Method to debond an Si handler for high bow bonded wafer to wafer F2B Si Interposer
Publication Date: 2014-Sep-19
The IP.com Prior Art Database
Disclosed are method and structure that enable solvent to diffuse through a grid into the Silicon (Si) wafer handler.
Page 01 of 3
Method to debond an Si handler for high bow bonded wafer to wafer F 2B Si Interposer
For three-dimensional (3D) chip stacking, the device wafer is bonded to a temporary glass handler using a high temperature adhesive material (X2). After bonding, the full wafer is ground to remove approximately 680 um of silicon (Si). The through-silicon vias (TSVs) are exposed by removing the overlying Si. To planarize the TSV, a dielectric layer consisting of Silicon Oxygen (SiO2) and Silicon Nitride (SiN) is deposited on the wafer using the chemical-mechanical planarization (CMP) process. A seed layer of Titanium Tungsten/Copper (TiW/Cu) is applied and the images are defined by lithography. Cu is plated over the TSV surface to connect to the Back End of Line (BEOL). An SiN barrier is deposited over the Cu, and then another seed layer is set down to create the WK pad openings and Nickel/Gold (Ni/Au) is plated. After completing the WK, the bonded wafer is bonded to a second handler. The handler can be glass or Si. At this point, the wafer is flipped over to remove the first handler.
The problem with this current process is that the glass handler is expensive. In addition, during testing no more than 40 watts can be used due to the poor thermal resistance of the glass. The glass handler has very high bow when exposed to a high temperature process. An alternative process, which does not require glass, is needed.
Instead of using the glass handler, an Si wafer is used to bond to the device wafer. The glass handler can be removed with an ultra-violet (UV) laser, but this method cannot be used for the Si handler. Currently there are mechanical /thermal and laser techniques to remove the Si handler. These techniques damage the device wafer and require that the upstream bonding process use only a very low temperature adhesive material, which is not resistant to downstream dry resi...