The Properties Of Dual-frequency Capacitively Coupled Nitrogen And Oxygen Gas Plasma

Dual-Frequence Capacitively Coupled Plasmas?DF-CCPs?can independently control the ion flux and energy bombarded to the substrate surface,and slow the contradiction between etching rate and device damage during the plasma candle.Thereby,the technology is widely used in the fields of semiconductor chip etching and plasma cleaning.In this thesis,the nitrogen/oxygen plasma was prepared by the DF–CCP device,where the high-frequency frequency is 94.92 MHz and the low-frequency frequency is13.56 MHz.The electron excitation temperature,molecular vibration temperature?T_v?and rotation temperature?T_r?changed with high frequency or low power and gas pressure in nitrogen plasma are discussed.Moreover,the electron excitation temperature,electron density changed with high or low frequency power and gas pressure in oxygen plasma are discussed.In the first part of the thesis,the changes of the electron excitation temperature,vibration temperature of the nitrogenand rotation temperature in nitrogen discharge plasma with high-frequency power?HF power?,low-frequency power?LF power?gas pressure and other physical parameters were studied.The spectrum of NII?391.4 nm?and NIII?394.3 nm?were selected to diagnose the electron temperature under different conditions using the double-line intensity method.And,the emission spectrometry was used to calculate the vibration temperature?T_v?and rotation temperature?T_r?of the nitrogen plasma.For the second positive band system?C³?u-B₃?_g?varied from 372 nm to 382 nm,the emission spectra under different discharge conditions were fitted by Matlab program.In order to verify the correctness of the calculation results,the same results were obtained by fitting for 388 nm-400 nm.The results show that the intensity of the nitrogen spectrum increases with the increment of low-frequency power and high-frequency power,and decreases with the increment of gas pressure.When the low-frequency power was constant,the vibration temperature?T_v?decrease significantly and the rotation temperature?T_r?almost unchanged as the high-frequency power increases.When the low-frequency power is 30 W,the electronic excitation temperature decreases with the increase of the high-frequency power.But the electronic excitation temperature increases with the increase of high-frequency powerwhen the low-frequency power is 60 W.When the fixed low-frequency power is 30 W or 60 W,the vibration temperature T_v is significantly reduced and the rotation temperature T_r does not change much as the low-frequency power increases.When both high-frequency power and low-frequency power are 30 W,the electronic excitation temperature decreases with the increase of low-frequency power,the vibration temperature T_v increases first and then decreases and rotation temperature T_r does not change much with the increase of gas pressure.The electron excitation temperature decreases with increasing the gas pressure.In the second part of the thesis,the changes of the electron excitation temperature,electron density with the high-frequency power?HF power?and low-frequency power?LF power?gas pressure in the nitrogen discharge plasma were studied.The spectrum of OI?777.4 nm and 844.7 nm?were selected to diagnose the electron temperature under different conditions using the double line intensity method.And the electron density under different conditions was diagnosed using the absolute intensity method of continuous spectrum.The results show that the intensity of the oxygen spectrum increases with the increase of low-frequency power and high-frequency power and decreases with the increase of gas pressure.The electronic temperature shows an increment with the increase of high-frequency power,low-frequency power,and discharge pressure.The electron density decreases with the increase of high-frequency power,low-frequency power and discharge pressure.A combination of experiments and numerical simulation method were used in this thesis to systematically study the discharge characteristics of the plasma while different experimental parameters have changed.The thesis have made basic research for the next step of popularization and application,and furthermore,provided the theoretical support.