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Ex7 3 PDF

The document calculates the threshold voltage (VT) of a silicon nMOSFET for different substrate voltages (VBS). It provides the equations and values used to calculate VT at VBS = -2.5 V as an example. A table is included that lists the calculated VT for VBS = -2.5 V, -5 V, -7.5 V, and -10 V.

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sushant sharma
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75 views1 page

Ex7 3 PDF

The document calculates the threshold voltage (VT) of a silicon nMOSFET for different substrate voltages (VBS). It provides the equations and values used to calculate VT at VBS = -2.5 V as an example. A table is included that lists the calculated VT for VBS = -2.5 V, -5 V, -7.5 V, and -10 V.

Uploaded by

sushant sharma
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Example 7.

3 Calculate the threshold voltage of a silicon nMOSFET when


applying a substrate voltage, VBS = 0, -2.5, -5, -7.5 and -10 V.
The capacitor has a substrate doping Na = 1017 cm-3 , a 20 nm
thick oxide (ε ox = 3.9 ε 0 ) and an aluminum gate (Φ M = 4.1 V).
Assume there is no fixed charge in the oxide or at the oxide-
silicon interface.
Solution The threshold voltage at VBS = -2.5 V equals:
γ V
VT = VT 0 + ( 1 + SB − 1)
2φ F 2φ F
0.75 2 .5
= −0.09 + ( 1+ − 1) = 0.73 V
2 × 0.42 2 × 0.42
Where the flatband voltage without substrate bias, VT0 , was
already calculated in example 6.2. The body effect parameter
was obtained from:
2ε s qN a 2 × 11.9 × 8.85 × 10 −14 ×1.6 × 10 −19 × 1017
γ = =
Cox 3.9 × 8.85 ×10 − 14 / 20 ×10 − 7
= 0.75 V -1/2
The threshold voltages for the different substrate voltages are
listed in the table below.
VBS = -2.5 V -5 V -7.5 V -10 V
VT 0.73 V 1.26 V 1.68 V 2.04 V

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