l. head//ece dept./rowan university engineering electromagnetics 1 0909.301.01 fall 2004 linda head...
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L. Head//ECE Dept./Rowan University
Engineering Engineering Electromagnetics 1Electromagnetics 1
0909.301.010909.301.01 Fall 2004Fall 2004
Linda HeadECE Department
Rowan University
http://engineering.rowan.edu/~shreek/fall04/eemag1/lectures/mosfets.ppt
INTRODUCTION TO MOSFETSINTRODUCTION TO MOSFETSOctober 6, 2004October 6, 2004
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L. Head//ECE Dept./Rowan University
Silicon - Four CasesSilicon - Four Cases
Si
Si Si
Si
Intrinsic Si - 0oK
P-type Si N-type Si
Si
Si Si
Si
h+ e -
Intrinsic Si - Room Temp
Si
Si Si
B-
h+
e -h+
Si
Si Si
+
e -
Ph
h+ e -
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L. Head//ECE Dept./Rowan University
Metal-Oxide-SemiconductorMetal-Oxide-SemiconductorCapacitorCapacitor
Metal SiO2
n+ polysilicon
p-type silicon
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L. Head//ECE Dept./Rowan University
Looks Like…….Looks Like…….Insulator
Conductor
Conductor
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L. Head//ECE Dept./Rowan University
The positive charge on the metal is matched by negative charge from the ions in the p-type semiconductor. The h+ just get pushed away from the interface between the insulator and the p-type semiconductor leaving only the “stuck” charged atoms. We call this the depletion region - we now have a 2-layer insulator.
+V
SiO2
Metal and Polysilicon
p-type Si
Gnd.
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L. Head//ECE Dept./Rowan University
Once a maximum width is reached for the “depletion region” the electrons in the material are attracted to the SiO2 / p-type Si interface and now there is an channel of electrons right underneath the SiO2
++V
SiO2
Metal and Polysilicon
p-type Si
Gnd.
Electron Channel
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L. Head//ECE Dept./Rowan University
MOSFET Operating RegionsMOSFET Operating Regions
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L. Head//ECE Dept./Rowan University
Depletion RegionDepletion Region
Al
Al
Aln+ Polysilicon
Si Si
Si
0.4 V 0 V
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L. Head//ECE Dept./Rowan University
Inversion Region Inversion Region 1.0 V 0 V0 V
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L. Head//ECE Dept./Rowan University
Linear RegionLinear Region0.25 V1 V
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L. Head//ECE Dept./Rowan University
Pinch-Off RegionPinch-Off Region1 V 1.5 V
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L. Head//ECE Dept./Rowan University
Things You Need To KnowThings You Need To Know
r(Si) = 11.8 r(SiO2) = 3.9
• The length of the “channel” is 1.
• The n+ source and drain, the polysilicon and the p+ semiconductor are metal-like conductors.