In situ heating to improve adhesion for parylene-on-parylene deposition

A new technique of using “in-situ heating” to enhance adhesion for parylene-on-parylene deposition is reported in this paper. This method is compared with existing physical or chemical adhesion-enhancing methods and the results show clear advantages of this new technique. The physics is believed to be that the mobility of deposition-involved molecules (including the substrate parylene polymer chains and adsorbed monomers during deposition) is enhanced when deposition temperature rises, especially above the glass transition temperature of the substrate parylene. Each sample is patterned and then soaked in 0.9% saline at 90°C, and the undercut between two parylene layers due to the attack from saline during the soaking test could be observed. The undercut rate is measured to quantify the adhesion strength.