Thank you to all who have replied so far to my questions I shall state a few other relevant points: 1. The Al is e-beam evaporated at a base pressure of ~ 1x10-7 mbar. Sputtering deposition tools are also available. 2. Deposition rate is 0.3 nm/s 3. The bi-layer resist thickness is 1.3 um while the metal thickness is 1um. Now I know one should always have a resist thickness at least two time greater than the metal thickness however I can add the caveat that one of the groups here at Glasgow Uni have successfully lifted off 1.2 microns Au using the same resist thickness (1.3 microns) - and they say their process is very repeatable! The problem my colleague has is he is already using the thickest e-beam resist he has available. He could probably sneak another 200 nm from spinning the resist at lower rpm which may of course aid lift-off. 4. I told him to try sonication which he has done for around 10 minutes. No joy. 5. All processing was completed within 2 days (i.e. substrate clean, resist spinning, bake, exposure, development, ashing, HF dip, Al evaporation) 6. He has not attempted to deposit thin Al I had a look at his sample for him and the metal in large areas has lifted off however in the fine feature areas (~1 um feature size) the metal has not even begun to lift-off. His next step will be to deposit 500 nm instead of 1um. I hope lift-off is more successful this time. Thanks for all your helpful comments, James Edward Sebesta wrote: > Are you using evaporation for the metal deposition? What type of metal > deposition equipment are you using. If not using evaporation for metal > deposition set parameters for poor step coverage which would be to have > the substrate cold for starters. However, given you are attempting lift > off I am assuming the substrate is unheated already. > > Also, what is the height of the bi-layer relative to the metal > thickness? > > Edward H. Sebesta > Independent Process Engineer Dr. James Paul Grant Postdoctoral Research Associate Microsystems Technology Group 76 Oakfield Avenue Room 3 University of Glasgow Glasgow Scotland G12 8LS Telephone: +44(0)141 330 3374