In SITU Spectroscopic Diagnostics of the Influence of Chamber Wall Polymer on Oxide Etch Rate

The drift of PECVD TEOS etch rate has been observed during MERIE oxide etch for damascene process. Etch rate typically fluctuates between 5300 Å/min. and 6000 Å/min. depending on chamber condition. Studies using fluorocarbon based chemistry show high TEOS etch rate when chamber wall is heavily coated with polymer deposition. Low etch rate appears when chamber has less deposition. Hysteresis behavior has been observed in TEOS etch rate and emission intensity trends ofF and CFx (x = 1 ∼ 3). From the correlation between etch rate and emission intensity, a model is proposed to explain the impact of chamber wall polymer deposition on TEOS etch rate. It clearly shows that F is directly responsible for the etch of TEOS. Comparing to F, CFx plasma chemistry has a closer link in chamber wall polymer formation, but less contribution in the etch of TEOS.