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