Evolution of residual stress in benzocyclobutene films with temperature

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 (3 MPa); while it maximizes to 50 MPa at 250 °C and then a reduce to 25 MPa at 350 °C. These stress variations correlate well with thickness variations in film with temperature.