Patterning PLA Packaging Films for Implantable Medical Devices

Microhot-embossing is a less complex and inexpensive alternative over standard photolithography for patterning poly(lactic acid) (PLA) films. However, direct patterning of discrete or through-thickness microstructures by conventional microhot-embossing is not possible due to embossing-caused residual film. Use of complex modifications in the embossing process can further prohibit its integration with other standard semiconductor fabrication processes. Plasma-based reactive ion etching (RIE) of embossing-caused PLA residual film can be a viable option potentially allowing integration of the conventional hot-embossing process with standard semiconductor fabrication processes. RIE etch-rates of PLA packaging films, hot-embossed with parylene-based thin-film cochlear implant-shaped stiffener structures, were characterized for oxygen $(O2)$⁠, nitrogen $(N2)$⁠, and argon (Ar) plasmas under two different process conditions. The etch-rates of PLA films for $O2$⁠, $N2$⁠, and Ar plasmas were 0.29–0.72 $μm$/min, 0.09–0.14 $μm$/min, and 0.11–0.15 $μm$/min, respectively. Complete removal of embossing-caused residual film has been demonstrated utilizing the etching results for $O2$ plasma. Also, the effect of RIE etching on resultant PLA film surface roughness has been quantified for the three plasmas.