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BART KEPPENS
SEPTEMBER 2015
On-chip ESD solutions for
Internet of Things
Intellectual Property
SOFICS © 2015 Proprietary & Confidential 2
As is the case with many published ESD design solutions, the techniques and protection solutions described in this presentation are protected by patents
and patents pending and cannot be copied freely.
Contact Sofics to discuss about a license for the Sofics technology.
PowerQubic, TakeCharge, and Sofics are trademarks of Sofics BVBA.
SOFICS © 2015 Proprietary & Confidential 3
Outline
• Introduction
– Internet of Things (IoT)
• Challenges, solutions for ESD/EOS protection
• Conclusion
Internet of Things
SOFICS © 2015 Proprietary & Confidential 4
• By 2020 Cisco expects 50 billion connected devices
– More than 6 devices per person
IoT: According to Synapse
SOFICS © 2015 Proprietary & Confidential 5
• To achieve 50 Billion devices in 5 year
– Must be cheap
Below $5
– Must be able to run multiple years on 1 or 2 coin batteries
100uA limit
Always ON block to wake up rest of the functions: max. 10uA standby current
– Reasonable high MIPS CPU in active mode
300 MHz
– Must be small form factor
Can be inserted everywhere: keys, shoes, ...
– Must have worldwide connectivity options
Synapse selected LTE
IoT: according to SMIC
SOFICS © 2015 Proprietary & Confidential 6
• IoT Process, IP platform, subsystems
– Adequate performance
200MHz CPU
– Ultra low power
<1uW
– Wireless connectivity
Bluetooth, Zigbee, NFC, GPS, LTE,
– Embedded NVM
Up to 2MB memory
– Sensor integration
SiP
– Security
• Select right technology node by market size and computing complexity
SOFICS © 2015 Proprietary & Confidential 7
Outline
• Introduction
• Challenges, solutions for ESD/EOS protection
– Wireless connectivity
– Ultra Low power
– Sensor integration
– Reliability
• Conclusion
Intro: Explosive growth of wireless interfaces
• Wireless interfaces: very diverse and growing
– Broad set of standards and versions
– Increasing bandwidth
SOFICS © 2015 Proprietary & Confidential 8
Intro: ESD protection influences RF performance
• Example: RF ESD protection
– Lower gain (S21)
– Higher noise figure (NF)
– Degraded input reflection coefficient (S11)
• Unique ESD solutions required
– Low parasitic capacitance
– Low pad resistance
– High Q factor
– Low leakage
SOFICS © 2015 Proprietary & Confidential 9
[12]
Approach 1: Plug-n-play
• Minimize parasitic capacitance of ESD devices
– Parasitic capacitance chosen not to degrade RF performance
– Most used approach:
dual diode and efficient power clamp
– Alternative:
Local protection clamps
Select optimal protection device [15-21]
SOFICS © 2015 Proprietary & Confidential 10
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 2 4 6 8 10
ggnMOS
LVTSCR
Cj(0
) [p
F]
It2 [A]
20m
50m
75m
100m
150m
200m
Approach 2: LC cancellation
• ESD protection using filters and cancellation
– LC resonator isolates the ESD protection device from the RF input
– Resonator is tuned to the operation frequency of the RF circuit
– Does not require high-Q ESD protection device
• References [10, 13, 22]
SOFICS © 2015 Proprietary & Confidential 11
Approach 3: ESD – RF co-design
• Full (or partial) circuit ESD co-design
– ESD protection is integrated in RF design
– More designer freedom
– Designer has to know both RF and ESD!
• References [23, 24]
SOFICS © 2015 Proprietary & Confidential 12
90nm product: 8.5 GHz LNA
• Application: RF - tagging
– 8.5GHz wireless interface
– Location aware
– 10 year lifetime from 1 coin battery
– 802.15.4a standard: Alternate PHY for Zigbee devices
• Protection concept
– Design window failure voltage: 11.4V
– Dual diode approach not possible
Only narrow Vdd connection available
– Local clamp
SCR triggered by dynamically biased MOS
SOFICS © 2015 Proprietary & Confidential 13
90nm product: Capacitive loading
• Parasitic capacitance: calculation based on foundry data
– Maximum 100fF allowed
SOFICS © 2015 Proprietary & Confidential 14
90nm product: Results
• ESD protection for LNA IO
– ESD: >2kV HBM
– Latch-up immune
– Low capacitive: <100fF
– Low leakage: <0.1nA
– Small area: <3000um2
– CUP: ESD under bond pad
SOFICS © 2015 Proprietary & Confidential 15
Example NFC
SOFICS © 2015 Proprietary & Confidential 16
• Simplify everyday tasks
– Payment
– Transportation
– Networking
– Promotions/coupons
NFC – Near Field Communication
SOFICS © 2015 Proprietary & Confidential 17
• Simplified circuit
NFC – Near Field Communication
SOFICS © 2015 Proprietary & Confidential 18
• Protection required for antenna pads
– ESD protection
During production and assembly
– EOS protection
Amplitude of coil voltage depends on proximity
Differential voltage on antenna pads can run high
SOFICS © 2015 Proprietary & Confidential 19
• Simulation of voltage difference between antenna pads
9V
High voltage on antenna pads
SOFICS © 2015 Proprietary & Confidential 20
• Solution 1:
– Use high voltage transistors for RF front-end
• Solution 2:
– Limit the voltage
– Typical solution: diode based limiting circuit
– Sofics solution: clipping circuit
Voltage at antenna pads needs to be ’clipped’
SOFICS © 2015 Proprietary & Confidential 21
• Basic clipping circuit // Over voltage protection // limiting circuits
Diode based limiting circuits
SOFICS © 2015 Proprietary & Confidential 22
• Disadvantages for the diode-based solutions
– Large diodes required determined by the maximum current
– Large leakage current during normal non-clipped operation
– Large Silicon footprint
– Fixed clipping level determined by number of diodes
– Multiple diodes: creation of many parasitic bipolars: Darlington, latch-up...
Sofics clipping circuit
SOFICS © 2015 Proprietary & Confidential 23
• Silicon/product proof TSMC 55nm
– Area: 5488 µm² (63.52µm x 86.40µm)
– Max. current: 100 mA
– Different options
Clips @ 3.6V (ENABLE_CLAMP is ON)
Clips @ 2.2V (ENABLE_2V2 is ON)
GPIO use (ENABLE_CLAMP is OFF)
– Leakage below 780nA in GPIO mode
– Temperature range: -40°C up to 100 °C
Sofics: Over voltage and ESD protection circuit
SOFICS © 2015 Proprietary & Confidential 24
• Reduce maximum voltage
– Clip at 3.6V
– Option to clip at 2.2V
– Protect sensitive circuit
• Included
– Different clipping levels
– Enable/Disable circuit
55nm clipping circuit
Without clipping circuit
Sofics clipping circuit
SOFICS © 2015 Proprietary & Confidential 25
Outline
• Introduction
• Challenges, solutions for ESD/EOS protection
– Wireless connectivity
– Ultra Low power
– Sensor integration
– Reliability
• Conclusion
Ultra low power
SOFICS © 2015 Proprietary & Confidential 26
• Internet of Things devices need ultra low power
– Conserve battery power
– Rely on energy harvesting
• Foundries develop new platforms
– Reduced leakage
– Improved efficiency
– 55nm ULP
– 90nm ULP
– 40nm ULP
– 28nm FD SOI
Ultra low power
SOFICS © 2015 Proprietary & Confidential 27
• But how can ESD protection help to achieve lower power?
– Standby power: Select low leakage concepts
– Dynamic power: Select ESD with low parasitic capacitance for interfaces
Examples: ESD protection with ultra low leakage
• Reduce ESD related leakage with Sofics ESD IP
– Example: 1.2V TSMC 40nm
ESD protection for RF LNA circuit
Leakage ~20pA at 1.2V at high temperature
– Example: 5V TSMC 180nm
ESD protection for overvoltage tolerant IO
Leakage ~10nA at 5V at high temperature
– Example: 65nm ESD cells
All kinds of voltage domains
All kinds of interface types
Leakage ~20nA at high temperature
28 SOFICS © 2015 Proprietary & Confidential
SOFICS © 2015 Proprietary & Confidential 29
Outline
• Introduction
• Challenges, solutions for ESD/EOS protection
– Wireless connectivity
– Ultra Low power
– Sensor integration
– Reliability
• Conclusion
IC technology trends – VDD levels reducing
• Technology scaling
– Reduction of core supply voltage continues
1.5V at 130nm
1.0V at 32nm
0.85V at 28nm
– Pace defined by ITRS
• Foundries further reduce Vdd levels for IoT platforms
• What about sensor connections?
SOFICS © 2015 Proprietary & Confidential 30
Ref: IEW 2010 – Christian Russ, Infineon
Sensor connections
• Sensor interfaces
– Need different voltage levels
E.g. Several mV to 20V or higher
Cannot be handled by General Purpose I/O interface circuits
Need analog expertise, level shifters, sensitive current/sense amplifiers
– Examples:
Small signals (order of a few mV or mA) captured by sensors
– Motion detection
– Touch detection
– …
Driving voltage for implanted chip to restore hearing in the order of 20V
Sarnoff Europe © 2008 Proprietary & Confidential
31
GPIO ESD concept not suitable for Analog I/O
SOFICS © 2015 Proprietary & Confidential 32
• Typical GPIO ESD protection concept
– ESD robust output drivers
Large NMOS/PMOS transistors
Silicide blocked drains
Integrated diodes
– Poly resistance between ESD and circuit
• Issues
– Prevent high speed circuits
– Prevent accurate current/voltage sensing
– High leakage current
– Large silicon area
– High parasitic capacitance
Solution: Typical Analog I/O – diode based approach
SOFICS © 2015 Proprietary & Confidential 33
• Traditional Analog I/O
– Simple concept
Diode from Vss to Pad
Diode from Pad to Vdd
– Needs efficient power clamp
– Good characteristics
Low leakage
Low parasitic capacitance
Small area
– BUT: room for improvement
Lowest capacitance???
Overvoltage tolerant???
Protection of sensitive nodes???
Solution: Local I/O clamp reduces total voltage drop
SOFICS © 2015 Proprietary & Confidential 34
• Local I/O clamp
– Strongly reduce voltage drop during ESD
– Many different device options
– Place power clamp in the I/O !?
• Concerns?
– Leakage current at I/O?
– Parasitic capacitance at I/O?
– Silicon footprint?
– Latch-up immunity?
Vdd
Vss
IN +
Analog front end
Example: high voltage interfaces in 28nm CMOS
SOFICS © 2015 Proprietary & Confidential 35
• Customer required different high voltage ranges in TSMC 28nm
0
0.5
1
1.5
2
2.5
3
0 2 4 6 8 10 12
10-12
10-10
10-8
10-6
10-4
10-2
I [A]
V [V]
Leakage current [A]
3.9V 5.5V 6.05V no DNW
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20 25
10-12
10-10
10-8
10-6
10-4
10-2
I [A]
V [V]
Leakage current [A]
3.9V with DNW
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20 25 30
10-12
10-10
10-8
10-6
10-4
10-2
I [A]
V [V]
Leakage current [A]
5.5V 6.05V with DNW
0
1
2
3
4
0 5 10 15 20 25
10-12
10-10
10-8
10-6
10-4
10-2
I [A]
V [V]
Leakage current [A]
13.2V with DNW
Other issues with supplies
SOFICS © 2015 Proprietary & Confidential 36
• To reduce power consumption
– Small circuit stays awake all the time
– Other circuits (sensing, control, communication) are switched off
Special consideration for ESD conditions between the powerlines
SOFICS © 2015 Proprietary & Confidential 37
Outline
• Introduction
• Challenges, solutions for ESD/EOS protection
– Wireless connectivity
– Ultra Low power
– Sensor integration
– Reliability
• Conclusion
Reliability required?
SOFICS © 2015 Proprietary & Confidential 38
• Do innovative IoT devices need lower or higher ESD performance?
– Harsh environments
Industrial IoT
Automotive IoT
Wearables, semiconductor integrated into clothes
Implanted electronics
– New materials, approaches
– What about latch-up?
Battery powered devices – not possible to replace the battery
Implanted devices
The automotive market
SOFICS © 2014 Proprietary & Confidential 39
• Trend: more electronics in harsh EMI/EOS automotive environments
– Electrification of systems
– New regulations
– New applications
• Trend: more semiconductors in light cars
– $300 [2013]
– $400 [2017]
• TAM:
– $30B i.e. 10% semi market
• Reliability challenges:
– Zero defect requirements
– Very long system lifetime
Automotive electronics: not an “easy ride”
SOFICS © 2014 Proprietary & Confidential 40
• Operation conditions different than consumer and industrial
• System (reliability) requirements are equally more stringent
– DC: 12V, 24V, 40V…
– Transient currents: several Amperes
Consumer Industrial Automotive
Temperature 0 to 40⁰C -10 to 70⁰C -40 to 160⁰C
Operation time 2 to 5 years 5 to 10 years up to 15 years
Humidity low environment 0% to 100%
Field failure rate <10% <<1% 0 failure
Supply ~ 1 year ~ 2 to 5 years up to 30 years
Automotive electronics: not an “easy ride”
SOFICS © 2014 Proprietary & Confidential 41
• Zero defect requirements
– Severe reliability tests and qualification
– Cost of errors over product(ion) life time
Early-built-in reliability
• Trend:
– OEM push reliability specifications on the IC
Adds complexity and cost to the IC
Source: Freescale, David Lopez
Source: Audi, Christian Lippert
Automotive electronics: not an “easy ride”
SOFICS © 2014 Proprietary & Confidential 42
• Severe reliability requirements passed on component and system level
– Above standard HBM, MM requirements
– Transient latch-up immune
-27V..+40V
– ESD under powered conditions
0V..+18V
– IEC 61000-4-2 system ESD
– ISO 7637-2 load dump pulse
– EMC IEC 62132 DPI
• Requirements strongly depend on application
– Automotive, industrial applications: IEC 61000-4-2, ISO 7637, IEC 62132 …
– Battery, power management: IEC 61000-4-2
Source: STMicroelectronics, Philippe Merceron
SOFICS © 2015 Proprietary & Confidential 43
Outline
• Introduction
• Challenges, solutions for ESD/EOS protection
• Conclusion
Conclusion
SOFICS © 2015 Proprietary & Confidential 44
• Many challenges for ESD protection in IoT devices
– Wireless connectivity requires low parasitic capacitance ESD
– Wireless interfaces like NFC require voltage limiting circuits
– Low power devices need low leakage ESD
– Sensor integration and embedded memory needs multi voltage support
• Sofics on-chip ESD protection solutions
– Verified on 10 foundries, broad set of applications
– Leakage in order of nA versus uA
– Parasitic capacitance: 200fF versus 1pF
– Flexible trigger condition: support for multiple voltage options
Typical key aspects mentioned for IoT
SOFICS © 2015 Proprietary & Confidential 45
• Adequate performance
– Efficient DSP/MCU/CPU cores
• Wireless connectivity
– All kind of radio’s: Bluetooth, Zigbee, NFC, Wifi, LTE
• Ultra Low Power
– Battery powered / energy harvesting / Latch-up immune
• Sensor integration
– Beyond any imagination...
• Embedded non volatile memory
– Code, data and security key storage
• Security
– Privacy protection, not possible to hack
• Reliability
• Cost
References
SOFICS © 2015 Proprietary & Confidential 46
Contact us for more information?
SOFICS © 2015 Proprietary & Confidential 47
Sofics website
IoT cases