A method and system for improved delivery of a solid precursor. A chemically inert coating is provided on system components in a precursor delivery line to reduce decomposition of a relatively unstable precursor vapor in the precursor delivery line, thereby allowing increased delivery of the precursor vapor to a processing zone for depositing a layer on a substrate. The solid precursor can, for example, be a ruthenium carbonyl or a rhenium carbonyl. The inert coating can, for example, be a CxFy-containing polymer, such as polytetrafluoroethylene or ethylene-chlorotrifluoroethylene. Other benefits of using an inert coating include easy periodic cleaning of deposits from the precursor delivery line.