The Relationship Between Plasma Parameters And Chamber Wall Condition In An Inductively Coupled Plasma

To study the relationship between the chamber wall condition and the plasmaparameters in inductively coupled plasma (ICP), we changed the wall condition bychanging the wall size or by deposing/cleaning polymer film on the wall. Langmuirprobe is used to measure electron temperature, electron number density, plasmapotential and electron energy probability function (EEPF). Optical emissionspectrum is measured to determine the electron temperature and the relativeconcentration of radical particles. Experimental laws for the relationship betweenthese plasma parameters and the chamber wall condition are summarized. A study onthe effect of inert gas mixing on the electron energy probability function (EEPF) isalso included in this work. The main results are as follows.1. The influence of chamber size and polymer film coating on the wall to theplasma parameters. The influence of chamber size to electron temperature, plasmapotential and electron number density is summarized in Ar/N₂ and He/N₂ plasma at10mTorr, 400W. In film deposition (CH₄/Ar and C_H4/N₂ discharges) and cleaning(O₂/Ar and O₂/N₂ discharges) processes at 10mTorr and 200W, the experimentallaws for the variation of radical particle emission and electron temperature versusdischarge time are given.2. The periodical variation of plasma emission in the CH₄/N₂ discharge. Thecombining effect of light reflection and interference on the film-coated chamber wall,which is enhanced by the multiple reflections, causes the periodical variation ofemission detected by the spectrometer. Using a simple model, satisfactory agreementbetween the model and the experimental data was achieved. The facts that thepolymer film has a stronger absorption coefficient and the stainless steel surface hasa lower reflection rate for light of short wavelength are found out. The disturbanceeffect of the wall reflection on the calculation of electron temperature using line ratiotechnique is found. It is possible for us to measure the timely film thickness in thefilm deposition process with the help of this simple model.3. The sprout phenomena in low pressure plasma. The plasma sprouted out fromthe opening of a small chamber we putted in the diffusion region to make aconfinement, we call this sprouting part as jet. Its emission spectrum has largedifference from that of the bulk plasma. It has the effect of increasing electrontemperature. Its formation is considered to be the result of a radial electric fielddirected from the center to the wall.4. The tuning effect of mixing inert gas on electron temperature and EEPF. Fourkinds of gas mixture (Ar/N2, He/N2, Ne/N2 and Xe/N2) discharges are studied. Whenthe discharge gas changes from pure N2 to pure inert gas, the EEPF changes from asingle Maxwellian to a two Maxwellian structure in the Ar/N2 and Xe/N2 discharges,while the EEPF remain as a single Maxwellian structure with a smaller slope in theHe/N2 and Ne/N2 discharges. The distribution electron temperature of high energyelectrons has the same trend as the electron temperature calculated from spectrumand Global Model, while the distribution electron temperature of low energyelectrons has the same trend as that measured by a Langmuir probe. Detaileddiscussion is given to explain these facts.