Quantitative Kelvin probe force microscopy imaging on locally doped semiconductors

Failure analysis and optimization of nanoelectronic devices demand knowledge of their electrical properties. Especially, quantitative profiling of dopant concentrations is essential for process and device engineering in semiconductor industry. The most straightforward nanometrology technique is the Kelvin probe force microscopy (KPFM) where electrostatic forces are detected.
Quantitative dopant profiling by means of KPFM measurements is successfully shown on a conventional static random access memory (SRAM) cell and on
cross-sectionally prepared Si epilayer structures by applying a recently introduced new explanation of the measured KPFM signal [1]. The presented KPFM model is also used to explain observed large conductivity differences in different pulsed laser annealed Mn-implanted Ge samples by revealing a strong variation of the Fermi level position on the micrometer scale in dependence on
the annealing conditions after Mn implantation [2].
In addition, the frequency dependence of the KPFM bias is discussed. Using an active mixer, the excitation amplitude of the cantilever is almost independent of the operation frequency. As a result, the frequency dependence is samplespecific and KPFM measurements have to be performed at frequencies high enough so that the electrical properties of the locally doped semiconductor are
probed.

[1] C. Baumgart, M. Helm, H. Schmidt, Phys. Rev. B 80, 085305 (2009).
[2] S. Zhou, D. Bürger, A. Mücklich, C. Baumgart, W. Skorupa, C. Timm, P. Oesterlin, M. Helm,
and H. Schmidt, Phys. Rev. B 81 (2010), 165204.