Electrical scanning probe microscopy techniques for the detailed characterization of high-k dielectric layers

The use of scanning probe microscopy (SPM) techniques for the electrical characterization of high-k dielectric layers is reviewed, focusing on conductive atomic force microscopy (cAFM) and scanning capacitance microscopy (SCM). It is demonstrated exemplarily for ZrO2 high-k layer stacks that cAFM enables a detailed analysis of the morphological and electrical layer characteristics. Film morphologies can be determined even for surfaces where topography mapping can not detect distinct surface roughness like grain structures. For as-deposited amorphous layers, the current distribution is random whereas increased leakage currents at grain boundaries can be observed for nano-crystalline samples. The dominant current mechanisms through the layers can be determined from current voltage curves at distinct local points. Comparison with conventional techniques proofs the findings by cAFM. The quantitative interpretation of SCM measurement results often suffers from parasitic capacitances and light induced effects. Local thickness variation of dielectrics, however, can be detected very sensitively.