Mask aligner for ultrahigh vacuum with capacitive distance control

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).