  This paper presents the design and fabrication of batch-processed cantilever
probes with electrical shielding for scanning microwave impedance microscopy.
The diameter of the tip apex, which defines the electrical resolution, is less
than 50 nm. The width of the stripline and the thicknesses of the insulation
dielectrics are optimized for a small series resistance (< 5 W) and a small
background capacitance (~ 1 pF), both critical for high sensitivity imaging on
various samples. The coaxial shielding ensures that only the probe tip
interacts with the sample. The structure of the cantilever is designed to be
symmetric to balance the stresses and thermal expansions of different layers so
that the cantilever remains straight under variable temperatures. Such shielded
cantilever probes produced in the wafer scale will facilitate enormous
applications on nanoscale dielectric and conductivity imaging.
