The present disclosure relates to a method of depositing a polymer layer, including: providing a substrate, having a sensor structure disposed on the substrate, to a substrate support within a hot wire chemical vapor deposition (HWCVD) chamber; providing a process gas comprising an initiator gas and a monomer gas and a carrier gas to the HWCVD chamber; heating a plurality of filaments disposed in the HWCVD chamber to a first temperature sufficient to activate the initiator gas without decomposing the monomer gas; and exposing the substrate to initiator radicals from the activated initiator gas and to the monomer gas to deposit a polymer layer atop the sensor structure.