Your substrate can have a layer of contamination that isn't visible, but will prevent good adhesion and you can have rough metal. This contamination can be on the substrate prior to placing it in your deposition equipment or it can be from the deposition equipment itself. 1. Cleans: Oxidizing acid cleans are good. HF dips can be good. Resist stripper cleans should be followed by D.I. water and rinsed very thoroughly. I am always concerned about cleans that are dips in alcohols, acetone, alkanes, and aromatics. The solvent needs to be electronic grade and fresh so you don't leave a layer of organics from the solvent. The solvent itself can leave a molecular layer of itself. Having your substrate heated in vacuum can be helpful to remove organics. Descums in barrel ashers that are clean can be helpful in not only removing organics but providing bonding sites on the surface. 2. Pump Systems: Mechanical and Diffusion pumps can back stream organics. This will coat your sample and result in poor adhesion. Dry pumps are used just for that reason. Cryo pumps are great. 3. Chamber Contamination: The walls of the chamber can be a resevoir for contamination. You might want to have the chamber heated up under pump down and baked out for an hour before loading your samples. Make sure your carriers are clean and baked out as well. It might be a good idea to have a leak up rate done weekly on the chamber as well. 4. Wrong Lubrication: Sometimes a grease can be used that isn't a vacuum grease. For a vacuum system it would be preferable to have no grease. 5. Wrong O-rings: The O-ring may have been handy when someone did a repair but it is outgassing like crazy. 6. Substrate: Is it really a solid substrate or is it something that isn't 100% solid, or can have outdiffusion. Some ceramic parts look solid but they have some small percentage void space. Plastics and other seemingly solid materials may outgas. The solution would be to have a sit time for 10 to 30 minutes to allow outgass. Don't start deposition just because you reach base pressure. Your pumping speed could outpace the outgassing of your substrate but you still have a need to degass your part. 7. Target cleanliness: Was it cleaned before installation and baked out? Edward Sebesta Independent Semiconductor and MEMS Engineer. -----Original Message----- From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On Behalf Of Yinyan Gong Sent: Monday, January 19, 2009 9:34 AM To: mems-talk@memsnet.org Subject: [mems-talk] Deposition of Chromium and Platinum Dear All, I have a hard time to deposit Chromium (50nm) followed by Platinum (100nm) using a e-beam evaporator. After lift-off (using 1165), some areas of the metal layer will peel off and the rest part has very rough surface. I note that during deposition of Pt, the temperatures is quite high and I have to interrupt the deposition when the temperature reaches 90C and let the system cool down before depositing again. Any suggestions will be appreciated. Best regards Yinyan