Ion energy distribution in a radiofrequency C4F8 discharge

The dependence of ion energy distribution (IED) of a planar radiofrequency driven inductively coupled plasma source on pressure and power is analyzed by using a plasma monitor. The transition from capacitive coupling (E mode) to inductive coupling (H mode) is observed between 100 and 200 W for a C4F 8 gas pressure in the range from 0.8 to 8 Pa. In the H mode, the concentrat ion of light ions is higher due to an increase in dissociation and ionizati on rate Of C4F8. In the E mode, the IED consists of a large peak (around 20 eV) with an appearing saddle structure (0.8 Pa), whereas at higher pressur e (8 Pa), the IED exhibits an important contribution near zero energy, indi cating a collisional sheath. In the H mode, in most cases, the IED consists of one peak which is narrower for higher mass.