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Marek Mierzwinski*, Dondee Navarro**, and Mitiko
Miura-Mattausch**
*Keysight Technologies **Hiroshima University
An Overview of the HiSIM SOI/SOTB Compact Models
MOS-AK 2017
2MOS-AK December 2017
Agenda
• Introduction
• Model overview
• Model theory
• Model applications
• CMC standard implementation
3MOS-AK December 2017
Silicon On Insulator technology
• SOI technology provides key advantages for high performance devices
• Reduced junction capacitances
• Improved subthreshold voltage swing
• Improved isolation
• Similar performance gains but less complex than FinFET
• Disadvantages
• Substrate cost
• Some process issues (stress)
4MOS-AK December 2017
Silicon On Insulator (SOI) MOSFET
SOI-MOSFETBulk-MOSFET
Buried oxide
5MOS-AK December 2017
• HiSIM2: Bulk MOSFET
• HiSIM-Varactor
• HiSIM_HV: HV-MOSFET, extension of HiSIM2
• HiSIM-IGBT: HiSIM2 + Bipolar + Diode
• HiSIM-SOI/SOTB
• HiSIM-TFT
• HiSIM-DG
H I R O S H I M A - U N I V E R S I T Y S TA R C I G F E T M O D E L
HiSIM
6MOS-AK December 2017
HiSIM-SOI Compact Model Key Features
• Considers all possible induced charges in the Poisson equation
• Derives accurate analytical solution as initial values
• Solves the Poisson equation iteratively
• Self heating accounted for
• History effect modeled
• Many other phenomenon
Standardized by CMC on 2012 July
7MOS-AK December 2017
Applicability of HiSIM-SOI compact model
• Partially Depleted (PD) as well as ultra-thin-body Fully Depleted (FD) SOI
• Voltage dependent Dynamic Depleted (DD) SOI
• Low voltage circuit application
• RF circuit simulation with noise prediction
8MOS-AK December 2017
HiSIM-SOI Model Implementation Steps
• Device physical characteristics such as thickness of the SOI layer, thickness of the buried oxide
layer, and impurity concentration in the bulk must be able to be extracted.
• 3 surface potentials have to be accurately calculated
• Charges must be computed such that charge conservation is not violated
• Short channel effects must be accounted for
9MOS-AK December 2017
Extracted physical values
• Certain model parameters must be
determined
• Typically these values would be
extracted via measurement under
proper conditions to make certain
values more sensitive
10MOS-AK December 2017
Model parameter extractions from VBS
accumulation inversion
inversion accumulation
BOX
BOX
11MOS-AK December 2017
Three surface potentials induced in SOI-MOSFET
• Conventional bulk MOSFETs need only
solve for the surface potential at the front
oxide layer (FOX)
• The SOI MOSFET must also solve for the
potential at each side of the buried oxide
(BOX)
12MOS-AK December 2017
• Provides self-consistent current and capacitance characteristics
Surface potential-based modeling
13MOS-AK December 2017
Potential and Charge Basic EquationsDerived from Poisson Equation and Gauss’s Law
14MOS-AK December 2017
Implicit Relations
15MOS-AK December 2017
Newton-Raphson technique
• Developed circa 1700!
F φ𝑛
φ𝑛φ𝑖
φ𝑖+1
φi+1 = φ𝑖 −𝐹(φ𝑖)
𝐹′(𝜑𝑖)
Make
guess
Test answer
Close
enough
to 0?
Compute new
guess using
tangent.
Converged
16MOS-AK December 2017
Equation to solve
𝜙𝑖+1-𝜙𝑖 = −𝐽−1 ∙ 𝑓
17MOS-AK December 2017
Verilog-A Implementation
18MOS-AK December 2017
Iterations to calculate surface potential
• Newton-Raphson’s algorithm converges very
quickly.
• Number of iterations steps needed to
calculated the surface potentials at source
and drain as function of Vgs shown.
19MOS-AK December 2017
SOI MOSFET operation mode
• The device geometry, physical parameters,
and operating temperature can all affect the
operation mode that the device is in
20MOS-AK December 2017
Many Possible Structure Types For SOI
resulting in
different potential distributions
causing
different bias dependencies
TSOI TBOX Condition
Device 1 150 110 PD
Device 2 50 110 DD
Device 3 50 50 DD
Device 4 25 110 FD
Lines = 2D-TCAD
Circles = HiSIM
21MOS-AK December 2017
TSOI TBOXCondition
Device 1 150 110 PD
Device 2 50 110 DD
Device 3 50 50 DD
Device 4 25 110 FD
Smooth Transition among Conditions
Gate bias varied
22MOS-AK December 2017
Floating-Body Effect in HiSIM-SOI
bulk-MOSFET SOI-MOSFET
impact ionization
hole storage
Holes generated by
Impact Ionization
accumulate in SOI
layer
23MOS-AK December 2017
0.0
0.5
1.0
1.5
2.0 0.0 0.1 0.16 0.05
pote
ntial [V
]
SOIT BOXT
depth [mm]
2D-device simulation
w/o impact ionization
with impact ionization
Influence of Stored Charge
• Stored holes cause potential
redistribution
24MOS-AK December 2017
4.0
6.0
0.0
2.0
1.50.0 0.5 1.0
I d[1
0-5
A]
Vds[V]
SOI-MOSFET
bulk-MOSFET
Floating-Body Effect in HiSIM-SOI
• Accumulated holes affect bias potential
and drain current
• This manifests itself as an increase in
drain current, or kink
• Also causes history effect since prior
biases have an influenceKink effect observed
in SOI-MOSFET I-V
25MOS-AK December 2017
Modeling of Stored Charge: Qh
• Qh is included in the Poisson equation.
• The floating-body effect is automatically
included.
Qh=f(Isub: measured with BT device)
26MOS-AK December 2017
symbol: 2D-Sim.
line: HiSIM-SOI
fs.SOI
fb.SOI
fs.bulk
SOI
BOX
bulk
fb.SOI reduction change from FD to PD
HiSIM-SOI Results
FOX
27MOS-AK December 2017
History Effect
• Transient
Characteristics of the
Floating-Body Effect
• Implemented into
HiSIM-SOI in similar
way as the NQS effect
Td
Td: Time constant of Qh storage
Td 1/Isub
28MOS-AK December 2017
History Effect Implementation
Calculate
Contribute
29MOS-AK December 2017
Silicon On Thin Buried oxide MOSFET
• The potential distribution must be considered from the surface to the bottom of the substrate
explicitly
• All 4 potential values must be solved simultaneously
FOX BOX
30MOS-AK December 2017
Model Concept SOTB
• Similar Model Framework as HiSIM-SOI
• Complete Surface-Potential-Based Model
• Physically Consistent Modeling Approach
• Scalability with Device-Structure Changes
• More than HiSIM-SOI
• Applicable for Thin TSOI with high impurity concentration of Nsub
• Extendable for DG-MOSFET (inclusion of inversion condition at the
back side of TSOI)
Tox
Nsub
TBOX
NSOI
TSOI
31MOS-AK December 2017
Ves=+0.6V Ves=0 Ves=-0.6V
Various potential distributions and resultsBack gate control of the front gate charge
32MOS-AK December 2017
Phenomena Considered in HiSIM-SOI
• floating-body effect
• history effect
• valence-band tunneling
• noise characteristics
• self-heating
• body contact
• NQS effect
• impact ionization
• gate tunneling currents
• GIDL currents
• non-uniform doping effects
• channel length modulation
• velocity saturation, including overshoot
• short-channel effects
• width scaling effects
• bulk charge effect
• universal mobility
• field-dependent mobility
• finite inversion layer thickness
• parasitic bipolar
• diode junction currents / capacitances
33MOS-AK December 2017
Summary
• Silicon-on-insulator (SOI)-MOSFETs provide next generation of mainstream integrated circuits with
a technology that reduces junction capacitances and improves subthreshold swing, critical for a
high-speed device operation.
• The HiSIM SOI and SOTB device models, developed at Hiroshima University
• are Compact Model Coalition standards
• give device modeling engineers the capability to model complex device behavior in all SOI structures and
bias conditions
• a physical model
• good convergence capabilities
• Verilog-A source code allows easy access to
• all the implementation details
• self-documented code
• reference values under any conditions