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Non-equilibrium phonons in silicon f...

Sinha, Sanjiv.

Non-equilibrium phonons in silicon field-effect transistors.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Non-equilibrium phonons in silicon field-effect transistors.
Author:	Sinha, Sanjiv.
Description:	107 p.
Notes:	Adviser: Kenneth E. Goodson.
Notes:	Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0514.
Contained By:	Dissertation Abstracts International66-01B.
Subject:	Engineering, Mechanical.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3162321
ISBN:	0496960148

Non-equilibrium phonons in silicon field-effect transistors.
Sinha, Sanjiv.

Non-equilibrium phonons in silicon field-effect transistors. - 107 p.

Adviser: Kenneth E. Goodson.

Thesis (Ph.D.)--Stanford University, 2005.

Electrons and holes scatter strongly with phonons to heat the lattice over nanometer length scales in the drain of a silicon transistor. Heat conduction from the drain is important for the performance and reliability of the device, but may be increasingly hindered in future nanotransistors due to sub-continuum phenomena. The first of these is a temperature slip near the heat source, which, according to the literature, would dominate the temperature rise in the device. Past work has also shown the possibility of a supra-thermal "hot" phonon population in the drain, which could control electron transport. We gage the importance of these two phenomena in the context of sub-100 nm transistors. Starting from the phonon Boltzmann transport equation, we develop a model for phonon conduction from the heat source in a transistor. The model splits the heat flux into two components: One due to the phonons thermalized by anharmonic scattering, and another due to the non-equilibrium phonons emitted at the source. By comparing the steady-state peak temperatures predicted by this "split-flux" model and the heat diffusion equation, we find a reduced thermal conductance in the vicinity of the heat source. This increases the peak temperature by 13% in a 90 nm gate-length bulk silicon transistor and by 30% in a 18 nm gate-length ultrathin-body silicon-on-insulator device. We further use molecular dynamics to investigate the decay of optical phonons that dominate the heat source. The simulations show that the decay of the g-type optical phonon is through a 3-phonon process involving a longitudinal acoustic and a zone-edge transverse acoustic mode. We use this insight to investigate transient hot phonon populations during a switching event using a system of rate equations. Our solution shows that the optical phonon is cooled by its relaxation into acoustic modes but that the occupation of the acoustic modes is sufficiently augmented to cause re-absorption by electrons. We find that the above phenomena can increase the leakage power at the limits of scaling by as much as an order of magnitude in a bulk device and by five times in a silicon-on-insulator device.

ISBN: 0496960148Subjects--Topical Terms:

212470
Engineering, Mechanical.

Non-equilibrium phonons in silicon field-effect transistors.
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245 1 0 $a Non-equilibrium phonons in silicon field-effect transistors.
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500 $a Adviser: Kenneth E. Goodson.
500 $a Source: Dissertation Abstracts International, Volume: 66-01, Section: B, page: 0514.
502 $a Thesis (Ph.D.)--Stanford University, 2005.
520 # $a Electrons and holes scatter strongly with phonons to heat the lattice over nanometer length scales in the drain of a silicon transistor. Heat conduction from the drain is important for the performance and reliability of the device, but may be increasingly hindered in future nanotransistors due to sub-continuum phenomena. The first of these is a temperature slip near the heat source, which, according to the literature, would dominate the temperature rise in the device. Past work has also shown the possibility of a supra-thermal "hot" phonon population in the drain, which could control electron transport. We gage the importance of these two phenomena in the context of sub-100 nm transistors. Starting from the phonon Boltzmann transport equation, we develop a model for phonon conduction from the heat source in a transistor. The model splits the heat flux into two components: One due to the phonons thermalized by anharmonic scattering, and another due to the non-equilibrium phonons emitted at the source. By comparing the steady-state peak temperatures predicted by this "split-flux" model and the heat diffusion equation, we find a reduced thermal conductance in the vicinity of the heat source. This increases the peak temperature by 13% in a 90 nm gate-length bulk silicon transistor and by 30% in a 18 nm gate-length ultrathin-body silicon-on-insulator device. We further use molecular dynamics to investigate the decay of optical phonons that dominate the heat source. The simulations show that the decay of the g-type optical phonon is through a 3-phonon process involving a longitudinal acoustic and a zone-edge transverse acoustic mode. We use this insight to investigate transient hot phonon populations during a switching event using a system of rate equations. Our solution shows that the optical phonon is cooled by its relaxation into acoustic modes but that the occupation of the acoustic modes is sufficiently augmented to cause re-absorption by electrons. We find that the above phenomena can increase the leakage power at the limits of scaling by as much as an order of magnitude in a bulk device and by five times in a silicon-on-insulator device.
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