  We have performed a detailed study of the time stability and reproducibility
of sub-micron $Al/AlO_{x}/Al$ tunnel junctions, fabricated using standard
double angle shadow evaporations. We have found that by aggressively cleaning
the substrate before the evaporations, thus preventing any contamination of the
junction, we obtained perfectly stable oxide barriers. We also present
measurements on large ensembles of junctions which prove the reproducibility of
the fabrication process. The measured tunnel resistance variance in large
ensembles of identically fabricated junctions is in the range of only a few
percents. Finally, we have studied the effect of different thermal treatments
on the junction barrier. This is especially important for multiple step
fabrication processes which imply annealing the junction.
