Evaluation of octafluorocyclobutane as a chamber clean gas in a plasma-enhanced silicon dioxide chemical vapor deposition reactor

The evaluation of octafluorocyclobutane, (c-C4F8) as a new chemistry for plasma-enhanced chemical vapor deposition (PECVD) tool chamber cleaning is reported. Using a statistical design of experiments, the cleaning time and perfluorocompound emissions were measured in a Novellus Concept One 200, a widely used commercial PECVD tool. By mass spectrometry of the process exhaust, the effect of c-C4F8 flow rate, C4F8/O-2 feed-gas ratio, and pressure effects on cleaning time and perfluorocompound (PFC) emissions were determined. Experimental results and neural network analysis indicate that high oxygen levels (75-90 vol %) and pressure (4.0 Torr) achieve reductions in process clean times of 20%, reduce gas requirements and PFC emissions greater than 80% relative to the standard C2F6-based cleans. These process advantages, combined with the similar physical and discharge properties of c-C4F8 and C2F6, suggest good potential for this new chemistry as a drop-in gas replacement for current chamber cleaning applications. (C) 2003 The Electrochemical Society.