Outline:

1
Computational Design of Si/SiO2 Interface for
Advanced and Future Electronics
Anatoli Korkin Nano Giga Solutions, Phoenix,
Arizona
Outline

• Retrospection and Forecast
• Atomic Scale Materials Design
• A few steps from atoms to devices
• Future Research
• Software Development

2
SiO2/Si Interface Why atomic scale insight is
needed
Conventional CMOS devices shrink to the nanoscale
dimensions
lt 10 nm
Source
Drain
lt 100 nm
New type of devices based on SiO2/Si interface
are emerging
Quantum dots
Nano wires
3
Materials chemistry at atomic scale
INPUTS
Material/Device Structure Data
Equipment Data
Process Data
tool geometries, flow rates
crystal type, grain boundary, interfaces, etc.
dopants, anneal temp
temp, pressure concentrations
MODELS
Reactor Models
Atomic Scale Deposition Models
Atomic Scale Film Device Models
Empirical reaction rate constants, Mechanisms
Ab initio reaction rate constants, Mechanisms
Film Interface structure
OUTPUTS
Deposition Rates, Film Uniformity Reactor
Process Design
Film Interface Structure Stability Process
Material Design
Electric Properties Reliability Device Design
4
An Integrated kMC-MD approach
DFT cluster periodic study reacting molecules
and barriers
Chemical kinetics calculations elementary
chemical reactions
Molecular dynamic simulation conformations
surface relaxation
Kinetic Monte Carlo simulation interface
formation film growth
A snapshot of an interface formation
5
Cluster Periodic DFT Study
Cluster models of hydroxylated oxidized Si(100)
surface
Cluster II
Cluster I
Periodic Slab
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SiCl4 Adsorption on OH Terminated Si(100) Surface
Adsorption complex Transition
state Product
?E (in kcal/mol) -12.1
1.7
-5.2
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Kinetics of Gas-Surface Reactions

• REACTION PATH PROFILES
• X ?Y/s gt Z ? W/s
• XMCl4 Y/s?SiOH Z ? HCl W/s ? SiOMCl3
  M Zr, Hf

8
A Scheme of the kMC-MD Program
.
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Model of Film Growth from Molecular Blocks

• Can be used to study
• Film structure and roughness vs substrate
  temperature
• Film structure and roughness vs energy of
  incident particles
• Film structure and roughness vs lattice misfit
• Stress relaxation in the film
• Non-equilibrium dynamical processes during
  deposition

• Describes film growth in
• Physical Vapor Deposition (PVD) process
• Molecular Beam Epitaxy (MBE)
• Ion assisted deposition (IAD) methods
• Chemical Vapor Deposition (CVD)
• Ion implantation

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Force Field Development
3.
Force Field potential
1.
2.
4.
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Model Implementation
Random position is selected over film surface. A
molecule at random orientation with random
velocity impinges on the surface
Layer connected with thermostat (velocity
rescaling)
Fixed layer to maintain structure
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Film Structure Dependence on the Substrate
Temperature Energy of Incident Particles
T 1500 K, E 3 eV
T 900 K, E 3 eV
T 1500 K, E 30 eV
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Initial models of SiO2/Si(100) interface
3D
2D
N.Tit M. Dharma-Wardana, JAP, 86 (1999) 1
Pasquarello et al., PRL, 74 (1995) 1024
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Relative energies of oxygen vacancies
4
3
2
1
O1 O2 O3 O4 2D 0.0 0.27 0.55 0.39 3D 0.0 - - 0.43
in eV
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E Centers OH defects
2D 0.26 3D 0.60
0.0 0.0
Bulk
Interface
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Novel interface models. I.
111
100
110
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Novel interface models. II.
(100)
(111)
(110)
(d)
(e)
(f)
Fig. 4
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I. Stress Energies at Si-SiO2 Interfaces
m-n/2 Si n/2SiO2 ? SimOn
?E (eV)
Novel interfaces
Dharma -Wardanas Extra layer of Si Less O at the
interface
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II. Stress Energies at Si-SiO2 Interfaces
Chemical (Hamann, PRB, 2000) Si(1)0.47
Si(2)0.51 Si(3)0.24
Mechanical Bond lengths and angles are not at
optimal
Polarization Coulomb interactions
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Elementary quantum dots Si-in-SiO2 and SiO2-in-Si
Si dot in SiO2
SiO2 dot in Si
O -0.32 (0.94) 2O 1.08 (1.45) 3O 2.64
(1.65) 4O 3.84 (1.88)
-O 1.84 (0.48) -2O 3.13 (0.99) -3O 4.94
(1.19) -4O 5.14 (0.96)
Total stress (chemical stress)
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1 nm Si wire in 2 nm SiO2 box Initial steps

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1 nm Si wire in 2 nm SiO2 box Generic view
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1 nm Si dot in 2 nm SiO2 box clever (?) guess
ß quartz 3 x 3 x 3 Si (100) 2 x 2 x 2 a b
c 21.48 Å a ß ? 90o Si243O401 Si -
42½ SiO2 - 201½
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1 nm Si dot in 2 nm SiO2 box
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Si/SiO2/Si Gate Stack Model
Total potential (eV)
Leakage current (A/cm2)
L. Fonseca et al.
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Model SiO2/Si/SiO2 channel
H-saturated Pb centers
L. Fonseca et al.
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Transport results for SiO2/Si/SiO2
L. Fonseca et al.
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KHIMERA Kinetics from Molecules to Reactor
I. Quantum chemistry
Reactant
Transition state
Product
Minimum energy path
II. Chemical Kinetics
III. Reactor Modeling
Individual reaction rates
Complex chemical kinetics
Chemistry in CVD reactor
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quantum chemistry
Import of QC Results
Viewing of the Molecular Structure
Initial Settings for Reaction Rates Calculation
Summary of QC Results
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Calculated Reaction Rates
Individual rate constants
Results of Thermochemical Calculations
Graphical Representation of Results
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Model, and process conditions
Reactor modeling
Results
Initial conditions and calculation details
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SAGEMD Atomic scaleaterials design
Pre-processor using GUI (with OpenGL based
graphic engine)
Solver (Fortran-90 modules)
Post-processor using GUI
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Structure Modification
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Property Analysis
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Summary
1. Designed novel SiO2-Si interfaces with (111)
and (110) surface termination comparable in the
quality with SiO2-Si (100) 2. Incorporation of
initial oxygen atom in Si demonstrates
thermo- dynamic stabilization effect.
Future plans
1. Comparative study of SiO2-Si and other
dielectric/semiconductor Interfaces for advanced
and future electronics SOI, novel devices,
etc. 2. Comparative study of SiO2-Si interfaces
in planar structures, wires, and quantum dots,
e.g. 1D- vs 2D- vs 3D-nanostructures.
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Acknowledgement
Co-authors University of Florida R. Barlett
SEMATECH G. Bersuker Tyndal National
Institute, Ireland J. Greer
Collaboration Brazil L. Fonseca Japan
K. Yamashita Russia A. Aleynikov, A.
Knizhnik