Multilayer ALD ceramic films for enhancement of parylene barrier properties in compliant neural probes with bonded chips

Abstract

The insulation capabilities of parylene-C thin films in phosphate buffered saline (PBS) are improved through their combination with ALD nanolaminate Al2O3 and TiO2 films. Insulation structures sealed with this ceramic exhibit a 5X lower failure rate compared to those sealed with parylene alone. The insulation of parylene-C probes including 50 µm-thick Si chips bonded using anisotropic conductive film (ACF) is also investigated. The insulation is less effective with the bonded chip present, but samples maintain an impedance above 1 GΩ at 0.1 Hz for over 5 weeks. Addition of nanolaminate results in a lower, but more stable impedance.