Characterization of rf cylindrical magnetron plasmas and reactive ion etching of silicon/silicon dioxide: Its effect on radiation damage and contamination
Yeom, Geun Young
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https://hdl.handle.net/2142/19030
Description
Title
Characterization of rf cylindrical magnetron plasmas and reactive ion etching of silicon/silicon dioxide: Its effect on radiation damage and contamination
Author(s)
Yeom, Geun Young
Issue Date
1989
Doctoral Committee Chair(s)
Kushner, Mark J.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Electrical Engineering
Materials Science and Engineering
Language
eng
Abstract
Radio Frequency (rf) cylindrical magnetron glow discharges of Ar, He, and CF$\sb4$ driven at 1.8MHz and 13.56MHz have been characterized using electrostatic probes, optical emission spectroscopy and optical actinometry. Also the etch rates and etch profiles of Si/SiO$\sb2$ for 13.56MHz were studied for various conditions in CF$\sb4$/H$\sb2$ and CHF$\sb3$ plasmas as a function of magnetic field strength. The degree of radiation damage and contamination generated during the etching was also investigated. A variety of effects were observed as the magnetic field strength, applied perpendicular to the electric field to trap electrons, was varied from 0 to 250G. As the magnetic field strength increased, the plasmas became more resistive and the dc self-bias voltage at 1.8MHz was much higher than at 13.56MHz. The measured time-averaged ion densities for Ar plasmas varied as a function of radial position between the two electrodes, from 1 $\times$ 10$\sp9$ cm$\sp{-3}$ to 5 $\times$ 10$\sp9$ cm$\sp{-3}$ at OG. At 200G, this variation was 1 $\times$ 10$\sp{10}$ cm$\sp{-3}$ to 3 $\times$ 10$\sp{10}$ cm$\sp{-3}$. Furthermore, the position of the maximum in the ion densities shifted towards the powered electrode as the magnetic field strength increased. With CF$\sb4$/H$\sb2$ and CHF$\sb3$, the radical and ion densities increased almost linearly with increasing magnetic field strength and the self-bias voltages decreased exponentially from 1kV at OG to virtually no bias voltage at 250G while at constant power densities. The etch rates of Si and SiO$\sb2$ increased with increasing magnetic field strength until the threshold ion bombardment energy corresponding to a dc bias of about 50V was reached. Further increase of magnetic field strength decreased the etch rates. Also, near the highest etch rate conditions, the degree of contamination was minimum. Radiation damage monotonically decreased with increasing magnetic field strength, a consequence of the decrease in dc bias. Etch profiles changed from tapered to re-entrant profile with increasing magnetic field strength. Vertical etch profiles of Si and SiO$\sb2$ having 2$\mu$m depth and 200nm line features were obtained near the highest etch rate conditions (faster than 250 nm/min) with little or no radiation damage and minimum contamination.
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