The growing demands of metrology have tightened the allowable tolerances of depth and step height measurements in
semiconductor and nanotechnology fabrication. With manufacturing tolerances in the range of 1 nm to 3 nm, special
care is required to achieve calibration traceable to the SI (Systeme International d'Unites, or International System of
Units) meter in order to meet manufacturing requirements. This paper describes the steps taken to achieve this level of
measurement capability. The methodology used to achieve this traceable calibration is to use an inclined plane to
establish linearity over the step height range of interest of a reference critical dimension atomic force microscope (CDAFM)
and then to link a single traceable step height somewhere within this range. The deviations from perfect linearity
in the vertical position are shown in the paper. Then using this newly calibrated reference CD-AFM, various step height
structures were used to transfer the traceable calibration from the reference CD-AFM to one-dimensional AFMs (1DAFM)
used for manufacturing process control. A traceable step height calibration, with an expanded uncertainty of
2.24 nm (k = 3) is demonstrated for the reference CD-AFM. From this result, a traceable calibration of the
manufacturing AFMs with a combined expanded uncertainty of 2.8 nm (k = 3) for a nominal 164 nm step height is
developed.
Many semiconductor metrologists are aware that line edge roughness (LER), and thus linewidth variation (LWV), can
be a significant contributor to measurement uncertainty. More generally, the impact of measurand variation and proper
sampling is becoming a major player in nearly every area of semiconductor metrology. This paper describes a simple
technique of using the LWV of a feature as a fingerprint to uniquely characterize the measurement target in such a way
to make the LER contribution negligible in a linewidth calibration exercise. A single crystal critical dimension
reference material (SCCDRM) was the calibration artifact used to calibrate the tip width of a critical dimension atomic
force microscope (CD-AFM). These samples were released by the National Institute of Standards and Technology
(NIST) to SEMATECH member companies in 2004. The specific SCCDRM used for this work had six calibrated
linewidths ranging from 100 nm to 270 nm. Our paper shows in detail the overlay of the CD-AFM linewidth data with
that of the data used to calibrate the SCCDRM for each linewidth. With the aid of this linewidth fingerprinting, Mandel
regression is used to assess the quality of correlation of the CD-AFM to that of the NIST-derived calibration data. An
uncertainty budget is presented as a conclusion of the tip width calibration exercise. A combined expanded uncertainty
of less than 2 nm with a k = 3 coverage factor is achieved.
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