Sub-micron resolution magnetic force microscopy mapping of current paths with large probe-to-sample separation

The presence of thick over layers results in magnetic force having considerable signal-to-noise advantages over force gradient for imaging the stray magnetic fields generated by current-carrying conductors in integrated circuits. However, the longer interaction range of magnetic forces results in a considerable decrease in resolution due to coupling with the entire probe tip and cantilever. An extended model, which considers realistic magnetic force microscopy (MFM) probe geometries and the forces acting on the whole probe including along the cantilever of the probe, has been developed to show these effects. The results show that the cantilever contribution cannot be neglected. By using the difference between two images taken at different separations these effects can be largely eliminated and sub-micron resolution maps of conductor paths can be obtained at tip-to-conductor distances of greater than 2 mu m.