Hello Lin, You have found the limitations of a home built bonder. Applying heat and force to your sample are the easy part, applying it uniformly is the hard part. That is why companies like SUSS MicroTec and EVG charge so much for a tool that "gets hot and pushes hard", there is a lot of engineering in these tools. There isn’t any easy solution to your very general question but try this: 1. I am assuming you are doing a Si/Si fusion bond. If this is the case then you can try to start the bond when you do the alignment by pressing the wafer together with your fingers. If your bond surface is of high quality then the bond should propagate across the wafer. Even if you get a small area of local bonding this should hold the wafers in place while in the bonder. If you have a good Van Der Waals bond before entering the bonder the alignment should not change if it does then you should look at either redesigning your bonder or just skipping the bonder all together and going to the anneal oven. If you have a good Van Der Waals bond you do not need to add force during the anneal step. 2. You can try putting some graphite foil sheets under the sample to see if that helps to even out the force load and help reduce the shifting. Sheets of 500um to 1000um should help. Check out the book "Semiconductor Wafer Bonding Science and Technology" by Q.Y. Tong and U.Gosele ISBN 0-471-57481-3 it has all of the basic info you need to get your wafers stuck together. 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: Lin Yu [mailto:hinet.cnt@gmail.com] Sent: Tuesday, September 02, 2008 12:59 PM To: mems-talk@memsnet.org Subject: [mems-talk] Thermal bonding problem Hello all, I was doing some research of bonding two initially aligned Si pieces. A homemade thermal bonder has been used, which can provide force and heat the samples. However, due to the shear force generated by the bonder head on the samples, the initial alignment was broken during the bonding. Is there any way that I can reduce the shear force to avoid breaking the alignment? Any suggestion is appreciated. Thanks, Lin