Molybdenum is a common material for superconducting thin films used for example in transition edge sensors as Mo/metal bilayer. For such applications long term stability of the superconducting parameters is essential, especially the critical temperature and the transition width. Our analysis of the effect of film oxidation on these parameters for Mo/AuPd bilayers showed that even slight oxidation will have a significant effect. A direct comparison shows the potential of sidewall passivation to reduce the degradation and stabilize said parameters.