Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > A step towards germanium nanoelectronics

The figure shows schematically the application of germanium in a CMOS (complementary metal oxide semiconductor) circuit. Note that germanium is only used in the regions of source (S), drain (D) and channel (C). Source and drain contain high concentration of foreign atoms (dopants) which provide the excess of free electrons (n+ regions) or holes (p+ regions).
The figure shows schematically the application of germanium in a CMOS (complementary metal oxide semiconductor) circuit. Note that germanium is only used in the regions of source (S), drain (D) and channel (C). Source and drain contain high concentration of foreign atoms (dopants) which provide the excess of free electrons (n+ regions) or holes (p+ regions).

Abstract:
The use of germanium instead of silicon as basic material of transistors would enable faster chips containing smaller transistors.

A step towards germanium nanoelectronics

Dresden | Posted on February 17th, 2010

However, a number of problems still have to be solved. Transistors are produced using foreign atoms that are implanted into the semiconductor material so that it becomes partly conducting. As this production step damages the material, it has to be repaired by subsequent annealing. So far it has not been possible to produce large-scale integrated transistors of a specific type (NMOS) using germanium. The reason: phosphorus atoms are strongly redistributed within the material during annealing. Two novel techniques, which were applied by scientists of the research center Forschungszentrum Dresden-Rossendorf (FZD) and international colleagues, overcome this dilemma. The results were published in Applied Physics Letters and Physical Review Letters.

Higher switching speeds than in silicon could be achieved using germanium and some other semiconductors. Germanium is particularly attractive since it could be easily integrated into existing technological processes. Germanium was the basic material of first-generation transistors before it was replaced by silicon at the end of the 1960s. This was due to the excellent electronic properties of the interface between the semiconductor silicon and its insulating and passivating oxide. However, this advantage cannot be utilized if transistor dimensions are further reduced since the oxide must then be replaced by so-called high-k dielectrics. This again stimulates science and industry to search for the most suitable basic material.

By inserting foreign atoms the conductivity of semiconductors can be varied in a purposeful way. One possibility is ion implantation (ions are charged atoms) with subsequent heat treatment, which is called annealing. Annealing of the germanium crystal is necessary as the material is heavily damaged during implantation, and leads to the requested electronic properties. While these methods allow for the manufacturing of p-channel transistors (PMOS) according to future technology needs (22 nanometer technology node), it was not possible to produce corresponding n-channel transistors (NMOS) using germanium. This is due to the strong spatial redistribution (diffusion) of the phosphorus atoms which have to be used in manufacturing the n+ regions.

Physicists from the FZD applied a special annealing method that enables repairing the germanium crystal and yields good electrical properties without the diffusion of phosphorus atoms. The germanium samples were heated by short light pulses of only a few milliseconds. This period is sufficient in order to restore the crystal quality and to achieve electrical activation of phosphorus, but it is too short for the spatial redistribution of the phosphorus atoms. The light pulses were generated by the flash lamp equipment which was developed at the research center FZD. Analysis of the electrical and structural properties of the thin phosphorus-doped layers in germanium was performed in close collaboration with colleagues from the Belgian microelectronics center IMEC in Leuven and from the Fraunhofer-Center for Nanoelectronic Technologies (CNT) in Dresden.

An alternative method to suppress phosphorus diffusion in germanium has been investigated by an international team consisting of researchers from Germany, Denmark and the USA, amongst them physicists from FZD. After ion implantation of phosphorus into germanium the sample was heated to a given temperature and then irradiated by protons. It could be demonstrated that this treatment leads to the reduction of phosphorus diffusion, too. The results of these experiments are explained by the influence of certain lattice defects (self-interstitials) that annihilate those lattice defects (vacancies) which are responsible for the mobility of the phosphorus atoms.

Thus, FZD physicists and their colleagues demonstrated that in principle it is possible to fabricate germanium-based n-channel transistors (NMOS) with dimensions corresponding to the most advanced technological requirements.

(Authors: Dr. Matthias Posselt / Dr. Christine Bohnet)

Publications:

C. Wündisch, M. Posselt, B. Schmidt, V. Heera, T. Schumann, A. Mücklich, R. Grötzschel, W. Skorupa, T. Clarysse, E. Simoen, H. Hortenbach, "Millisecond flash lamp annealing of shallow implanted layers in Ge", in: Applied Physics Letters. 95 (2009), 252107. DOI: 10.1063/1.3276770.

H. Bracht, S. Schneider, J. N. Klug, C. Y. Liao, J. Lundsgaard Hansen, E. E. Haller, A. Nylandsted Larsen, D. Bougeard, M. Posselt, C. Wündisch, "Interstitial-Mediated Diffusion in Germanium under Proton Irradiation", in: Physical Review Letters 103 (2009), 255501, DOI: 10.1103/PhysRevLett.103.255501.

####

About Forschungszentrum Dresden Rossendorf
The Forschungszentrum Dresden-Rossendorf, now a member of the Leibniz Association, will become new member of the Helmholtz Association as of January 2011. It is engaged in basic and application-oriented research.

For more information, please click here

Contacts:
Dr. Matthias Posselt / Clemens Wündisch
Institute of Ion Beam Physics and Materials Research
Forschungszentrum Dresden-Rossendorf
Phone: ++49 351 260 - 3279 / - 3032

Contact to the media:
Dr. Christine Bohnet
Public relations
Bautzner Landstr. 400, 01328 Dresden
Phone: ++49 351 260 - 2450
++49 160 969 288 56
Fax: ++49 351 260 - 2700

Copyright © Forschungszentrum Dresden Rossendorf

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Carbon nanoballs can greatly contribute to sustainable energy supply January 27th, 2015

The laser pulse that gets shorter all by itself: Ultrashort laser pulses have become an indispensable tool for atomic and molecular research; A new technology makes creating short infrared pulses easy and cheap January 27th, 2015

New pathway to valleytronics January 27th, 2015

Stomach acid-powered micromotors get their first test in a living animal January 27th, 2015

Possible Futures

GS7 Graphene Sensor maybe Solution in Fight Against Cancer January 25th, 2015

Nanotechnology in Energy Applications Market Research Report 2014-2018: Radiant Insights, Inc January 15th, 2015

'Mind the gap' between atomically thin materials December 23rd, 2014

A novel method for identifying the body’s ‘noisiest’ networks November 19th, 2014

Chip Technology

Researchers Make Magnetic Graphene: UC Riverside research could lead to new multi-functional electronic devices January 27th, 2015

Nanometrics to Present at the Stifel 2015 Technology, Internet and Media Conference January 27th, 2015

New pathway to valleytronics January 27th, 2015

Entanglement on a chip: Breakthrough promises secure communications and faster computers January 27th, 2015

Nanoelectronics

Electronic circuits with reconfigurable pathways closer to reality January 26th, 2015

Rice-sized laser, powered one electron at a time, bodes well for quantum computing January 15th, 2015

Rapid journey through a crystal lattice: Researchers measure how fast electrons move through single atomic layers January 14th, 2015

A new step towards using graphene in electronic applications January 14th, 2015

Announcements

Industrial Nanotech, Inc. Announces New OEM Customer January 27th, 2015

Carbon nanoballs can greatly contribute to sustainable energy supply January 27th, 2015

The laser pulse that gets shorter all by itself: Ultrashort laser pulses have become an indispensable tool for atomic and molecular research; A new technology makes creating short infrared pulses easy and cheap January 27th, 2015

New pathway to valleytronics January 27th, 2015

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE