Suppression of harmonics and improvement of plasma uniformity by a parallel resonance in a capacitively coupled plasma

A method for suppressing the non-linearity of plasma and improving the plasma uniformity in a capacitively coupled plasma (CCP) is developed. Plasma contains harmonics due to the non-linear characteristics of the sheath. These high frequency harmonic components have bad influence on the plasma uniformity because the electromagnetic effects such as standing wave effect become severe at the high frequency. To improve the plasma uniformity, the CCP using a parallel inductor which is connected to the powered electrode is developed. By generating the parallel resonance between the plasma and a parallel inductor, the ratio of the fundamental frequency component in the total plasma current was greatly increased and the ratio of the higher harmonic components was significantly decreased. Under the parallel resonance condition, the ratio of the second and third harmonic components was decreased by about half and one third, respectively, and the voltage and current of the plasma increased significantly. As a result, not only the plasma density but also the plasma uniformity is improved.