Fin Sidewall Microroughness Measurement by AFM


The sidewalls of etched Si lines will be the carrier channel surfaces in FinFET devices. These surfaces must be as smooth as possible for optimal device performance. Thus, the ability to quantitatively measure sidewall roughness is essential to process development. A methodology to quantitatively measure Fin sidewall roughness by AFM is presented. The samples were prepared for measurement by cleaving along the length of the Fins or dense-line test structures and by FIB polishing to bring the edge of the sample close to the sidewall of the etched feature. The cleaved and FIB-polished sample was mounted 17 degrees shy of normal. This exposes the sidewall on the top surface while preventing shadowing of the lower part of the sidewall due to contact between the side of the probe support and the cleaved or polished edge. Quantitative AFM measurements taken by this method show meaningful differences in the sidewall roughness for samples that have seen different sidewall smoothing treatments. The average observed rms roughness values for various surface-smoothing treatments range from 0.8 to 1.8 Å for a 50 nm square area.

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Correspondence to Carolyn F. H. Gondran.

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Gondran, C.F.H., Morales, E., Guerry, A. et al. Fin Sidewall Microroughness Measurement by AFM. MRS Online Proceedings Library 811, 43–48 (2003).

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