Precise three dimensional (3D) profile measurements of vertical sidewalls of concave micro-structures are impossible by conventional profiling techniques. This paper introduces a simple technique which can obtain 3D sidewall geometry by means of laser fluorescent confocal microscopy and an intensity gradient algorithm. The measurement principle is: when a concave micro-structure is filled up with fluorescent solution, the position where the maximum intensity variation lays represents the profile of the micro-structure in the fluorescent 3D volume image. The physical essence behind this measurement principle is analyzed in this paper in detail. The strengths and limitations of this technique are studied by experiments or by illustrations. The factors that are able to improve the measurement accuracy are discussed. This technique has demonstrated the capability for measuring of 3D geometry of various concave features, such as vertical, buried and other micro channels with sub-µm (RMS) measurement accuracy and repeatability.

© 2008 Optical Society of America

1. T. Marschner, G. Eytan, and O. Dror, "Determination of best focus and exposure dose using CD-SEM side-wall imaging," Proc. SPIE 4344, 355-365 (2001). [CrossRef]
2. B. M. Rathsack, S. G. Bushman, F. G. Celii, S. F. Ayres, and R. Kris, "Inline Sidewall Angle Monitoring of Memory Capacitor Profiles," Proc. SPIE 5752, 1237-1247 (2005). [CrossRef]
3. C. G. Frase, E. Buhr, and K. Dirscherl, "CD characterization of nanostructures in SEM metrology," Meas. Sci. Technol. 18, 510-519 (2007). [CrossRef]
4. K. Miller, V. Geiszler, and D. Dawson, "Characterization and control of sub-100-nm etch and lithography processes using atomic force metrology," Proc. SPIE 5375, 1325-1330 (2004). [CrossRef]
5. A. Meyyappan, M. Klos, S. Muckenhirn, "Foot (bottom corner) measurement of a structure with SPM," Proc. SPIE 4344, 733-738 (2001). [CrossRef]
6. http://www.zeiss.com/4125681f004ca025/Contents-Frame/f5445011b5a0a89f852571d200714c4d.
7. http://www.olympusconfocal.com/applications/index.html.
8. D. L. Hitt, "Optical Considerations for Accurate Volumetric Reconstructions from 3-D Confocal Imaging," in Science, Technology & Education of Microscopy: an Overview, Vol. II, A. Mendez-Vilas, ed. (Formatex, Badajoz, Spain, 2004).
9. D. L. Hitt, "Confocal Imaging of Fluidic Interfaces in Microchannel Geometries," in Science, Technology & Education of Microscopy: an Overview,Vol.1, A. Mendez-Vilas, ed., (Formatex, Badajoz, Spain, 2003).
10. D. L. Hitt and N. Macken, "A simplified model for determining interfacial position in convergent microchannel flows," J. Fluids Eng. 126, 758-767 (2004). [CrossRef]
11. LSM 510 and LSM 510 META Laser Scanning Microscopes, Operating Manual, Carl Zeiss, 2002.
12. http://www.hi.helsinki.fi/amu/AMU%20Cf_tut/cf_tut_part1-5.htm.
13. G. B. Thomas and R. L. Finney, Calculus and Analytic Geometry, 8th ed., (Addison-Wesley, 1992) 328. [PubMed]

J. Fluids Eng.

• D. L. Hitt and N. Macken, "A simplified model for determining interfacial position in convergent microchannel flows," J. Fluids Eng. 126, 758-767 (2004). [CrossRef]

Meas. Sci. Technol.

• C. G. Frase, E. Buhr, and K. Dirscherl, "CD characterization of nanostructures in SEM metrology," Meas. Sci. Technol. 18, 510-519 (2007). [CrossRef]

Proc. SPIE

• K. Miller, V. Geiszler, and D. Dawson, "Characterization and control of sub-100-nm etch and lithography processes using atomic force metrology," Proc. SPIE 5375, 1325-1330 (2004). [CrossRef]
• A. Meyyappan, M. Klos, S. Muckenhirn, "Foot (bottom corner) measurement of a structure with SPM," Proc. SPIE 4344, 733-738 (2001). [CrossRef]
• T. Marschner, G. Eytan, and O. Dror, "Determination of best focus and exposure dose using CD-SEM side-wall imaging," Proc. SPIE 4344, 355-365 (2001). [CrossRef]
• B. M. Rathsack, S. G. Bushman, F. G. Celii, S. F. Ayres, and R. Kris, "Inline Sidewall Angle Monitoring of Memory Capacitor Profiles," Proc. SPIE 5752, 1237-1247 (2005). [CrossRef]

Other

• http://www.zeiss.com/4125681f004ca025/Contents-Frame/f5445011b5a0a89f852571d200714c4d.
• http://www.olympusconfocal.com/applications/index.html.
• D. L. Hitt, "Optical Considerations for Accurate Volumetric Reconstructions from 3-D Confocal Imaging," in Science, Technology & Education of Microscopy: an Overview, Vol. II, A. Mendez-Vilas, ed. (Formatex, Badajoz, Spain, 2004).
• D. L. Hitt, "Confocal Imaging of Fluidic Interfaces in Microchannel Geometries," in Science, Technology & Education of Microscopy: an Overview,Vol.1, A. Mendez-Vilas, ed., (Formatex, Badajoz, Spain, 2003).
• LSM 510 and LSM 510 META Laser Scanning Microscopes, Operating Manual, Carl Zeiss, 2002.
• http://www.hi.helsinki.fi/amu/AMU%20Cf_tut/cf_tut_part1-5.htm.
• G. B. Thomas and R. L. Finney, Calculus and Analytic Geometry, 8th ed., (Addison-Wesley, 1992) 328. [PubMed]

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