Optical Diagnostic Studies in Plasmas and Plasma Processing

Abstract

AbstractOptical diagnostic probes have greatly increased our understanding of low pressure discharges used in etching and deposition processes for microelectronics fabrication.Optical emission induced by energetic electron impact excitation provides a qualitative determination of concentrations of a number of important atoms and small radicals.Rare-gas actinometry, combined with high resolution line-shape measurements can convert emission data into quantitative relative number densities, and provide information on mechanism of excited state formation.Emission from products of etching reactions gives insights into mechanisms and serves as an end-point indicator for many commercial processes.Laser induced fluorescence is a sensitive probe which is most useful for small radicals.Quantitative, relative ground-state number densities, internal energy distributions, translational energies and electric fields can be determined by this technique.When optical emission or laser induced fluorescence measurements are performed with spatial resolution and in-phase with respect to the applied field, additional insights are obtained on the dynamics of the discharge processes.Finally, infrared and visible-ultraviolet absorption spectroscopy can be used to measure absolute number densities.This technique also can provide spatial and temporal resolution.This paper reviews and compares the various optical techniques used in plasma diagnostics with particular emphasis on studies of low pressure radio frequency discharges used in etching and deposition of thin films.