We have used a scanning SQUID microscope to image magnetic field generated
by currents in integrated circuits. To obtain current paths in these circui
ts, we apply a magnetic inversion technique to the magnetic field data. We
find that the spatial resolution obtained from this technique is related to
the signal-to-noise ratio, the SQUID-sample separation and the data sampli
ng interval. We describe in detail a mathematical model of how these parame
ters relate to the spatial resolution. Finally, we discuss the limitations
of our apparatus, and how to achieve higher spatial resolution.