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FastBlaze

Ultra-Fast MESFET and HEMT Device Simulator

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FASTBlaze Ultra-Fast MESFET and HEMT Device Simulator

Introduction to MERCURY TCAD Framework

The MERCURY framework is an application-specific TCAD toolset designed for FET simulation

Three Main Foundations of MERCURYFast Simulations (typically less than 1 minute)Accurate Physical Models

Accessible to all engineers

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MERCURY Modules

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Inputparser

Comprehensive

material and transportparameter database

Mocasim

C-Interpreter

Core Simulation FastBlaze

HarmonicBalance

FastNoise Post Processing

FastMixedMode

Automated meshgenerator

Automatic solutionsection

Wide selection ofphysical models

DC IV extraction Small-Signal RF

extraction

impedance-field

calculationcoupled with localnoise servicecalculation

Multi-frequency

large signal RFsimulator

Circuit embedded

device simulation(large signal)

Two port extraction Equivalent circuit

extraction Noise parameterextraction

FastGiga

Lattice heatflow equation

Future

Future

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FastBlaze Applications (cont.)

Analyses possible:

ID-VDS for various VGSID-VGS for various VDSTransconductancePunchthrough

Gate capacitanceTime domain waveformsRF two-port parameter extraction (eg. s-parameters)RF parameters as function of frequency and bias

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How Fast is FastBlaze?

All timings on a Sun ULTRA10 workstation

All simulations were on a 0.5 um gate length recessed MESFET or pHEMT. The DC Id-Vd simulations weretaken over the range -2.0V

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MERCURY Method

Two phases to MERCURY solution:

Charge control simulation vertically under the gate, recess and capregions

Transport simulation across the channel solving Poisson, currentcontinuity, and energy balance equations

REFERENCESR. Drury & C.M. Snowden, "A quasi-two-dimensional HEMT model for microwave CAD applications", IEEE

Transactions on Electron Devices, Vol. ED-42, No. 6, pp.1026-1032, 1995

C.M. Snowden & R.R. Pantoja, "GaAs MESFET Physical Models for Process-Orientated Design", IEEETransactions on Electron Devices, Vol. ED-40, No. 7, pp.1401-1409, 1992

B. Carnez, A. Cappy, et al. "Noise Modeling in Submicrometer-Gate FET's", IEEE Transactions on Electron

Devices, Vol. ED-28, No.7, pp.784-789, 1981

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MERCURY Method

Solution method is fast because:

Charge control data stored and accessed directly as a lookup tableCurrent driven allowing integration method for carrier transportScales linearly with number of mesh points (N)

conventional schemes scale as NHighly efficient Newton solverAutomated IV bias control to minimize the number of solution points

required

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MERCURY Method

The consequences of the MERCURY approach are:

No need to tradeoff accuracy for speed. Rapid simulation allows useof the most sophisticated models

Meshing and bias stepping can be automatedInitial guesses and convergence control are taken care of inherentlyTwo-dimensional effects can be modeled such as punchthrough

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MERCURY Method: Experimentation

Parameters which can be varied without recalculating the chargecontrolgate lengthrecess or contact lithographytransport models and parametersextrinsic and intrinsic parasiticsgate workfunction

Parameters which can be varied but do require a new chargecontrol simulation

epitaxial layer materials or thicknessesdoping and trap densitiesrecess depthtrap occupation models

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FastBlaze Key Features

Two different classes of key features:

Advanced Physical Modelstransport tuned using Monte Carlo Simulation

User Oriented Featuresgrid generationbias steppingdirect simulation at any bias pointGUI for structure definition

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Automated Grid Generation

Adaptive mesh refinementuses field solution obtainedfrom very fine mesh (10A)adaptive step size control

based on Taylor expansion

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Mesh layout around the gate, automaticallygenerated within MERCURY. Typical meshsize at drain edge of gate 2.8 x 0.6nm.

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Automated Current Driven Bias Stepping

An automated DC-IV generator only samples biaspoints where needed. This provides a highly efficient

method to characterize DC performance.

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Integration with VWF Framework

Code developed in-house to commercial standards

Seamless integration with DeckBuild and TonyPlotGeneral purpose optimization with optimizerRSM and advanced DOE using the VWF Automation Tools

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Ultra-Fast MESFET and HEMT Device Simulator

A customized, FastBlaze specific, GUI enables rapid device definition.This includes the geometrical, model and solution description providing

a straightforward setup of the simulation.

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Advanced Physical Models

Boltzmann, Fermi and Quantum Statistics

Energy Balance always usedAdvanced transport models

Monte Carlo derived velocity and energy and momentum relaxationtimes

Gate conduction Models (thermionic emission)

Extrinsic parasitic simulation Interface and bulk traps Integrated with C-interpreter for user defined models

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Quantum Mechanical Simulation

Self-consistently solves the Schrodinger and Poisson equations inthe charge control

Solves arbitrary number of bound statesUses highly efficient eigen solver routine to maintain high speedShows wavefront broadening into adjacent layers

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Conduction Band Energy and Eigenspectrum

The conduction band edge for a delta-doped GaAs/AlGaAs/InGaAs/GaAspHEMT is illustrated together with the first eleven bound-state energy

levels calculated using the quantum models.

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Mocasim: Monte Carlo Simulator

A three valley ensemble Monte Carlo simulator

Calculates bulk electron transport parameters for arbitrary threevalley semiconductors

velocityenergy relaxation timemomentum relaxation time

Derives four-dimensional material parameter setapplied fielddoping densitymole fraction(s)lattice temperature

Used to derive transport parameters for device simulators such asFastBlaze

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Mocasim: Features

Includes nine scattering mechanisms:Polar optical phonon absorption and emissionAcoustic phonon scatteringEquivalent valley phonon absorption and emissionNon-equivalent valley phonon absorption and emissionImpurity scatteringSelf-scattering

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Monte Carlo Transport Parameters

The electron velocity for GaAs at 300K is shown as a function of net impurity densityand electric field. The Monte Carlo derived velocity is complemented by both energy

and momentum relaxation times for a wide range of material systems.

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Material Dependent Transport Parameters

Velocity-field characteristics for various III-V materials.

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Transport Parameter Comparison

Comparison of HEMT Id-Vd using correct multi-layer transport models.The AlGaAs transport parameters are derived from Mocasim.

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Hydrogenic Dopant Ionization Comparison

Effect of incomplete ionization on dopant and carrier densities. Bothtraps and dopant impurities have several occupation statistic models.

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InGaAs pHEMT Structure

2D representation of pHEMT structure created in the MERCURY GUI.Definition of epitaxy, doping and recess topography is menu-driven.

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Auto-Generated Mesh for pHEMT

Mesh is automatically generated and focused in the pHEMT channel.

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DC Characteristics

DC characteristics of the pHEMT displayedwith uniform bias steps for clarity.

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Small Signal S-Parameters for a pHEMT

The time-dependent simulation used for RF evaluation is able to transform directlyto a variety of two-port descriptions. Here the small signal s-parameters for a

pHEMT including external contact parasitics are displayed up to 25GHz.

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Recessed MESFET Conduction-Band Energy

Full 2D distributions are provided to allow direct visualization of thecalculated physical parameters. This figure shows the conduction band

edge for a recessed MESFET structure biased at VDS= 2V.

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Transconductance Variation with Recess Depth

FastBlaze allows rapid prototyping of device structures in terms oftopographical, epitaxial and doping variations. This figure illustrates

the effect of increasing recess depth on transconductance.

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Conclusion

FastBlaze provides:Ultra high speed simulation MESFETs and HEMTsUses accurate physical modelsMonte Carlo derived parameters for modeling carrier transportPowerful user interface integrated with VWF tools

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MERCURY Speed Comparison

MERCURY and ATLAS were both used to simulate a planar 0.5 gate length GaAsMESFET on a SUN ULTRA 10 workstation. The total simulation time for an Id-Vdfamily of curves at Vg=0, -0.5V and -1.0V .

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MERCURY ATLAS Comparison

ATLAS MERCURY

Mesh Points 1200 7550 (auto generated)

CPU Time (s) 1400 49

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