Kinetic Simulations And Experimental Diagnosis Of Inductively Coupled Plasma Reactors

Inductively coupled plasma (ICP) sources are widely used for etching and deposition ofthin films in microelectronic manufacturing. Capability of obtaining uniform high-densityplasma at low gas pressure is the main merit of ICP over other approaches. In recent years,ICP has received intense investigations, for its strong non-local behavior and some peculiarphysical effects at low pressure, such as anomalous skin penetration and resonantwave-particle interaction. Understanding of these effects is the key issue on design andoptimization of ICP-based devices.In this thesis, a self-consistent kinetic model is developed to investigate the electronheating mechanism and anomalous skin effect of ICP discharge at low pressures. In chapter 2,a one-dimensional bounded plasma slab kinetic theory was firstly developed to study thecollisionless heating in the unmagnetized/magnetized inductively coupled Ar discharge. Theplasma slab here is stressed to be a simplification of a typical solenoidal ICP source. Influenceof dc magnetic field on the RF electric field penetration and negative power absorption wasalso discussed. A probable heating mechanism caused by Azbel-Kaner resonances issuggested for the magnetized ICP discharge.In chapter 3, a two-dimensional consistent kinetic model was developed for thesolenoidal ICP discharge to examine the effect of various factors on the electron energydistribution function. These factors include gas pressure, driving frequency, radius and lengthof the plasma reactor, amplitude of the RF coil current, and number of turns of RF coils.Numerical results show that the electron energy distribution functions are significantlymodified. The spatial profiles of the RF electric field and RF power density are alsocalculated under the same parameters. It is inferred that more uniform plasma can be obtainedwith increasing the number of turns of RF coils.In chapter 4, the RF electric field penetration and the power deposition into planar-typeinductively coupled plasmas in low-pressure discharges have been studied by means of aself-consistent model which consists of Maxwell equations and electron Boltzmann equationof electrons. The Maxwell equations are solved based on the expansion of the Fourier-Besselseries for determining the RF electric field. Numerical results show the influence of anon-Mawellian electron energy distribution on the RF electric field penetration and the powerdeposition for different coil currents. Moreover, the two-dimensional spatial profiles of RF electric field and power density are also shown for different numbers of RF coil turns. Theseresults are in good agreements with experimental measurements by Godyak et.al.In chapter 5, Langmuir Probe measurements with RF compensation are carried out in aplanar-type inductively coupled Ar, O₂, Ar/O₂ discharges. The effects of RF power and gaspressure on the plasma parameters, such as plasma electron density and electron temperature,were measured, which affirmed that high density, axial uniform plasma were generated in thisICP reactor at low pressures. The influence of O₂ flow rate on the electron energy distributionfunction in Ar/O₂ mixture discharge was also studied.