Electron energy probability function measurement in a 2 MHz and 13.56 MHz dual-frequency capacitively coupled argon plasma

Abstract

The effect of low-frequency power and high-frequency power on the electron energy probability function (EEPF) and the physical and electrical characteristics of plasma are experimentally investigated in a dual-frequency capacitively coupled plasma. RF powers of 2 MHz (low-frequency) and 13.56 MHz (high-frequency) are simultaneously applied to an electrode. EEPFs and DC self-bias voltages (V DC) are measured as one of the two RF powers is increased while the other is fixed. When the 2 MHz power increases at a fixed 13.56 MHz power, the electron density decreases, and the electron temperature increases with the decrease in the population of low-energy (below 5 V) electrons in the EEPF. Note that the increase in the low-frequency power is accompanied by a large decrease in V DC, which is related to the ion energy. On the other hand, when 13.56 MHz power increases at a fixed 2 MHz power, the electron density and the electron temperature significantly increase with the increase in the population of high-energy (above 5 V) electrons in the EEPF, while V DC decreases slightly. Experimental results show that the increase in the low-frequency power enhances the ion energy, and the increase in the high-frequency power enhances electron heating and ionization efficiency.