Hello Junjun, There are many materials that can be used for anodic bonding electrodes. My favorite is SiC because it is the most stable, the CTE is close to that of the bond stack, and is easy to clean. I think your pitting is caused by arcing. During the bond process the Na will migrate from the glass substrate into the SiC chuck. After several bonds the SiC will start to load with Na and become less conductive. This will cause arcing that can pit the chuck. You can take a multi meter and measure the resistance across the bond surface of the chuck. This resistance should be around 1Kohm. If the resistance is much over that you can clean the chuck in an RCA bath over night and it will be good as new. You can also use Di water in an ultrasonic bath at 80C over night. If you want to try other materials you can try these: Graphite: Good= very cheap, easy to machine, can be disposable Bad= Very, very dirty particle contamination can be an issue with MEMS devices, fragile, good only for a limited number of bonds, cannot be used for eutectic bonding. Stainless Steel: Good= Cheap, easy to machine, can be resurfaced Bad= Warps and needs to be resurfaced, Na pits and corrodes the surface and will need to be resurfaced. Pyrex(or Borofloat): Good= Same CTE as bond stack, Not affected by NA Bad= Expensive to machine complicated chuck, very fragile, often cracks where it mounts to bond head, cannot be used for eutectic bonding I'm a big fan of the SiC, keep it clean and it will bond your wafers forever or until a new guy smashes it in the bonder. Another trick you can try is to place a second piece of Pyrex on top of the bond stack, this will absorb some of the Na and reduce the amount of Na that get to the chuck. Give your chucks a good bath and I think you will be happy with the results.. Also check some of your old bond profiles and make sure you don't have a gross arcing issue due to bonding at the wrong pressure or not having the chuck set up properly. Good Luck, Brad Johnson Sales Application Engineer DJK Global US Distributor, Semiconductor Inspection Systems 2447 W. 12th St. - Suite 6, Tempe, AZ 85281 480-968-3343 Ext 112 office 602-501-4413 cell bjohnson@djksemi.com http://www.djksemi.com -----Original Message----- From: junjun wu [mailto:junjun@twincreekstechnologies.com] Sent: Tuesday, March 03, 2009 5:51 PM To: General MEMS discussion Subject: [mems-talk] sodium deposit corrosion in SiC electrode in anodic bonding When bonding between Pyrex and Si, it is observed that pitting occurs quickly on the SiC electrode surface against the glass surface, after a couple of bonding. It is assumed this is due to sodium deposits formed during bonding at 500V/450C. This is kind of surprising since pure SiC (not silicon rich) should show excellent resistance to alkaline corrosion. My questions are: 1. Does the SiC electrodes used in anodic bonding usually have composition other than pure SiC to have high conductivity? 2. Are there other materials that may be more resistant to alkaline corrosion, like Inconel nickel alloys, that can be used as the electrode material in anodic bonder? Thanks, Junjun Wu