Power MOSFET having enhanced breakdown voltage
First Claim
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1. A power metal oxide semiconductor field effect transistor (MOSFET), comprising:
- a source region;
a drain region;
a gate;
a body region;
a drift region extending between said bad region and said drain region, to at least partially guide current from said drain region to said source region;
a dielectric wall formed of an insulator, said dielectric wall having opposing sides, one of its opposing sides extending in contact with said drift region, and an opposite one of its opposing sides connected to a low-resistance conducting region, isolated from said drain region by portion of said dielectric wall so that a voltage across said dielectric wall between its opposing sides exerts an electric field into said drift region to redistribute free carriers in said drift region and thereby affect the electrical field distribution in said drift region to increase the breakdown voltage of a reverse biased semiconductor junction between said drift region and said body region;
wherein said dielectric wall is formed having a thickness tox, so that the relationship Nd≈
[(ε
si·
E02·
ε
ox4/3)/(2·
q7/3)]3/7·
[tox·
w]−
4/7 is satisfied, where Nd is the concentration of dopant in said drift region, 2w is a width of said drift region, ε
ox is the dielectric constant for said dielectric wall, ε
si is the dielectric constant for said drift region, E0 is the electric field avalanche value for said drift region and q is the electron charge.
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Abstract
A MOSFET includes a dielectric, preferably in the form of a metal thick oxide that extends alongside the MOSFET'"'"'s drift region. A voltage across this dielectric between its opposing sides exerts an electric field into the drift region to modulate the drift region electric field distribution so as to increase the breakdown voltage of a reverse biased semiconductor junction between the drift region and body region. This allows for higher doping of the drift region, for a given breakdown voltage when compared to conventional MOSFETs.
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Citations
18 Claims
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1. A power metal oxide semiconductor field effect transistor (MOSFET), comprising:
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a source region;
a drain region;
a gate;
a body region;
a drift region extending between said bad region and said drain region, to at least partially guide current from said drain region to said source region;
a dielectric wall formed of an insulator, said dielectric wall having opposing sides, one of its opposing sides extending in contact with said drift region, and an opposite one of its opposing sides connected to a low-resistance conducting region, isolated from said drain region by portion of said dielectric wall so that a voltage across said dielectric wall between its opposing sides exerts an electric field into said drift region to redistribute free carriers in said drift region and thereby affect the electrical field distribution in said drift region to increase the breakdown voltage of a reverse biased semiconductor junction between said drift region and said body region;
wherein said dielectric wall is formed having a thickness tox, so that the relationship Nd≈
[(ε
si·
E02·
ε
ox4/3)/(2·
q7/3)]3/7·
[tox·
w]−
4/7 is satisfied, where Nd is the concentration of dopant in said drift region, 2w is a width of said drift region, ε
ox is the dielectric constant for said dielectric wall, ε
si is the dielectric constant for said drift region, E0 is the electric field avalanche value for said drift region and q is the electron charge. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An n-channel or p-channel power metal oxide semiconductor field effect transistor (MOSFET), comprising:
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a source region;
a drain region;
a gate;
a body region;
a drift region extending between said body region and drain region, to at least partially guide carriers from said source region to said drain region;
two dielectric columns formed of a substantially insulating material, each having opposing sides, one opposing side of each of said two dielectric columns extending in contact with said drift region, and an opposite one of said opposing sides of each of said dielectric columns electrically connected to a low-resistance conducting region, each low resistance conducting region isolated from said drift region and said drain region by one of said dielectric columns, so that a voltage across each of said two dielectric columns between its opposing sides exerts an electric field into said drift region to redistribute free carriers in said drift region and thereby affect the electrical field distribution in said drift region to increase the breakdown voltage of a reverse biased semiconductor junction between said drift region and said body region;
wherein each of said dielectric columns is formed having a thickness tox, so that the relationship Nd≈
[(ε
si·
E02·
ε
ox4/3)/(2·
q7/3)]3/7·
[tox·
w]−
4/7 is satisfied, where Nd is the concentration of dopant in said drift region, 2w is a width of said drift region, ε
ox is the dielectric constant for each of said dielectric columns, ε
si is the dielectric constant for said drift region, E0 is the electric field avalanche value for said drift region and q is the electron charge.
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10. A power metal oxide semiconductor field effect transistor (MOSFET), comprising:
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a source region;
a drain region;
a gate;
a body region;
a uniformly doped drift region extending between said body region and said drain region, to at least partially guide current from said drain region to said source region;
a dielectric wall formed of an insulator, said dielectric wall having opposing sides, one of its opposing sides extending in contact with said drift region, along the entire extent of said drift region between said drain region and said source region, and an opposite one of its opposing sides connected to a low-resistance conducting region, isolated from said drain region by a portion of said dielectric wall and having a thickness so that a voltage across said dielectric wall between its opposing sides exerts an electric field into said drift region to redistribute free carriers in said drift region and thereby affect the electrical field distribution in said drift region to increase the breakdown voltage of a reverse biased semiconductor junction between said drift region and said body region. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification
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Current AssigneeNational University of Singapore
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Original AssigneeNational University of Singapore
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InventorsYang, Xin, Liang, Yung Chii, Gan, Kian Paau, Samudra, Ganesh Shankar
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Primary Examiner(s)Prenty, Mark V.
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Application NumberUS10/162,137Publication NumberTime in Patent Office980 DaysField of Search257/339, 257/341, 257/343, 257/488US Class Current257/339CPC Class CodesH01L 21/02258 formation by anodic treatme...H01L 21/31675 of siliconH01L 29/0653 adjoining the input or outp...H01L 29/402 Field platesH01L 29/407 Recessed field plates, e.g....H01L 29/41741 for vertical or pseudo-vert...H01L 29/41766 with at least part of the s...H01L 29/7802 Vertical DMOS transistors, ...H01L 29/7813 with trench gate electrode,...
