Hybrid Simulation Of Electron Kinetic Properties In Radio Frequency Capacitively Coupled Plasmas Sustained In Reactive SiH₄/Ar Discharges

Low temperature plasma material processing plays a critical role in semiconductor fabrication.Among the plasma sources used in microelectronic fabrication,radio frequency capacitively coupled plasma(CCP)source as one of the most important low temperature plasma sources has been widely used in etching and films deposition.Nowdays,the size and etching width of the wafers encounter a high challenge owing to the fast development of the microelectronic technology,and it might be optimized by improving the efficiency of the plasma sources.Therefore,it is urgently needed for us to have a good knowledge of the low temperature plasma sources.Investigation of electron kinetic properties plays a significant role in the generation of etching and deposition precursors in reactive gas discharges.In this thesis,by using a fluid/electron Monte Carlo hybrid model,electron kinetics as well as their impacts on plasma properties induced by excitation collisions,electric field reversal and pulse modulated method are studied in radio frequeny capacitively coupled SiH4/Ar discharges.In the first chapter,the applications and challenges of the low temperature plasma sources in microelectronic industry are introduced.In addition,thorough introductions of the researches in electron non-equilibrium properties,electric field reversal,and pulsed radio frequency plasmas are introduced.In the second chapter,the fluid/electron Monte Carlo hybrid model is presented,with the fluid module,electron Monte Carlo mdule,chemical module,and the coupling procedure of these modules described in detail.In the third chapter,by using the fluid/electron Monte Carlo hybrid model,the non-equilibrium electron energy probability functions in radio frequency capacitively coupled SiH4/Ar charges are investigated.It is found that the electron energy probability function in the center of the bulk behaves muti-Maxwellian distribution,while exhibits Maxwellian distribution near the sheath region.By tracing the electron impacted collisions in the electron Monte Carlo model,it is concluded that the non-equilibrium electron property is mainly induced by SiH4 excitations.In addition,this non-equilibrium property can be reinforced by increasing SiH4 gas ratio and pressure,while is hardly impacted by the voltage amplitude.In the fourth chapter,by using the fluid/electron Monte Carlo hybrid model,the electric field reversal in the radio frequency capacitively coupled SiH4/Ar discharges is systematicly investigated.As a result,weak reversed fields and heating are detected outside the collapsing sheath edge in 10%SiH4 contained mixtures.Moreover,the reversed electric fields are significantly reinforced as SiH4 ratio increases to 90%,which can induce evident electron heating and electron creation.In addition,as the pressure and voltage amplitude increase,the electric field reversal obviously increases.In the fifth chapter,by utilizing the hybrid model,the pulsed radio frequency capacitively coupled Ar and SiH4/Ar discharges are studied.It is found that in 5 kHz pulsed radio frequency capacitively Ar discharges,as the pressure is fixed at 100 mTorr,the electron density increases gradually to a stable value during the power-on time.During this period,the electron density is hardly impacted by the duty cycle and pulse frequency.As the pressure increases to 300 mTorr,the electron density increases gradually to a peak value,which increases with the increasing duty cycle and the decreasing pulse frequency.As the power turns off,the electron density decreases to a relatively small value in all of these cases.In pulsed radio frequency SiH4/Ar plasmas,the tails of electron energy probability functions are enhanced at the initial power-on time,while shrink to stable distributions during the remaining power-on time.As the power turns off,tails of electron energy probability functions disappear,leaving bi-Maxwellian electron energy probability functions in the afterglow.In addition,densities of both positive and negative ions instantly increase in afterglow discharge,while the fluxes of positive ions on lower electrode decrease evidently.The density of SiH3 radical has little variation over the whole pulse period,while the density of SiH2 decreases somewhat in the afterglow.As a result,the deposition rate keeps almost constant,while the radical ratios can be controlled by the pulse modulated method.