Designing chemical approaches for organic modification of silicon surfaces and thermal dry etching of cobalt thin films
Date
2017
Authors
Journal Title
Journal ISSN
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Publisher
University of Delaware
Abstract
Silicon and metal surfaces modified with organic molecule precursors are of
great importance to the semiconductor and electronics industries. However, it is
always a challenge to choose the most efficient precursors for forming a monolayer
with surfaces and to investigate the chemical changes on surfaces by controlling
critical conditions, such as surface temperature. In order to obtain a better
understanding of the reactions between organic molecules and surfaces, we combined
experimental results including infrared spectroscopy (IR), temperature programmed
desorption (TPD), X-ray photoelectron spectroscopy (XPS), and microscopic studies
together with density functional theory (DFT) studies. For silicon surface studies, we
focused on determining the reaction step that plays the key role in halide precursors
sticking probabilities and the influence of temperature on the formed monolayer. For
metal surface studies, we focused on the etching method to control the layer thickness
of thin metal films. ☐ During the process of achieving a halide-terminated Si (100) surface in ultrahigh vacuum (UHV), we compared the sticking probabilities of ethyl-chloride and
ethyl-iodide reacting with a clean Si (100) surface using TPD and DFT studies. It has
been demonstrated that the weakly bound precursor states of ethyl-halide on surfaces
determines the sticking probabilities during adsorption. At the same time, we applied
multivariate curve resolution (MCR), a mathematical method to simplify interpreting
the complex TPD spectra resulting from the low sticking probability of ethyl-chloride
adsorbing on silicon surfaces. ☐ In addition to halide-terminated Si (100) surfaces, amine-terminated Si (100)
surfaces are reactive and potential for further modification. We studied the adsorption
of triethylenediamine (TEDA) on a clean Si (100) surface as well as the adsorbents
while varying temperature. The experimental techniques including IR, TPD, XPS and
angular dependent near-edge X-Ray adsorption fine structure (NEXAFS) were
supplemented by DFT calculations. We concluded that the adsorption process can be
controlled by temperature: a datively bonded TEDA-Si-Si complex forms on the
surface at room temperature as well as at cryogenic temperature with low exposure;
heating above 400 K leads to C-N dissociation and ultimately the formation of surface
nitride and carbide species. ☐ A thermal dry etching process of cobalt thin films was investigated using 1, 1,
1, 5, 5, 5 -hexafluoro-2, 4-pentanedione (hfacH). The chemical species resulting from
thermal treatment were studied by IR, TPD, and XPS. The topography and
morphology of the surfaces were investigated by atomic force microscopy (AFM) and
scanning electron microscopy (SEM). The results indicated that the etching of cobalt
can occur Hhfac, but not with halogens.
Description
Keywords
Pure sciences, Chemical approaches, Cobalt thin films, Organic modification, Silicon surfaces, Thermal dry etching