A real-time study of hydrogenated amorphous silicon, microcrystalline silicon, and amorphous silicon carbide growth by optically enhanced infrared reflectance spectroscopy
Katiyar, Monica
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https://hdl.handle.net/2142/21704
Description
Title
A real-time study of hydrogenated amorphous silicon, microcrystalline silicon, and amorphous silicon carbide growth by optically enhanced infrared reflectance spectroscopy
Author(s)
Katiyar, Monica
Issue Date
1994
Doctoral Committee Chair(s)
Abelson, John R.
Department of Study
Materials Science and Engineering
Discipline
Materials Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
A new, optically enhanced reflection infrared spectroscopy technique is presented to study thin film growth in real time. Here, real time means under actual processing conditions, with a short data acquisition time compared to film changes or growth rates. This technique has industrial application in monitoring and controlling processes which involve a large or complex parameter space. These include interface control and the fundamentals of crystal growth, plasma deposition, and etching. These applications are illustrated in the thesis by studying the deposition of hydrogenated amorphous silicon (a-Si:H), microcrystalline silicon ($\mu$c-Si:H), and hydrogenated amorphous silicon carbide $\rm (a-Si\sb{1-x}C\sb{x}$:H) thin films by reactive magnetron sputtering. Complimentary information about the film microstructure is obtained from real time spectroscopic ellipsometry measurements.
For a-Si:H growth, we present the first detailed and quantitative set of experimental data on hydrogen incorporation and release processes. The absorption due to the stretching modes of Si-H bonds (1800-2300 cm$\sp{-1}$) is used to quantify the increase or loss of H during film growth. A narrow component at $\sim$2100 cm$\sp{-1}$ corresponding to all SiH$\sb{\rm X}$ bonds on the physical surface is identified for the first time; the line width of this mode is used to distinguish signals from the bulk and the surface. Various combinations of growth flux (isotope labelling, hydrogen partial pressure between 0.1 and 2.0 mTorr) and substrate material (on SiO$\sb2$, a-Si, or a-Si:D) at substrate temperatures between 120 to 350$\sp\circ$C are used to quantify surface hydrogen coverage, hydrogen implantation, and H removal from surface and sub-surface.
We analyze the growth of $\mu$c-Si:H on SiO$\sb2$ substrate; no evidence of etching during $\mu$c-Si deposition is found. We also study the phase transformation of amorphous to microcrystalline silicon when an a-Si film is exposed to a pure H$\sb2$ plasma. The a-Si is first heavily hydrogenated and then transforms to $\mu$c-Si with a concomitant decrease in H content.
During a-Si$\rm\sb{1-x}$C$\rm\sb{x}$:H growth, a transition layer rich in hydrogen and carbon is observed between the film and the substrate; steady state growth is not achieved until $>$250 on A SiO$\sb2$, and $\sim$70 A on a-Si:H substrates.
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