Preparation of photo-crosslinkable acrylic copolymer and its debonding property on silicon wafer

Abstract

As silicon wafers become thinner and easier to warp, it is important to improve production efficiency of dies. In the wafer grinding and dicing process, photo-crosslinkable pressure sensitive adhesive (PSA) tapes are applied to fix the silicon wafer and greatly increase die yield. The PSA tapes must be peeled easily without any residues after UV light irradiation. Herein, a hydroxyl group containing copolymer was first synthesized from 2-ethylhexyl acrylate, methyl methacrylate, acrylic acid and hydroxyethyl acrylate monomers via free radical polymerization, followed by the introduction of methacrylate groups through the addition reaction of 2-isocyanatoethyl methacrylate with hydroxyl groups on side chain of copolymers. The photo-crosslinkable adhesive was then prepared by the mixing the copolymers with photoinitiator and aziridine crosslinker. Glass transition temperature (Tg) and storage modulus of the photo-crosslinked adhesives increased with UV irradiation time, which benefited the picking-up process. A digital microscope was used to observe the surface morphology of the debonded silicon wafers and excellent debonding effect occurred after 40 s UV irradiation.