New low-voltage SEM technology for imaging and metrology of submicrometer contact holes and other high-aspect-ratio structures

Kevin M. Monahan; Guillermo L. Toro-Lira; Mark P. Davidson

doi:10.1117/12.148952

4 August 1993 New low-voltage SEM technology for imaging and metrology of submicrometer contact holes and other high-aspect-ratio structures

Kevin M. Monahan, Guillermo L. Toro-Lira, Mark P. Davidson

Author Affiliations +

Proceedings Volume 1926, Integrated Circuit Metrology, Inspection, and Process Control VII; (1993) https://doi.org/10.1117/12.148952
Event: SPIE'S 1993 Symposium on Microlithography, 1993, San Jose, CA, United States

Abstract

In this work we present the results of a radically different approach to imaging of high-aspect ratio structures such as contact holes. Our approach utilizes two backscattered electron detection subsystems, one optimized for imaging at the top, like most SEM detectors, and another optimized for imaging at the base of submicrometer structures. These detection systems produce signals that can be combined in real-time to produce an image which resembles the 'extended focus' images obtained with confocal optical microscopes. Unlike confocal images, however, backscattered electron images have the inherent linearity and resolution characteristic of electron-beam technology. Backscattered electron imaging has been used to solve a number of vexing problems in monitoring semiconductor process. For example, contact hole measurement with secondary electrons has typically been done with a minimum or zero signal at the base of the structure, so that the measurement value obtained either has poor precision or is the result of extrapolation. In the case of backscattered electrons, the signal can have its maximum at the base of the structure, allowing high- precision measurement with no need for extrapolation. These results are supported by extensive Monte Carlo simulations.

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Kevin M. Monahan, Guillermo L. Toro-Lira, and Mark P. Davidson "New low-voltage SEM technology for imaging and metrology of submicrometer contact holes and other high-aspect-ratio structures", Proc. SPIE 1926, Integrated Circuit Metrology, Inspection, and Process Control VII, (4 August 1993); https://doi.org/10.1117/12.148952

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