The generation of higher harmonics in capacitively coupled argon plasma driven by 8 MHz, 100 MHz and 8/100 MHz

Abstract

The generation of higher harmonics in capacitively coupled argon plasma (CCP) driven by 8 MHz (60 W), 100 MHz (10-40 W) and dual frequency 8/100 MHz (high frequency power of 10-40 W) are studied when the pressure is 30 mTorr. At dual frequency 8/100 MHz, the number of harmonics in the voltage and current measured on the discharge electrode is the largest, and the number of harmonics increases with the increase of high frequency (HF) power. The amplitude of the corresponding harmonics of dual frequency 8/100 MHz is between single 8 MHz (60 W) and single 100 MHz (10-40 W). The measured voltages on the discharge electrode are used to calculate the electron density, electron temperature, electric field, current density and electron heating of 8 MHz (60 W), 100 MHz (10-40 W) and 8/100 MHz (high frequency power of 10-40 W) at the pressure of 30 mTorr by Particle-in-cell/Monte Carlo collision (PIC/MCC) methods. The simulated results show that the harmonics amplitude of the electric field and current density in the bulk center reach the largest with the HF power increase in 8/100 MHz. The sheath thickness gradually narrows at different HF power with the electron density increase. At dual frequency (8/100 MHz), the electron density and electron temperature are higher than 8 MHz and lower than 100 MHz. The electron heating mainly occurs at the boundary between the sheath and plasma. The plasma series resonance (PSR) effect and dual frequency coupling effect can generate multiple harmonics in dual frequency CCP discharge. The expansion and collapse of sheath indicate that the electrons gain and lose energy respectively because of PSR.