DEFECTS AND DOPANTS IN SEMICONDUCTORS
AND OXIDES
A.
Formation, structure and properties
of native defects in semiconductors:
Self-interstitials and
vacancies are fundamental native defects in all crystalline materials. Ballistic processes, which occur during
high-energy ion implantation during semiconductor manufacturing, lead directly
to a local vacancy excess at a depth near half the projected ion range and a
silicon interstitial excess distribution at a depth close to the ion
range. It is well established that
single interstitials and single vacancies are highly mobile in Si, even at room
temperature, allowing the excess interstitials and vacancies to remain in bulk
Si in the form of clusters or complexes with injected dopants. There have been significant efforts to
understand the fundamental behavior of these native defects as a consequence of
their crucial role in defining ultrashallow pn junctions for ever smaller semiconductor device fabrication. Using first principles-based atomistic
modeling, we have examined the formation, structure and thermal stability of
defect clusters under various strain conditions, and how the presence of
cluster defects affects the mechanical, optical and thermal properties of host
materials.
¡×
S. Lee, R.J. Bondi, and
G.S. Hwang,
¡°Formation and Structure of Vacancy Defects in Silicon: Combined Metropolis
Monte Carlo, tight-binding molecular dynamics, and density functional theory
calculations¡± Phys.
Rev. B 80, 245209 (2009).
¡×
R.J. Bondi, S. Lee and
G.S. Hwang,
¡°Theoretical Characterization of Silicon Self-Interstitial Clusters in Uniform
Strain Fields,¡± Phys.
Rev. B 80, 125202 (2009).
¡×
R.J. Bondi, S. Lee and
G.S. Hwang,
¡°Prediction of the Formation of Stable Periodic Self-Interstitial Chains [(I4)m, m=1-4] in Si under Biaxial Strain,¡± Appl. Phys. Lett. 94, 264101 (2009).
¡×
S. Lee, R.J. Bondi and
G.S. Hwang,
¡°Integrated Atomistic Modeling of the Growth and Structure of Self-interstitial
Defects in Silicon,¡± Molecular Simulation 35, 867 (2009).
¡×
R.J. Bondi, S. Lee and
G.S. Hwang,
¡°Biaxial Strain Effects on the Structure and Stability of Self-Interstitial
Clusters in Silicon,¡± Phys. Rev. B 79, 104106 (2009).
¡×
S. Lee and G.S. Hwang, ¡°Theoretical Determination of Stable
Fourfold-Coordinated Vacancy Clusters in Si,¡± Phys. Rev. B 78, 125310 (2008).
¡×
S. Lee and G.S. Hwang, ¡°Growth and Shape Transition of Small
Silicon Self-Interstitial Clusters,¡± Phys. Rev. B 78, 045204 (2008).
¡×
S. Lee and G.S. Hwang, ¡°Structure and stability of small
compact self-interstitial clusters in crystalline silicon,¡± Phys. Rev. B
77, 085210 (2008).
B.
Defects and impurities in amorphous
silica:
This proposal aims to
develop a deeper understanding of the fundamental behavior and properties of point-like
defects and chemical impurities in amorphous silica materials.
¡×
C.-L. Kuo and G.S. Hwang, ¡°Structure and
Diffusion of Boron in Amorphous Silica: Role of Oxygen Vacancy Related
Defects,¡± Phys.
Rev. B 79, 165201 (2009).
¡×
C.-L. Kuo, S. Lee, and G.S. Hwang, ¡°Structure and
Dynamics of Silicon-Oxygen Pairs and Their Role in Silicon Self-diffusion in
Amorphous Silica,¡± J. Appl. Phys. 104, 054906 (2008).
¡×
C.-L. Kuo and G.S. Hwang, ¡°On the Origin of
Nitrogen-induced Retardation of Boron Diffusion in Amorphous Silica,¡± Appl. Phys. Lett. 92, 92112 (2008).
C.
Structure and diffusion of
defect-dopant complexes in semiconductors:
This
research aims to develop
predictive kinetic models for ultrashallow junction formation in strained
silicon (Si) channels with amorphous thermal silicon dioxide (a-SiO2) gates, needed for rational experimental designs for the 45-nm node
or beyond.
Using first principles-based atomistic modeling, this theoretical
program concentrates on developing a deeper understanding of the
structure and dynamics of defect-dopant complexes in strained Si as well as at
the interfaces of strained-Si with a-SiO2. Based
on these fundamental understanding and data, with experimental validation, we
will develop predictive kinetic models for the evolution of defect and dopant
profiles during post-implantation annealing. The kinetic models will further be fed
into implantation (UTMARLOWE/TOMCAT) and diffusion (DADOS, FLOOPS) simulators
to predict the evolution of defect profiles during dopant concentration and
electrical activation profiles during post-implantation annealing.
¡×
N. Kong, T.A. Kirichenko, G.S. Hwang, and S.K. Banerjee,
¡°Arsenic defect complexes at SiO2/Si interfaces: A density
functional theory study,¡± Phys. Rev. B 80, 205328 (2009).
¡×
N. Kong, T.A. Kirichenko, G.S. Hwang, and S.K. Banerjee,
¡°Interstitial-based Boron Diffusion Dynamics in Amorphous Silicon,¡± Appl. Phys. Lett. 93, 082109 (2008).
¡×
S. Harrison, T. Edgar, and G.S. Hwang,
¡°Prediction of B-Sii-F Complex Formation
and Its Role in B TED Suppression and Deactivation,¡° J. Appl. Phys.
101, 66102 (2007).
¡×
S. Harrison, T. Edgar, and G.S. Hwang,
¡°Prediction of Anomalous Fluorine-Silicon Interstitial Pair Diffusion in
Crystalline Silicon,¡° Phys. Rev. B-rapid communication 74,
121201 (2006).
¡×
S. Harrison, T. Edgar, and G.S. Hwang,
¡°Interstitial-Mediated Mechanisms of Arsenic and Phosphorus Diffusion in
Silicon,¡° Phys. Rev. B 74, 195202 (2006).
¡×
S. Harrison, T. Edgar, and G.S. Hwang#,
¡°Interstitial Mediated Arsenic Clustering in Ultrashallow Junction Formation,¡° Electrochem. Solid-State Lett.
9, G354 (2006).
¡×
S. Harrison, T. Edgar, and G. S. Hwang, ¡°Structure,
Stability, and Diffusion of Arsenic-Silicon Interstitial Pairs,¡± Appl. Phys. Lett. 87, 231905 (2005).
¡×
S. Harrison, T. Edgar, and G. S. Hwang, ¡°Structure and
Dynamics of the Diarsenic Complex in Crystalline
Silicon,¡± Phys.
Rev. B 72, 195414 (2005).
¡×
T.
Kirichenko, D. Yu,
¡×
S.
Harrison, T. Edgar, and G. S. Hwang, ¡°Interaction between interstitials and
arsenic-vacancy complexes in crystalline silicon,¡± Appl. Phys. Lett.,
85, 4935 (2004).
¡×
T.
Kirichenko, S. Banerjee, and G. S. Hwang, ¡°Surface Chemistry Effects on Vacancy
and Interstitial Annihilation on Si(001),¡± Phys. Status Solidi B 241, 2303 (2004).