Evolution of residual stress in benzocyclobutene films with temperature

Abstract

Benzocyclobutene (BCB) is widely used for wafer level packaging of radio frequency micro-electro-mechanical system (RF MEMS) devices. Although BCB is spin-coated at room temperature, its prebaking, post baking and subsequent processing may induce residual stresses. This work intends to investigate the stress–temperature behaviour of BCB films. In these experiments, the residual stress values are found to be tensile in nature. As coated BCB film is found to possess a minimal stress (3MPa); while it maximizes to 50MPa at 250°C and then a reduce to 25MPa at 350°C. These stress variations correlate well with thickness variations in film with temperature.