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|Temporary Bonding and Debonding - An Overview of Today's Materials and Methods|
|Keywords: temporary, bonding, debonding|
|Temporary bonding is a requirement for many approaches to 2.5D and 3D applications. In this presentation we will focus on the materials and methods currently available to engineers and scientists interested in temporarily bonding and debonding various substrates -- whether it be glass, silicon, sapphire, compound semiconductor and other exotics. The major classes of adhesives currently being used can be broken down into three categories: thermoplastics, thermosetting polymers and photo setting polymers. How one goes about choosing an adhesive is quite complex in nature. Thermal stability, chemical resistance, vacuum stability, bonding throughput and debonding throughput are just a few factors that must be considered when going through the selection process. All of these adhesives are typically applied by spin coating. Once the coating is completed the device wafer and temporary carrier are put into a vacuum chamber and joined. The actual bonding process depends upon the adhesive, but typically it is a thermal compression or UV curing process. To confirm the bonding process went well the bonded pair is typically checked for TTV (total thickness variation), bow, warp and voids. A deficiency in any one of these areas could severely impact yield. The debonding process also depends on the type adhesive that was used in the bonding process. Separation of the device wafer from the carrier wafer is typically achieved with one or more of the following methods: thermal softening, chemical softening, ablation, chemical dissolution, and mechanical lift-off (peeling). Typically the device wafer is released onto dicing tape and then must be cleaned. The final cleaning process, which typically is done by peeling, chemical swelling and or chemical dissolution, is equally critical as any adhesive residue trapped on or stuck to the device wafer will add to yield loss. Although at first glance temporary bonding and thin wafer handling appear to be simple, in reality they are quite complex and for this reason many different strategies are being worked on and brought to market.|
|Chris Rosenthal, Regional Product Manager