Process development for dry etching polydimethylsiloxane for neural electrodes

In order to create high density electrode arrays, a reactive ion (dry) etching process was developed using sulphur hexafluoride (SF₆) and oxygen (O₂) plasma to pattern micro-structures in medical grade polydimethylsiloxane (PDMS). The surface topography and etch performance were analyzed by employing surface profilometry, scanning electron micrographs (SEM) and atomic force miscroscopy (AFM). The maximum etch rate was approximately 0.22 μm/min. The chemical modification of the PDMS structure in SF₆ and O₂ plasma was investigated through x-ray photoelectron spectroscopy (XPS). Micro-scale openings in PDMS were achieved using a dry etching method to allow charge injection at the electrode-tissue interface.