Study On The Characteristics Of Dual-frequency Capacitively Coupled Ar/N₂ Plasma

With the developing of low temperature capacitively coupled plasma,they have widely used in industry,including preparation of Nano-film materials,semiconductor fabrication,surface cleaning and doping.To Dual-Frequency capacitively coupled plasma?DF-CCP?,the plasma density and ions energy could been controlled by high frequency source and low frequency source,so it is used to form large areas and uniformited discharge.In this paper,the discharged characteristics of Ar/N₂ driven by DF-CCP were studied.Dual frequency sources are 8MHz/100MHz and gas pressure is fixed at 0.03Torr,and the power of high frequency source changed from 5W to 40W and the percentage of argon changed from 70%to 100%.The spectrum of plasma was measured by optical emission spectrometer?OES?and the average electron temperature is achieved by a modified Boltzmann plot technique.The rotational and vibrational temperatures are acquired by comparing measured and calculated spectra of the second positive band?SPS?of nitrogen molecule.One-dimension particles-in-cell/Monte Carlo collision?PIC/MCC?is used to simulate electron density,ions density,the distribution of electric field and potential,and electron energy distribution function?EEDF?.The results show that the plasma density and vibrational temperature increased with the HF power increase and the average electron temperature and rotational temperature decreased with the HF power increase.The electron density and rotational temperature increased with the increase of argon content,and the electron temperature decreased with the increase of argon content,and the thickness of sheath layer does not change obviously with the increase of argon content.The electric properties of Ar/N₂ plasma are researched according to experiments.The voltage and current were measured by OCTIVE and Fast Fourier transform?FFT?were calculated.The results display that all voltage and current are non-sinusoidal and higher harmonics are present.The presence of higher harmonics in the discharge and an increase in their amplitudes is suggestive of a non-linear increase in the plasma density.Moreover,the equivalent resistance of plasma decreased with the increase of argon content and high frequency power,which is due to an increase of plasma density.