Contenu connexe Similaire à Optimizing I/O’s and ESD protection to reduce power consumption in SOI applications (20) 1. SOFICS © 2020 Proprietary & Confidential 1
BENJAMIN VAN CAMP -SOFICS
OPTIMIZING I/O’S AND ESD PROTECTION TO REDUCE
POWER CONSUMPTION IN SOI APPLICATIONS
D&R IP-SOC DAYS
2. An IC through the eyes of an ESD engineer
SOFICS © 2020 Proprietary & Confidential 2
GND
VDD
Output Input
4. I/O ESD architectures
SOFICS © 2020 Proprietary & Confidential 4
…
Leakage I/O to GND
Leakage I/O to VDD
Leakage VDD to GND
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
5. Dual diode Protection
SOFICS © 2020 Proprietary & Confidential 5
• ESD protection implications
– Simplest architecture
– For large design windows
• Signal voltage implications
– VI/O > GND - 0.3V
– VI/O < VDD + 0.3V
• Leakage
– I/O - > GND: Through reverse junction of diode
– I/O - > VDD: Through reverse junction of diode
– VDD -> GND: Determined by power clamp
VDD
GND
I/O
Leakage
I/O to GND
Leakage
I/O to VDD
Leakage
VDD to GND
7. Diode characteristics
SOFICS © 2020 Proprietary & Confidential 7
• Current capability:
– Forward: 20-50mA/um
– Reverse: 0.5mA/um
• Parasitics
– PNP to substrate
– Diode from substrate to cathode
• Current capability:
– Forward: 5-10mA/um
– Reverse: 0.2mA/um
• No Parasitics
Bulk SOI
8. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 1 2 3 4 5
Voltage [V]
Current [A]
Diode measurements
SOFICS © 2020 Proprietary & Confidential 8
65nm SOI
Diode perimeter: 80um
~9-10mA/um
0
0.5
1
1.5
2
2.5
3
3.5
0 0.5 1 1.5 2 2.5 3
Voltage [V]
Current [A]
65nm Bulk
Diode perimeter: 92um
~33mA/um
9. Diode – Reverse Leakage
SOFICS © 2020 Proprietary & Confidential 9
• Reverse diode are low leakage
– Measured in 65nm bulk
– Similar for all technologies
• Leakage @ 1.8V
– ~10pA for 25°C
– ~200pA for 125°C
10
-12
10
-10
10
-8
10
-6
10
-4
0 2 4 6 8 10 12 14 16
Voltage [V]
Current [A]
25°C
125°C Thermochuck
induced noise
1.8V
10. I/O ESD architectures
SOFICS © 2020 Proprietary & Confidential 10
…
Leakage I/O to GND
Leakage I/O to VDD
Leakage VDD to GND
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
11. Secondary Protection
SOFICS © 2020 Proprietary & Confidential 11
• ESD protection implications
– Simple architecture
Diodes take most of ESD current
Secondary protection limits voltage
– Secondary protection can be small
– For smaller design windows
– CDM sensitive pins
• Signal voltage implications
– VI/O > GND - 0.3V
– VI/O < VDD + 0.3V
Leakage
I/O to GND
Leakage
I/O to VDD
VDD
GND
I/O
Leakage
VDD to GND
12. Secondary Protection
SOFICS © 2020 Proprietary & Confidential 12
• Leakage
1. I/O - > GND:
Path 1: Through reverse junction of diode
Path 2: Through Secondary clamp
-> Assume small ggNMOS
2. I/O - > VDD:
Path 1: Through reverse junction of diode
Path 2: Through Secondary clamp
-> Assume small ggNMOS
3. VDD -> GND: Determined by power clamp
+ Sum of secondary clamps Typically
negligible
Leakage
I/O to GND
Leakage
I/O to VDD
Leakage
VDD to GND
VDD
GND
I/O
13. NMOS in Snapback – one slide explanation
SOFICS © 2020 Proprietary & Confidential 13
1. Gate Grounded
– Voltage increases
– No current flow
2. Breakdown voltage drain-substrate reached
– Avalanching at drain
– Small current flow from drain to GND
3. Voltage built up over substrate resistance
– Substrate- Source reaches 0.7V
– NPN turns on
– Avalanching voltage lowered
Snapback
I
V
I
V
I
V
1
2
3
14. NMOS in bulk technology – cross section
SOFICS © 2020 Proprietary & Confidential 14
• NMOS in bulk technology has a shared p-substrate
– Large volume for Heat dissipation
– This shared p-substrate will help to trigger all the fingers
15. SOI MOS
SOFICS © 2020 Proprietary & Confidential slide 15
• SOI MOS
– Less volume for heat dissipation
– Body regions are isolated No body coupling between fingers
A
A’
16. GGNMOS Measurements
SOFICS © 2020 Proprietary & Confidential slide 16
0
0.5
1
1.5
2
2.5
0 1 2 3 4 5 6
current [A]
voltage [V]
90nm bulk process
It2 ~ 6 mA/um
• Bulk NMOS much higher It2
– Bulk: 5-10 mA/um
– SOI: 1-3 mA/um
• Voltages comparable
– SOI devices slightly lower trigger and holding voltage
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5 3 3.5 4
current [A]
voltage [V]
90nm SOI process
It2 ~ 2.4 mA/um
17. SOI MOS devices - Degradation
SOFICS © 2020 Proprietary & Confidential 17
• Often degradation is seen
– Don’t use these devices Factor 10
ESD SOI MOS
Seen in many MOS
devices in SOI
18. SOI MOS Variation
SOFICS © 2020 Proprietary & Confidential 18
130nm SOI
Foundry ESD Solution
Measured over
multiple samples
Leakage ~few nA
or lower
19. I/O ESD architectures
SOFICS © 2020 Proprietary & Confidential 19
…
Leakage I/O to GND
Leakage I/O to VDD
Leakage VDD to GND
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
20. I/O signal conditions
SOFICS © 2020 Proprietary & Confidential 20
• ESD protection implications
– Local Clamp required
Takes all of ESD current
Needs to limit voltage
– Local clamp large
– For smallest design windows
– CDM sensitive pins
• Local clamp options
– ggNMOS
– SCR
Leakage
I/O to GND
Leakage
I/O to VDD Leakage
VDD to GND
VDD
GND
I/O
21. I/O signal conditions
SOFICS © 2020 Proprietary & Confidential 21
• Conditions that require (semi) local protection
– VI/O > VDD + 0.3V
– Supply can be powered down
Energy Saving mode
Cold Spare
– CMRR: no I/O – VDD capacitance allowed
• Leakage
1. I/O - > GND:
Path 1: Through reverse junction of diode
Path 2: Through local clamp
2. I/O - > VDD: None
3. VDD -> GND: Determined by power clamp
Leakage
I/O to GND
Leakage
I/O to VDD Leakage
VDD to GND
VDD
GND
I/O
22. Protection Device Example (1/3) – 1.2V in 90nm SOI
Proprietary & Confidential -- Sarnoff © 2005 slide 22
0
0.5
1
1.5
2
0 1 2 3 4 5 6 7
10
-12
10
-11
10
-10
10
-9
10
-8
10
-7
10
-6
voltage [V]
leakage current [A] @ 1.32V
current[A]
W=8x30um
Vt1 = 3.2V
• SCR based power clamp in SOI
– Vhold = 2V
– Vmax = 6.4V
– Imax=7.5 mA/um
– Ron = 586.7 Ohm.um
• Leakage ~ 0.5nA/um @ 25°C
23. Protection Device Example (2/3) - 22nm SOI
SOFICS © 2020 Proprietary & Confidential 23
• SCR Based clamps for different domains
1.2V-1.8V – 125°C
0.8V - 125°C
0.8V – 25°C
1.2V-1.8V –25°C
Leakage
ESD performance
24. Protection Device Example (3/3) - 3.3V in 130nm SOI
SOFICS © 2020 Proprietary & Confidential 24
• Specialized ggNMOS based clamp
– To lower leakage
– To avoid variation
11nA, FF, 125°C
200pA, TT, 25°C
same process
25. I/O ESD architectures
SOFICS © 2020 Proprietary & Confidential 25
…
Leakage I/O to GND
Leakage I/O to VDD
Leakage
VDD to GND
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
26. Power protection - Leakage
SOFICS © 2020 Proprietary & Confidential 26
• Choice of power clamp is important
– Dependent on leakage/power specifications
– Dependent on power up/down strategy
– Dependent on temperature range
22nm SOI
Clamp type 25°C 125°C
0.8V Rail clamp 80nA 6uA
1.8V Rail clamp 100nA uA
0.8V SCR based <0.5nA 20nA
1.8V SCR based <0.5nA 20nA
0.8V ggNMOS 2nA
1.8V ggNMOS 10nA
Leakage
VDD to GND
VDD
GND
I/O
27. Conclusion - Leakage
SOFICS © 2020 Proprietary & Confidential 27
• I/O to GND
– Low leakage
• I/O to VDD
– Low leakage IF
Vsignal < VDD at all times
• VDD to I/O
– Depends on power clamp
– < 1nA @ RT possible
• I/O to GND
– Depends on local clamp
– < 1nA @ RT possible
• I/O to VDD
– Low leakage IF
Vsignal < VDD at all times
• VDD to I/O
– Depends on power clamp
– < 1nA @ RT possible
• I/O to GND
– Depends on local clamp
– < 1nA @ RT possible
• I/O to VDD
– Low leakage IF
Vsignal < VDD at all times
• VDD to I/O
– Depends on power clamp
– < 1nA @ RT possible
VDD
GND
I/O
VDD
GND
I/O
VDD
GND
I/O
28. Contact us
SOFICS © 2019 Proprietary & Confidential 28
• Sofics contact
Koen Verhaege
Benjamin Van Camp
Bart Keppens
info@sofics.com
engineering office
Sint-Godelievestraat 32
9880 Aalter, Belgium
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