Hi everyone, We currently have some problems with the deposition of aluminium layers. Maybe some of you already experienced that phenomenon: Some bump-like structures appear all over the sample after the annealing of the evaporated Al layer (see second SEM picture). These structures seem to be empty inside however this could be the effect of the cleave. The test samples are bare silicon cleaned with solvents (opticlear, acetone and IPA, 5min each with ultra-sound). They are then immersed in a solution of 8% HF: DI to etch the native oxide (10-15sec until hydrophobicity) just before evaporation. The aluminium is then evaporated (e-beam) at a rate of 0.3nm/sec (250nm).=20 The samples surface seems very clean before the evaporation. After evaporation, the Al surface shows little protuberances (~100nm, see = first SEM picture). The 450=B0C annealing, during 30min, reveals the cavern-like structures (~500nm-1=B5m). The annealing was performed under N2 atmosphere and forming gas (N2 80%, H2 20%); both lead to the same results. We don=92t know if this comes from - a cleaning problem (traces of water or solvent at the surface before evaporation), - some problem during evaporation (contamination, non uniform deposition, stresses) amplified during annealing, - some contamination in the oven. Does anyone have any advice or suggestions? Aluminium on Si after evaporation (no annealing) Evaporated Aluminium on Si after 30min annealing at 450=B0C Thank you, Julie