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Proceedings Paper

Investigation of the effects of charging in SEM-based CD metrology
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Paper Abstract

Scanning electron microscopes are considered the most likely tool for future CD metrology down to 0.1 micron linewidths and below. Charging effects on insulating materials are a long standing problem for electron microscopes. The shrinking design rules are making the measurement errors caused by charging more significant. In this paper a model is proposed which incorporates charging effects into a Monte Carlo simulation model. The model stems from the notion of beam induced conductivity, an established phenomenon whereby an insulator becomes conducting for a brief period of time after being hit by a primary electron. The insulator becomes conducting only within the interaction volume of the primary electron. So after multiple scans of the primary beam has occurred, it can be expected that because of the transient beam induced conductivity that the resulting charge distribution will be such a to create an equipotential surface where significant primary beam dose has occurred. This concept is applied to resist by treating the top region of the resist as a negatively charged potentials. The substrate is given a different potential In general different materials can be expected to have different potentials. One important consequence is that the corners of the resist line, if they are sharp, have strong electric fields and they repel the beam electron. We calculate the electrostatic fields given the resist geometry,then we calculate the beam deflection caused by this field, we remap Monte Carlo simulation data to fold in this effect, and finally we compare with some experimental data to see if this charging effect can account for the apparent resolution degradation that occurs at the edges of resist lines with scanning electron microscopes.

Paper Details

Date Published: 7 July 1997
PDF: 17 pages
Proc. SPIE 3050, Metrology, Inspection, and Process Control for Microlithography XI, (7 July 1997); doi: 10.1117/12.275912
Show Author Affiliations
Mark P. Davidson, Spectel Co. (United States)
Neal T. Sullivan, Digital Equipment Corp. (United States)

Published in SPIE Proceedings Vol. 3050:
Metrology, Inspection, and Process Control for Microlithography XI
Susan K. Jones, Editor(s)

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