Analysis of Mechanism of Reactive Ion Etching by Real-time Spectroscopic Ellipsometry

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A multichannel spectroscopic ellipsometer equipped with a CCD detector has been developed and applied to the analysis of dry etching processes of thin Si_3N_4, SiO_2 and SiC films in O_2/CF_4 plasma. The results are summarized as follows :1.A multichannel ellipsometer consisting of a white light source (Xe lamp), a collimator, a rotating polarizer, a sample stage, a fixed analyzer, a spectrometer, a CCD detector, and a CCD controller has been originally designed and constructed.2.A series of calibration was carried out to eliminate systematic errors arising from optical systems of the ellipsometer. The performance of the ellipsometer was evaluated after the complete calibration ; the minimum acquisition time of one spectrum over the wavelength range of 470 to 1060nm is 100ms, and the standard deviation in ellipsometric parameters is less than 0.1 degrees.3.Thin films of Si^3N_4, SiO^2 and SiC have been deposited on Si and Pt substrates by ion beam sputtering. The deposition parameters suited to obtain stoichiometric compounds were determined through the analysis of chemical composition by XPS and AES.4.Etching processes of Si_3N_4, SiO_2 and SiC films in O^2/CF^4 plasma were examined by real-time spectroscopic ellipsometry. It was found that the rapid changes in the etching rate and microstructure of the films occur as etching proceeds.