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The influence of junction depth on short channel effects in vertical sidewall MOSFETs

The influence of junction depth on short channel effects in vertical sidewall MOSFETs
The influence of junction depth on short channel effects in vertical sidewall MOSFETs
This work addresses a fundamental problem of vertical MOSFETs, that is, inherently deep junctions that exacerbate short channel effects (SCEs). Due to the unconventional asymmetric junction depths in vertical MOSFETs, it is necessary to look separately at the electrostatic influence of each junction. In order to suppress short channel effects better, we explore the formation of a shallow drain junction. This is realized by a self-aligned oxide region, or junction stop US) which is formed at the pillar top and acts as a diffusion barrier for shallow junction formation. The benefits of using a JS structure in vertical MOSFETs are demonstrated by simulations which show clearly the effect of asymmetric junctions on SCEs and bulk punch-through. A critical point is identified, where control of SCEs by junction depth is lost and this leads to appropriate junction design in JS vertical sidewall MOSFETs. For a 70 nm channel length the JS structure improves charge sharing by 54 mV and DIBL by 46 mV. For body dopings of 5.0 x 10(17) cm(-3) and 6.0 x 10(17) cm(-3) the JS gives improvements in I-off of 58.7% and 37.8%, respectively, for a given I-on. The inclusion of a retrograde channel gives a further increase in I-on of 586 µA/µm for a body doping of 4.0 x 10(18) cm(-3).
1002-1007
Tan, L.
93a93652-be22-48a3-b4d0-b4e6605088d5
Buiu, O.
a994b22e-018b-4355-abd5-0227724f2a1a
Hall, S.
a11a8f8b-d6fb-47a7-82b1-1f76d2f170dc
Gill, E.
5da86de5-1169-403b-b81c-0b1b679f15f7
Uchino, T.
706196b8-2f2c-403d-97aa-2995eac8572b
Ashburn, P.
68cef6b7-205b-47aa-9efb-f1f09f5c1038
Tan, L.
93a93652-be22-48a3-b4d0-b4e6605088d5
Buiu, O.
a994b22e-018b-4355-abd5-0227724f2a1a
Hall, S.
a11a8f8b-d6fb-47a7-82b1-1f76d2f170dc
Gill, E.
5da86de5-1169-403b-b81c-0b1b679f15f7
Uchino, T.
706196b8-2f2c-403d-97aa-2995eac8572b
Ashburn, P.
68cef6b7-205b-47aa-9efb-f1f09f5c1038

Tan, L., Buiu, O., Hall, S., Gill, E., Uchino, T. and Ashburn, P. (2008) The influence of junction depth on short channel effects in vertical sidewall MOSFETs. Solid-State Electronics, 52, 1002-1007. (doi:10.1016/j.sse.2008.03.013).

Record type: Article

Abstract

This work addresses a fundamental problem of vertical MOSFETs, that is, inherently deep junctions that exacerbate short channel effects (SCEs). Due to the unconventional asymmetric junction depths in vertical MOSFETs, it is necessary to look separately at the electrostatic influence of each junction. In order to suppress short channel effects better, we explore the formation of a shallow drain junction. This is realized by a self-aligned oxide region, or junction stop US) which is formed at the pillar top and acts as a diffusion barrier for shallow junction formation. The benefits of using a JS structure in vertical MOSFETs are demonstrated by simulations which show clearly the effect of asymmetric junctions on SCEs and bulk punch-through. A critical point is identified, where control of SCEs by junction depth is lost and this leads to appropriate junction design in JS vertical sidewall MOSFETs. For a 70 nm channel length the JS structure improves charge sharing by 54 mV and DIBL by 46 mV. For body dopings of 5.0 x 10(17) cm(-3) and 6.0 x 10(17) cm(-3) the JS gives improvements in I-off of 58.7% and 37.8%, respectively, for a given I-on. The inclusion of a retrograde channel gives a further increase in I-on of 586 µA/µm for a body doping of 4.0 x 10(18) cm(-3).

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More information

Published date: 2008
Additional Information: Imported from ISI Web of Science
Organisations: Nanoelectronics and Nanotechnology

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Local EPrints ID: 269390
URI: https://eprints.soton.ac.uk/id/eprint/269390
PURE UUID: d2f4648f-c719-47f6-b5c0-ea74ef6ff75f

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Date deposited: 21 Apr 2010 07:46
Last modified: 16 Jul 2019 22:21

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Contributors

Author: L. Tan
Author: O. Buiu
Author: S. Hall
Author: E. Gill
Author: T. Uchino
Author: P. Ashburn

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