Abstract: A process for etching a substrate 20 in a process chamber 25 having sidewalls 30 and a sacrificial collar 100, and for cleaning the sacrificial collar without eroding or otherwise damaging the sidewalls. The process comprises an etching stage in which a substrate 20 is placed in the process chamber 25, and the sacrificial collar 100 is maintained around the substrate to add or remove species from a process gas to affect a processing rate of the substrate periphery. The process further comprises a localized cleaning stage in which the substrate 20 is removed, a cleaning gas introduced into the process chamber 25, and a localized cleaning plasma sheath 95 is formed to clean process residues formed on the sacrificial collar 100 substantially without extending the localized cleaning plasma sheath 95 to the sidewalls 30 of the process chamber.