Parylene to silicon adhesion enhancement

Parylene-C has been used extensively in neural interface devices as a conformal, biocompatible coating; it has also recently become an integrated part of our parylene-cabled silicon probes. However, it is found over the years that its adhesion capability to silicon may be compromised after thermal treatments, cleaning, handling, bench testing and implantations. This paper explores extensively new techniques including annealing, melting, anchoring, and XeF₂ silicon surface roughening to enhance this adhesion. We report the first quantitative experimental data on the effectiveness of each through tearing, soaking, etching and ASTM peeling tests. The results show various improved adhesion means over the standard A-174 adhesion promotion, which can greatly benefit the use of parylene.