconductor device characterization. As part of an on-going study to quantify PEEM imaging response@footnote 1,2@ we have investigated imaging of metal lines buried under thin layers of silicon dioxide, including the effect of an electrical bias applied to the lines. Numerical simulations show that the lateral field strength that is generated at the edge of a metal line is the same order of magnitude as the perpendicular accelerating field strength (~10@super 6@ V/m) necessary for imaging. Therefore, electrons emitted near the edge can be displaced from the image collection volume and generate contrast. Several well-characterized samples have been used to test this contrast mechanism when imaging with and without oxide-covered metal structures. We will show images of the lateral width of the edge-contrast increasing as the bias voltage is increased from 0 to ±10 V. The magnitude of the edge effect observed for a metal line buried under 4.5 nm of SiO@sub 2@ is comparable to an uncovered metal line. Numerical studies suggest that the bias voltage necessary to minimize the edge-contrast increases about 2.5 mV per nanometer increase in height. Thus, image analysis of this effect may allow for height determination of structures. Moreover, this contrast mechanism could also be used in failure analysis by helping to identify breaks in metal lines. *Supported by LPS and in part by the NSF-MRSEC. . @FootnoteText@ @footnote 1@ V.W. Ballarotto, K. Siegrist, R.J. Phanuef and E.D. Williams, J. Appl. Phys. 91, 469 (2002).@footnote 2@ V.W. Ballarotto, K. Siegrist, R.J. Phanuef and E.D. Williams, Appl. Phys. Lett. 78, 3547 (2001).