Effects of heat curing on adhesive strength between microsized SU-8 and Si substrate

Adhesive strength between microsized SU-8 components and Si substrate is evaluated to clarify effects of heat curing. Micro-sized cylindrical shape is employed as a micro-sized adhesive test specimen to properly apply the load onto the specimen and to simply convert applied load to stress. Micro-sized cylindrical specimens of epoxy type photoresist, SU8, were fabricated on a silicon wafer using a photolithographic technique. All the load-displacement curves behave in brittle manner and all the specimens were failed from the edge of SU-8 near by the bonding interface at the maximum load. Maximum load of heat treated specimens are much higher than no heat-treated ones. Adhesive strength decreases with increasing aspect ratio of SU-8 cylinder. The decrease of adhesive strength is stronger in heat cured specimens than that without heat curing. Form the obtained results we discussed the relationship between effects of heat curing on the adhesive strength in micro-sized SU-8, Yield stress of SU-8 and the residual stress.