Photo-Imageable Dielectrics Enabling Structured MEMS and 2.5D / 3D Bonding Systems

Abstract

DuPont has developed a new Photo-Imageable Dielectric (PID) to complement its existing permanent bonding materials. The CYCLOTENEâ?¢ family of dielectric materials are well known for use as a permanent dielectric and have seen significant use in commercial applications including BSI CMOS image sensors, integrated passive devices and as an optical bonding adhesive. For new applications, there is a desire to have a thermal stable material that can be patterned to eliminate the material from the metal joining region or from the light path. We will demonstrate in this paper that the solvent developed PID as well as our existing aqueous developable PID are both capable of wafer to wafer bonding after photo imaging and development. In addition to bonding using a commercial wafer to wafer bonding tool, we have shown that wafer to wafer bonding is achievable using a two-stage vacuum laminator. Optimization of the curing process will be discussed to prevent any separation or reflow of the PID as well as achieving the maximum adhesion energy after full cure. Finally, we will show the use of the negative tone PID as a solder collar or polymer dam to enable high density flip chip bonding using 15?m Sn/Ag capped copper pillars with a 1:1.5 pitch to a and 18?m polymer openings with a 1:1.08 pitch in 10mm x 10mm dies as well as outline the process we will use to extend this approach to Cu-Cu hybrid bonding.