Two-dimensional scanning capacitance microscopy measurements of cross-sectioned very large scale integration test structures

Abstract

Scanning probe technology, with its inherent two-dimensionality, offers unique capabilities for the measurement of electrical properties on a nanoscale. We have developed a setup which uses scanning capacitance microscopy (SCM) to obtain electrical information of cross-sectioned samples while simultaneously acquiring conventional topographical atomic force microscopy (AFM) data. In an extension of our work on very large scale integration cross sections, we have now obtained one-dimensional and two-dimensional SCM data of cross sections of blanket-implanted, annealed Si wafers as well as special test structures on Si. We find excellent agreement of total implant depth obtained from SCM signals of these cross-sectioned samples with conventional secondary ion mass spectrometry (SIMS) profiles of the same samples. Although no modeling for a direct correlation between signal output and absolute concentration has yet been attempted, we have inferred quantitative dopant concentrations from correlation to SIMS depth profiles obtained on the same sample. By these means of indirect modeling, we have found that our SCM technique is sensitive to carrier density concentrations varying over several orders of magnitude, i.e., <1×1015 to 1×1020 atoms/cm3, with a lateral resolution of 20–150 nm, depending on tip and dopant level.