View
215
Download
0
Category
Preview:
Citation preview
7/28/2019 AdvSemi_lec7 2013-05-01
1/35
Advanced
Semiconductor
Devices
Lecture 7
Advanced
Semiconductor
Devices
Lecture 7
7/28/2019 AdvSemi_lec7 2013-05-01
2/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Lecture outline
Review
Approximations for regions of operation
Surface potential model in moderate inversion
MOS Capacitor
MOS Capacitor in moderate inversion
Accurate capacitance model in all regions of operation
Surface potential and inversion charge
Three-terminal MOS structure
Quasi-Fermi potential
7/28/2019 AdvSemi_lec7 2013-05-01
3/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Voltage and charge balance
Total charge in semiconductor body
7/28/2019 AdvSemi_lec7 2013-05-01
4/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Flatband
Accumulation
Depletion and inversion
Regions of operation
7/28/2019 AdvSemi_lec7 2013-05-01
5/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Solution for gate voltage
7/28/2019 AdvSemi_lec7 2013-05-01
6/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Accumulation
Condition for charge accumulation
Approximate solution for charge accumulation
7/28/2019 AdvSemi_lec7 2013-05-01
7/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Depletion
Condition for depletion
Approximation for gate voltage in depletion
7/28/2019 AdvSemi_lec7 2013-05-01
8/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Inversion
7/28/2019 AdvSemi_lec7 2013-05-01
9/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Gate voltage and surface potential ininversion
7/28/2019 AdvSemi_lec7 2013-05-01
10/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Weak inversion
7/28/2019 AdvSemi_lec7 2013-05-01
11/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Weak inversion
On the border of moderate inversion
In weak inversion
7/28/2019 AdvSemi_lec7 2013-05-01
12/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Weak inversion
7/28/2019 AdvSemi_lec7 2013-05-01
13/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Strong inversion
7/28/2019 AdvSemi_lec7 2013-05-01
14/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Moderate inversion
Need a simple solution for semiconductor charges and
potentials in moderate inversion !!!
7/28/2019 AdvSemi_lec7 2013-05-01
15/35 V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Moderate and strong inversion
7/28/2019 AdvSemi_lec7 2013-05-01
16/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Moderate inversion
7/28/2019 AdvSemi_lec7 2013-05-01
17/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Approximation for surface potential inmoderate and strong inversion
Obtained explicit approximation for the surface potential as
a function of gate voltage in moderate and strong inversionregions!!!
7/28/2019 AdvSemi_lec7 2013-05-01
18/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Moderate and strong inversion
7/28/2019 AdvSemi_lec7 2013-05-01
19/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor
7/28/2019 AdvSemi_lec7 2013-05-01
20/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor
7/28/2019 AdvSemi_lec7 2013-05-01
21/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor
Need to differentiate a complex expression
Instead, consider different regions of operation
7/28/2019 AdvSemi_lec7 2013-05-01
22/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor in accumulation
Semiconductor charge capacitance exponentially increasing
for large negative surface potential
Therefore, in accumulation
7/28/2019 AdvSemi_lec7 2013-05-01
23/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor in depletion
7/28/2019 AdvSemi_lec7 2013-05-01
24/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor in depletion
MOS C it i d t d
7/28/2019 AdvSemi_lec7 2013-05-01
25/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor in moderate andstrong inversion
Use surface potential as a function of gate voltage in
moderate and strong inversion regions
7/28/2019 AdvSemi_lec7 2013-05-01
26/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Match with depletion capacitance
MOS Capacitor in moderate andstrong inversion
Match with moderate and strong inversion
7/28/2019 AdvSemi_lec7 2013-05-01
27/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor in all regions ofoperation
At high frequency measurements observe depletion capacitance
At low frequencies observe both depletion and inversion charges
7/28/2019 AdvSemi_lec7 2013-05-01
28/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
MOS Capacitor approximation indepletion and inversion
There seems to be a problem on the border with weak inversion
7/28/2019 AdvSemi_lec7 2013-05-01
29/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Need to account for both depletion charge and inversion
charge in weak inversion
MOS Capacitor in weak inversion
7/28/2019 AdvSemi_lec7 2013-05-01
30/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Obtained approximation that seems to work in all regions of
depletion and inversion
Problem: surface potential as explicit function of gate voltage
MOS Capacitor approximation in allregions of inversion
7/28/2019 AdvSemi_lec7 2013-05-01
31/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Surface potential
7/28/2019 AdvSemi_lec7 2013-05-01
32/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Inversion Charge
7/28/2019 AdvSemi_lec7 2013-05-01
33/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Three-terminal MOS structure
Th t i l MOS t t
7/28/2019 AdvSemi_lec7 2013-05-01
34/35
V. Ariel 2013 Advanced Semiconductor Devices Lecture 7
Three-terminal MOS structure energy bands
7/28/2019 AdvSemi_lec7 2013-05-01
35/35
Three-terminal MOS structure - charges
Recommended