RADICAL CONTROL BY WALL HEATING OF A FLUOROCARBON ETCHING REACTOR

The entire vessel of a RF diode etching reactor was heated to control the radical composition of a CF4/H-2 plasma. Appearance mass spectrometry revealed that the CF3 and CF2 densities are 2 to 3 orders of magnitude higher in the heated reactor at 230 degrees C, compared with the conventional reactor at 30 degrees C. On the other hand, the F atom density monitored by an actinometry technique is almost unchanged. The temporal variation of the CF3 and CF2 densities induced by H-2 addition is relatively smaller in the heated environment. A few mechanisms for the anomalous increase of the CFx radical are discussed in view of the radical surface loss and the electron-impact radical production. As a consequence, wall heating is useful for controlling the etching processes by enhancing the carbon-containing radicals.