Wafer Scale Solventless Adhesive Bonding with iCVD Polyglycidylmethacrylate: Effects of Bonding Parameters on Adhesion Energies

Abstract

Initiated chemical vapor deposition (iCVD) polyglycidylmethacrylate (PGMA) thin films are investigated as adhesives for wafer‐scale bonding of 300 mm silicon substrates and demonstrated to form highly uniform, void‐free bond interfaces. The effects of bonding temperature and pressure on critical adhesion energy ( G c ) between iCVD PGMA and silicon are studied using the four‐point bend technique. G c values can be varied over an order of magnitude (0.59–41.6 J m −2 ) by controlling the bonding temperature and the observed dependence is attributed to changes in the physical (diffusion) and chemical (crosslinking) properties of the film. Thermal degradation studies using spectroscopic ellipsometry reveal that the iCVD PGMA films can crosslink when annealed above 120 °C in air. Further, changes in polymer behavior associated with annealing temperature are demonstrated to influence the crack propagation interface between the bonded substrates. These findings demonstrate the feasibility of iCVD polymer films for both temporary “thermoplastic,” and permanent “thermoset” bonding with potential applications in 3D integrated circuit technologies.