  We present a mask aligner driven by three piezo motors which guides and
aligns a SiN shadow mask under capacitive control towards a sample surface. The
three capacitors for read out are located at the backside of the thin mask such
that the mask can be placed in $\mu$m distance from the sample surface, while
keeping it parallel to the surface. Samples and masks can be exchanged in-situ
and the mask can additionally be displaced parallel to the surface. We
demonstrate an edge sharpness of the deposited structures below 100 nm, which
is likely limited by the diffusion of the deposited Au on Si(111).
