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Proceedings Paper

Focused ion beam in-situ cross sectioning and metrology in lithography
Author(s): Jesse A. Salen; Drew Barnes; Gregory J. Athas; Neil J. Bassom; J. David Casey; Kathryn E. Noll; Don E. Yansen
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Paper Abstract

We demonstrate an approach to cross-section and measure sub- 0.25 micrometer photoresist profiles in both a manual and an automated fashion. This approach includes the use of a focused ion beam (FIB) system to cut small trenches through photoresist lines, leaving a clean, vertical face to measure. We demonstrate the advantage of using this process over existing techniques in the semiconductor industry. A FIB can locally cross-section the photoresist, resulting in a side- wall that is comparable to that of a mechanical cleave. It can then measure the profile of the photoresist at multiple points using a 5 nm gallium probe. The system accomplishes the entire process inside one vacuum chamber with a limited number of steps. In contrast, when using a SEM to measure profiles, the sample must be mechanically cleaved outside of the vacuum chamber, potentially destroying the entire part and leaving a slightly distorted viewing face. Also, a SEM probe can cause swelling of the photoresist due to higher currents and penetration depths than a FIB probe and must therefore be used at low accelerating voltages. When operated at these low accelerating voltages, the SEM has degraded resolution with a spot size near 10 nm. A scanning probe microscope (SPM), on the other hand, can non-destructively measure profiles, but it is slow and less automated than the FIB or SEM. Unlike a FIB, the SPM lacks the ability to image the material transition directly beneath the photoresist. We also address concerns of sample damage, gallium contamination, and image quality.

Paper Details

Date Published: 3 September 1999
PDF: 10 pages
Proc. SPIE 3882, Process, Equipment, and Materials Control in Integrated Circuit Manufacturing V, (3 September 1999); doi: 10.1117/12.361311
Show Author Affiliations
Jesse A. Salen, Micrion Corp. (United States)
Drew Barnes, Micrion Corp. (United States)
Gregory J. Athas, Micrion Corp. (United States)
Neil J. Bassom, Micrion Corp. (United States)
J. David Casey, Micrion Corp. (United States)
Kathryn E. Noll, Micrion Corp. (United States)
Don E. Yansen, Micrion Corp. (United States)

Published in SPIE Proceedings Vol. 3882:
Process, Equipment, and Materials Control in Integrated Circuit Manufacturing V
Anthony J. Toprac; Kim Dang, Editor(s)

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