An Overview of the HiSIM SOI/SOTB Compact Models - MOS-AK€¦ · MOS-AK December 2017 33 Summary •Silicon-on-insulator (SOI)-MOSFETs provide next generation of mainstream integrated

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


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)


Silicon On Insulator (SOI) MOSFET

SOI-MOSFETBulk-MOSFET

Buried oxide


• 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


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


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


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


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


Model parameter extractions from VBS

accumulation inversion

inversion accumulation

BOX

BOX


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)


• Provides self-consistent current and capacitance characteristics

Surface potential-based modeling


Potential and Charge Basic EquationsDerived from Poisson Equation and Gauss’s Law


Implicit Relations


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


Equation to solve

𝜙𝑖+1-𝜙𝑖 = −𝐽−1 ∙ 𝑓


Verilog-A Implementation


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.


SOI MOSFET operation mode

• The device geometry, physical parameters,

and operating temperature can all affect the

operation mode that the device is in


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


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


Floating-Body Effect in HiSIM-SOI

bulk-MOSFET SOI-MOSFET

impact ionization

hole storage

Holes generated by

Impact Ionization

accumulate in SOI

layer


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


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


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)


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


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


History Effect Implementation

Calculate

Contribute


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


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


Ves=+0.6V Ves=0 Ves=-0.6V

Various potential distributions and resultsBack gate control of the front gate charge


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


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

Documents

An Overview of the HiSIM SOI/SOTB Compact Models - MOS-AK€¦ · MOS-AK December 2017 33 Summary •Silicon-on-insulator (SOI)-MOSFETs provide next generation of mainstream integrated