User:Jeanmichel.sellier/Archimedes, the GNU package for semiconductor device simulations

= Archimedes, the GNU package for semiconductor device simulations =

Introduction
Archimedes is the GNU package for semiconductor device simulations that has been released for the first time on 2005 under GPL

license. It has been created by Jean Michel Sellier who is, since then, the leader of the project and the main developer. It is a Free software

and thus it can be copied, modified and redistributed under GPL license. This is the one of the big advantages of using Archimedes.

Archimedes belongs to the well-known family of TCAD software, i.e. tools utilized to assist the development of technologically relevant products.

In particular, this package assists engineers in designing and simulating submicron and mesoscopic semiconductor devices. According to the author,

in a future version Archimedes will also be able to simulate nanodevices, using the NEGF formalism. Today Archimedes is used in several big companies

for simulation and production purposes.

Archimedes is also useful for teaching purposes since everybody can access the sources, modify and test them. Today, it is used for teaching

purposes in several hundreds universities all around the world. Furthermore, a simplified version, developed for students, is available on nanoHUB.org.

The Ensemble Monte Carlo method is the method that Archimedes to simulate and predict the behaviour of a devices. Being the Monte Carlo

very stable and reliable, Archimedes can be used to know the characteritics of a device even before this last is built.

The Ethical Motivations, a New Paradigma in Science
Archimedes has been created after observing the situation of semiconductor simulations around the world.

One easily observes that the all codes developed for simulation are usually not free and/or proprietary codes.

That is a very bad situation, at least for accademic purposes, since it forces people to reinvent the wheel everytime

a piece of code is needed. This surely slows down the progress of Science (immagine you had to rediscover the Newtonian

laws every time you need them...).

The actual situation is that we have a huge amount of papers describing a lot of numerical methods for advanced simulations of

semiconductor devices, but nobody can access a single code on which to build new and even more advanced methods.

So, today, every university (and even every group in a university) has its own Monte Carlo simulator, its own NEGF simulator

and so on.. Would not it be better if we could avoid this incredibile duplication of efforts all around the world?

That is why Archimedes has been created...

Features
The main purpose of Archimedes is to simulate the transport of electrons and holes (light and heavy) in a semiconductor device.

Description of a device
A scripting language has been created and implemented with the aim to describe a semiconductor device in a fast and general manner.

The script is created by the user and Archimedes parses it to understand what has to be simulated and under which physical conditions.

For example, a Silicon diode script that can be parsed and interpreted by Archimedes is reported below:


 * 1) Silicon DIODE script


 * 1) To run it type:


 * 1) archimedes diode.input

MATERIAL SILICON

TRANSPORT ELECTRONS

FINALTIME 5.5e-12

TIMESTEP 0.0015e-12

XLENGTH 1.0e-6

YLENGTH 0.1e-6

XSPATIALSTEP 100

YSPATIALSTEP 25


 * 1) Definition of the doping concentration



DONORDENSITY 0. 0. 1.0e-6 0.1e-6 2.e21

DONORDENSITY 0. 0. 0.3e-6 0.1e-6 5.e23

DONORDENSITY 0.7e-6 0. 1.0e-6 0.1e-6 5.e23

ACCEPTORDENSITY 0. 0. 1.0e-6 0.1e-6 1.e20


 * 1) Definition of the various contacts



CONTACT LEFT 0.0 0.1e-6 OHMIC 0.0 5.e23

CONTACT RIGHT 0.0 0.1e-6 OHMIC 1.0 5.e23

CONTACT UP 0.0 1.0e-6 INSULATOR 0.0

CONTACT DOWN 0.0 1.0e-6 INSULATOR 0.0

NOQUANTUMEFFECTS

MAXIMINI


 * 1) SAVEEACHSTEP

LATTICETEMPERATURE 300.

STATISTICALWEIGHT 1500

MEDIA 500

OUTPUTFORMAT GNUPLOT


 * 1) end

Commands like MATERIAL and TRANSPORT specify the material and the model used in the device simulation.

For more info about the scripting language see the Archimedes manual.

Electron Transport Models
Archimedes implements several methods for the simulation of electron transport in semiconductor devices. Some of them are still work in progress,

somehow experimental, while others are completely implemented, tested and working models. The most reliable and most developed is the ensemble Monte Carlo method,

which has always been considered to be, both in the accademic and industry community, the most vigorous and trusted method for device simulation.

It has been shown to be reliable and predictive.

Monte Carlo Transport
For submicron devices, where semiclassic transport can be used succesfully, the Monte Carlo method is certainly the most reliable and trusted method.

The Monte Carlo method is based on the particle nature of electrons, when the quantum effects are so irrelevant that they can be neglected still getting

a good description of the physics involved in the device.

In this particular case, the main physical effects involved are:

All effects are taken into account in the current version of Archimedes.
 * Free flight
 * Phonons Scattering
 * Band effects

For details see this book

Wigner-Monte Carlo Transport
For mesoscopic devices, in which the transport can be still considered as semiclassic but where quantum effects start to be quite relevant, one has

to find a way to include quantum effects without loosing coherence with semiclassical transport. This is achieved using the so-called Wigner-Monte Carlo

method. An affinity, a mathematical artifact, is added to every particle in the simulation. This is still a work-in-progress in the actual version of Archimedes.<> For details see

NEGF Transport
For very small devices, where the quantum effects dominate the scene, the NEGF formalism has shown to be the most suitable one.

This is still a work-in-progress in Archimedes but it will be released as soon as possible.

For details, refer to this book

Materials
The materials taken into account in the simulations are:

i.e. the most important III-V materials for the semiconductor industry.
 * Silicon
 * Germanium
 * GaAs
 * GaP
 * GaSb
 * AlAs
 * AlP
 * AlSb
 * InAs
 * InP
 * InSb
 * Stechiometric combinations of the materials abbove

Examples
Some examples of results obtained by Archimedes are reported below. The two examples, a Silicon diode

and a Silicon MESFET, are well-known and well-understood devices that can be used as benchmarks to show

the reliability of Archimedes.

Simulation of a Silicon Diode
The script shown above has been run and the results are reported in this reference

Simulation of a Silicon MESFET
A MESFET has been successfully simulated by Archimedes. The results are reported in this reference

How to Support Archimedes
The development of Archimedes is a volunteer effort, and everyone can also contribute to its development.

For information about contributing to the Archimedes Projects and/or requests of enhancements and new features,

please contact the author at jeanmichel [dot] sellier [at] gmail [dot] com.

Future Developments
Future developments are certainly:

The future of Archimedes strongly depends on the semiconductor community. The more people uses it, the more the feedbacks.
 * Wigner-Monte Carlo methods
 * NEGF formalism

The more the feedbacks, the more new versions and so on..