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Proceedings Paper

Comparison and uncertainties of standards for critical dimension atomic force microscope tip width calibration
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Paper Abstract

Since the advent of critical-dimension atomic force microscopes (CD-AFMs) in the 90s, these tools have enjoyed growing acceptance in semiconductor manufacturing both for process development and to support in-line critical dimension (CD) metrology. The most common application of CD-AFMs has been to support critical-dimension scanning electron microscope (CD-SEM) and scatterometer metrology as a reference for tool matching or as a nondestructive alternative to transmission electron microscopy (TEM) and scanning electron microscopy (SEM) cross sections. For many years, CD-AFM users typically developed in-house reference standards for tip width calibration - often based on SEM or TEM cross sections. But the uncertainty of such standards was often large or unknown. Tip characterizer samples - which used a sharp ridge to calibrate the tip width - are commercially available. However, scanning such samples can result in tip damage, and the uncertainty of tip calibrations based on this method is at least 5 nm. In 2004, NIST, SEMATECH, and VLSI Standards collaborated on the development and release of single crystal critical dimension reference materials (SCCDRMs) to SEMATECH member companies. These specimens, which are fabricated using a lattice-plane-selective etch on (110) silicon, exhibit near vertical sidewalls and high uniformity and can be used to calibrate CD-AFM tip width to approximately 1 nm standard uncertainty (k = 1). Also in 2004, commercial critical dimension standards (CCDS) were introduced. Using CD-AFM instruments at both NIST and SEMATECH, we have performed a comparison of nominal 45 nm and 70 nm CCDS specimens with the SCCDRM calibration. Our observations show that these two independently performed calibrations are in agreement.

Paper Details

Date Published: 5 April 2007
PDF: 11 pages
Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 651816 (5 April 2007); doi: 10.1117/12.714032
Show Author Affiliations
Ronald Dixson, National Institute of Standards and Technology (United States)
Ndubuisi G. Orji, National Institute of Standards and Technology (United States)


Published in SPIE Proceedings Vol. 6518:
Metrology, Inspection, and Process Control for Microlithography XXI
Chas N. Archie, Editor(s)

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