  Superconducting QUantum Interference Device (SQUID) microscopy has excellent
magnetic field sensitivity, but suffers from modest spatial resolution when
compared with other scanning probes. This spatial resolution is determined by
both the size of the field sensitive area and the spacing between this area and
the sample surface. In this paper we describe scanning SQUID susceptometers
that achieve sub-micron spatial resolution while retaining a white noise floor
flux sensitivity of $\approx 2\mu\Phi_0/Hz^{1/2}$. This high spatial resolution
is accomplished by deep sub-micron feature sizes, well shielded pickup loops
fabricated using a planarized process, and a deep etch step that minimizes the
spacing between the sample surface and the SQUID pickup loop. We describe the
design, modeling, fabrication, and testing of these sensors. Although
sub-micron spatial resolution has been achieved previously in scanning SQUID
sensors, our sensors not only achieve high spatial resolution, but also have
integrated modulation coils for flux feedback, integrated field coils for
susceptibility measurements, and batch processing. They are therefore a
generally applicable tool for imaging sample magnetization, currents, and
susceptibilities with higher spatial resolution than previous susceptometers.
