Diagnosis Of Capacitively Coupled O₂-containing Ar Plasma Driven By 27.12 MHz

Capacitive coupled discharge driven by high frequency is widely used in semiconductor industries.In this work,by using Langmuir probe and laser induced photodetachment techniques,we have mainly focused on investigation on the properties of the capacitively coupled O2-containing Ar plasma driven by radio frequency(RF)of 27.12 MHz.In the first part of this thesis,Langmuir probe technique was employed to measure the electrical parameters of capacitively coupled Ar plasma.The measurement results showed that a transition of the electron energy probability distribution function(EEPF)from bi-Maxwellian to single-maxwellian and finally to a Druyvesteyn distribution occurred as increasing RF input power or discharge pressure.This transition indicated the evolution of the heating mode in the Ar plasma as changing the discharge conditions.The axial electron density obtained by calculating the axial EEPF increased linearly along the axial direction.At low pressure,the electron density took on a tendency of decrease close to the power electrode due to the influence of the sheath.In the second part,by using combination of Langmuir probe and LIPD techniques,we have diagnosed the electrical properties of O2-containing Ar plasma driven by 27.12 MHz.Addition of 5%O2 gas into Ar plasma leaded to the clear deviation of the EEPF from the pure Ar plasma case.This deviation became more serious at high pressure due to the inelastic collisions of electrons with oxygen molecules.Additionally,different from the linear electron density along axial in Ar plasma,the addition of O2 not only lowered the electron density in the axial direction,but also smoothed the electron density distribution close to the powered electrode.LIPD measurement results showed that electronegativity in 5%O2-containing Ar plasma tended to be high as closing to the powered electrode,while to be a V-shaped distribution along the axis direction with increasing pressure.This behavior of negative ion distribution may be caused by the combined effects of recombination of negative and positive ions and the pseudo-y mode of negative ions with oxygen neutrals.On the other hand,we also measured the Ar plasma in different O2 condition.With the increase of O2 ratio,EEPF's low-energy peak decreased clearly and shifted to the high energy direction,which means low-energy electron depleted and electron density decreased significantly.Furthermore,the space potential and electron temperature under high percentage of O2 tended to be high.These phenomenon may be great related to dissociation reaction and attachment reaction in Ar+O2 plasma.