Passivation of III-V Semiconductor Surfaces
Authors Contreras, Yissel; Muscat, Anthony
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Download date 05/02/2021 18:28:15
Link to Item http://hdl.handle.net/10150/306095
Passivation of III-V Semiconductor Surfaces
Yissel Contreras and Anthony Muscat • Department of Chemical & Environmental Engineering, University of Arizona, Tucson, AZ • ydcontreras @email.arizona.edu
University of Arizona Student Showcase • November 8, 2013
Computer logic chips of the last generation are based on silicon, modified to
achieve maximum charge mobility to enable fast switching speeds at low
power. III-V semiconductors have charge mobilities that are much higher than
that of silicon making them suitable candidates for boosting the performance
of new electronic devices. However, III-V semiconductors oxidize rapidly in air
after oxide etching and the poor quality of the resulting oxide limits device
performance. Our goal is to design a liquid-phase process flow to etch the
oxide and passivate the surface of III-V semiconductors and to understand
the mechanism of layer formation.
Self-assembled monolayers of 1-eicosanethiol (ET) dissolved in ethanol, IPA,
chloroform, and toluene were deposited on clean InSb(100) surfaces. The
InSb passivated surfaces were characterized after 0 to 60 min of exposure to
air. Ellipsometry measurements showed a starting overlayer thickness (due
to ET, oxides, or both) of about 20 Å in chloroform and from 32 to 35 Å in
alcohols and toluene. Surface composition analysis of InSb with X-ray
photoelectron spectroscopy after passivation with 0.1 mM ET in ethanol
confirmed the presence of ET and showed that oxygen in the Auger region is
below detection limits up to 3 min after the passivation. Our results show
that a thiol layer on top of a non-oxidized or low-oxide semiconductor
surface slows oxygen diffusion in comparison to a surface with no thiol
present, making this a promising passivation method for III-V
semiconductors.
Highest room-temperature mobility of electrons (red) and holes (blue) in inversion layers and quantum wells as a function of the
semiconductor lattice constant (side length of a cubic unit cell of crystal)
del Alamo, J. a. (2011). Nanometre-scale electronics with III-V compound semiconductors. Nature, 479(7373), 317-23. doi:10.1038/nature10677
A self-assembled monolayer
ACKNOWLEDGEMENTS • Intel Corporation • National Council of Science and Technology (CONACYT, México) • Pablo Mancheno - Muscat Research Group
● Demonstrated adsorption of 1-eicosanethiol self-
assembled monolayers (SAMs) on the InSb(100)
surface.
● Polar solvents produced layers with a higher molecular
surface density and slower rates of oxidation.
● Demonstrated chemical passivation of InSb(100) for air
exposure up to 3 min.
Conclusions Future Work
● Study ET SAMs deposited on InSb(100) with AFM at various
times after thiol deposition to evaluate the surface
roughness.
● Perform the passivation process over longer periods of time
and characterize the deposited layers with ellipsometry, AFM,
XPS, FTIR, and contact angle measurements.
● Determine whether it is possible to desorb ET from the InSb
surface by temperature programmed desorption experiments.
Thickness of the overlayer on the InSb substrate
after passivation (measured with Ellipsometry), for
different solvents used in the thiol SAM formation
InSb(100)Oxide
InSb(100)Oxide
InSb(100)
InSb(100)
Methods
Solvent cleaning
2XHF etch
and H2O2 etch
HF etch HCl etch
Eicosanethiol SAM
deposition
Characterization
HF 1:100 v/v • H2O2 1M HF 1:100 v/v • HCl 1M
ET 0.1 mM20 min deposition
Solvents used
● Cyclohexane● Toluene● Chloroform● Ethanol● IPA
InSb(100)
Cl Cl Cl Cl Cl Cl l l l l l l
Ellipsometry • AFM • XPS
InSb(100)
AFM image of precleaned InSb(100)
AFM image of InSb(100) passivated with
eicosanethiol in ethanol
Height Image Amplitude error
X-ray Photoelectron Spectroscopy of ET passivated InSb substrates in various solvents. ET concentration used was 0.1 mM and deposition
time was 20 minutes in all cases but chloroform.
Acetone sonication
IPA
ETHANOL
TOLUENE
CHLOROFORM60 min deposition
Ra 2.74 nm
Ra 1.46 nm