Investigation of plasma parameters in dual antenna CF4/Ar/O2 inductively coupled plasma

In general, CF4/Ar/O2 mixture plasma have been wieldy used in semiconductor etching processes. It is required a dedicated and controllable etching technology in CF4/Ar/O2 etching system, but it is not easy to measure plasma parameters directly using a Langmuir probe because of depositing gas characteristics. 1 So, in this work, we measured plasma parameters for various radial and axial positions in inductively coupled plasma using floating probe (WISE probe) and optical emission spectroscopy. The plasma was generated in cylindrical chamber having 2-turn side antenna (13.56 MHz, 200 W) and 2-turn top antenna (2 MHz, 100 W) at 5 mTorr. Without top power, the profile of electron temperature and density show the two peaks near the side antenna. However, with top power, the profiles were abruptly changed into a bell-shape having a plateau around radial center. By increasing side-antenna power from 200 to 400 W with 50 W step, we found the plateau expansion to the chamber sides. On the other hand, we also measured axial distribution of plasma parameters. Both of electron temperature and density showed higher values at the point of side antenna position. However, with the top antenna, the axial profile was not changed but higher temperature and density were observed at whole axial positions. From the result, we found the dual-antenna ICP source can control the plasma uniformity by changing top-side antenna power ratio.2