J. Kopanski, L. You, J-J Ahn, Y. Obeng
National Institute of Standards and Technology, United States
pp. 230 - 233
Keywords: nanoelectronics characterization, scanning probe microscope, sub-surface imaging
Scanning probe microscopes (SPMs) have remarkable sensitivity to the surface. The atomic force microscope (AFM) can measure surface topography and the scanning tunneling microscope (STM) can interrogate the electrical density of states, both with atomic level accuracy. SPMs also have some ability to image sub-surface structures. This paper describes the theoretical and practical basis for imaging metal lines buried beneath insulating layers and for imaging insulating regions or voids within metal with SPMs. Three techniques are discussed: scanning Kelvin force microscopy (SKFM) to image the potential of buried metal lines, scanning microwave microscopy (SMM) to image the capacitance of buried metal lines, and SMM to image voids in metals through the frequency dependence of the skin depth. A test chip, designed at NIST, and that contains buried structures to precisely produce electric potential and magnetic field variations at the surface to test the presumptions is described. COMSOL Multiphysics simulations of the surface potential due to voltages applied to buried metal lines and RF simulations of reflected microwave signals from buried metal lines were conducted and are compared to some preliminary measurement results.