Transcript Computational Design of Si/SiO Interface for Advanced and Future Electronics Outline:

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
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SiO2/Si Interface: Why atomic scale insight is needed
Conventional CMOS devices shrink to the nanoscale dimensions
< 10 nm
Source
Drain
< 100 nm
New type of devices based on SiO2/Si interface are emerging
Quantum dots
Nano wires
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Materials chemistry at atomic scale
INPUTS
Equipment Data
tool
geometries,
flow rates
MODELS
Empirical
reaction rate
constants,
Mechanisms
Reactor
Models
Material/Device
Process Data
Structure Data
dopants,
anneal temp
temp, pressure
concentrations
Atomic Scale
Ab initio
reaction rate
constants,
Mechanisms
Deposition
Models
crystal type,
grain boundary,
interfaces, etc.
Atomic Scale
Film &
Interface
structure
Film & Device
Models
OUTPUTS
Deposition Rates,
Film Uniformity:
Film & Interface
Electric Properties
Reactor & Process
Design
Structure & Stability:
& Reliability:
Process & Material Design
Device Design
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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
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Cluster & Periodic DFT Study
Cluster models of hydroxylated oxidized Si(100) surface
Periodic Slab
Cluster II
Cluster I
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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
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-5.2
Kinetics of Gas-Surface Reactions
•
•
REACTION PATH PROFILES
X Y/s ==> Z  W/s
X=MCl4; Y/s{Si}–OH; Z  HCl; W/s  {Si}–OMCl3; M = Zr, Hf
Urp
Urp
C+


C-
C-
uo,0
X + Y/s
uo
0
C/s
uo,-
uo,+
0
0
qr
X + Y/s
Z + W/s
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C+
uo
o,+
u0
0
C/s
qr
Z + W/s
A Scheme of the kMC-MD Program
Ewald sum and
optimal grid
generator
Molecular
mechanics
methods
Molecular
dynamics
solver
Summation rules,
QEq scheme,
neighbours search
algorithm Tersoff
correlation
Graphic view
.
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Potential
library
Kinetic MC
solver
Model of Film Growth from Molecular Blocks
Describes film growth in:
Can be used to study:
1.
Physical Vapor Deposition
(PVD) process
1.
Film structure and roughness vs
substrate temperature
2.
Molecular Beam Epitaxy
(MBE)
2.
Film structure and roughness vs
energy of incident particles
3.
Ion assisted deposition (IAD)
methods
3.
Film structure and roughness vs
lattice misfit
4.
Chemical Vapor Deposition
(CVD)
4.
Stress relaxation in the film
5.
Non-equilibrium dynamical
processes during deposition
5.
Ion implantation
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Force Field potential
E   Ei 
i
1
Vij

2 i j
Zr-O bond energy (eV)
Vij  f C rij aij f R rij   bij f A rij 
20
O
H
O
10
O
O
EtUHF
EsMP2
EtMP2
EsRHF
B
Z
r
H
H
H
0
0.1
H
r

Si
H
singlet
triplet
0.2
0.3
0.4
r (nm)
0.5
0.6
0.7
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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 = 900 K, E = 3 eV
T = 1500 K, E = 3 eV
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T = 1500 K, E = 30 eV
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
2D
3D
O1
0.0
0.0
O2
0.27
-
O3
0.55
-
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O4
0.39
0.43 in eV
E’ Centers + OH defects
O
e-
O
Si
Si
I
Si
Bulk
Si
Si
III
Si
2D: 0.26
3D: 0.60
Si
Si
O
O
Si
Si
Si
II
O
O
O
Si
Si
Si
Interface
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O
Si
0.0
0.0
Si
Novel interface models. I.
100
111
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110
Novel interface models. II.
(100)
(111)
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(110)
I. Stress Energies at Si-SiO2 Interfaces
m-n/2 {Si}
+ n/2{SiO2} → {SimOn}
Lattice
Novel interfaces
Dharma -Wardana’s
Extra layer of Si
Less O at the interface
ΔE (eV)
GGA
LDA
{Si50O40-111}
9.64
9.08
{Si66O40-111}
10.52
9.88
{Si60O52-110}
10.01
8.88
{Si52O44-100}
10.78
11.12
{Si68O44-100}
11.19
11.58
{Si52O36-100}
8.58
9.00
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II. Stress Energies at Si-SiO2 Interfaces
Chemical:
TOTAL
CHEM (∆)
{Si50O40-111}
9.64
5.68 (3.96)
Si(+3)=0.24
{Si66O40-111}
10.52
5.68 (4.84)
Mechanical:
{Si60O52-110}
10.01
5.68 (4.33)
{Si52O44-100}
10.78
6.80 (3.98)
{Si68O44-100}
11.19
6.80 (4.39)
{Si52O36-100}
8.58
5.68 (2.90)
(Hamann, PRB, 2000)
Lattice
Si(+1)=0.47
Si(+2)=0.51
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
Total stress
-O: 1.84 (0.48) -2O: 3.13 (0.99)
-3O: 4.94 (1.19) -4O: 5.14 (0.96) (chemical stress)
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+O: -0.32 (0.94) +2O: 1.08 (1.45)
+3O: 2.64 (1.65) +4O: 3.84 (1.88)
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
β – quartz: 3 x 3 x 3
Si (100): 2 x 2 x 2
a = b = c = 21.48 Å
α = β = γ = 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
Reactant
Transition state
Individual reaction rates
Product
Complex chemical kinetics
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Minimum energy path
Chemistry in CVD reactor
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
Results of
Thermochemical
Calculations
Graphical Representation
of Results
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Model, and process conditions
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 thermodynamic 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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Co-authors:
University of Florida: R. Barlett
SEMATECH: G.
Tyndal National Institute, Ireland:
Bersuker
J. Greer
Collaboration:
Brazil: L. Fonseca Japan: K. Yamashita
Russia:
A. Aleynikov, A. Knizhnik
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