  In this work, we briefly overview various options for Josephson junctions
which should be scalable down to nanometer range for utilization in nanoscale
digital superconducting technology. Such junctions should possess high values
of critical current, $I_c$, and normal state resistance, $R_n$. Another
requirement is the high reproducibility of the junction parameters across a
wafer in a fabrication process. We argue that Superconductor - Normal metal -
Superconductor (SN-N-NS) Josephson junction of "variable thickness bridge"
geometry is a promising choice to meet these requirements. Theoretical analysis
of SN-N-NS junction is performed in the case where the distance between the
S-electrodes is comparable to the coherence length of the N-material. The
restriction on the junction geometrical parameters providing the existence of
superconductivity in the S-electrodes is derived for the current flowing
through the junction of an order of $I_c$. The junction heating, as well as
available mechanisms for the heat removal, is analyzed. The obtained results
show that an SN-N-NS junction with a high (sub-millivolt) value of $I_cR_n$
product can be fabricated from a broadly utilized combination of materials like
Nb/Cu using well-established technological processes. The junction area can be
scaled down to that of semiconductor transistors fabricated in the frame of a
40-nm process.
