Abstract: A plasma-enhanced chemical vapor deposition system includes a number of process gas injection tubes and at least one dedicated clean gas injection tube. A plasma is used to periodically clean the interior surfaces of the deposition chamber. The cleaning is made more rapid and effective by introducing the clean gas through the dedicated clean gas injection tube. In this manner the clean gas can be introduced at a relatively high flow rate without detracting from the cleaning of the interior surfaces of the process gas injection tubes. As a separate aspect of this invention, a high-frequency signal is applied to both terminals of the coil during the cleaning process. This produces a plasma, mainly by capacitive coupling, which has a shape and uniformity that are well-suited to cleaning the surfaces of the deposition chamber.