Adhesion-enhancing surface treatments for parylene deposition

Parylene-C has been extensively used in biomedical devices as a conformal and biocompatible coating. It is also a good material for implantation. Unfortunately, serious delamination between parylene-C and other materials is often found even during standard MEMS processes such as lift-off and sacrificial photoresist releasing. Therefore, surface treatments before parylene deposition that can enhance the interface adhesion between the deposited parylene and the coated surface are highly desirable. Interestingly, the chemical structure of Parylene-C does suggest that parylene-C deposition on a clean hydrophobic surface favors a good interface adhesion. This work is then to study various surface treatments, especially on silicon and another parylene-C surfaces, by hexane, toluene, propylene carbonate (P.C.), and tetrafluoromethane (CF₄) plasma. Our hypothesis is then good surface cleaning can lead to interface adhesion. We report the results here using parameters such as peeling force, soaking undercut rate, and vertical attack bubble density (VABD) to quantify the effectiveness of these adhesion treatments.