IoT workshop - Is 1kV Also Enough for IoT ESD Protection – Do Current Test Methods and Models Apply?

KOEN VERHAEGE, SOFICS – SEPTEMBER 27, 2018
Is 1kV enough for IoT ESD protection?
Do current test methods and models apply?
IoT WORKSHOP

SOFICS © 2018 Proprietary & Confidential 2
• Problem statement
• Challenges for IoT semiconductor design
• Risk analysis
• Case studies
• Conclusions

Problem statement – why these 2 questions?
• A brief history of ESD demands…
– Year 2000: typical requirements: 2kV HBM, 200V MM, 1kV CDM
 Weakest pin defines the ESD qualification of the IC
 Focus on production and assembly – unpowered packaged IC in controlled environment
– Year 2008: pin exceptions & non-standardized tests
 Corner pins (lower CDM on other pins)
 High speed/RF pins (trade robustness for speed)
 External connections like USB, HDMI… (5..10X higher robustness)
 HBM/MM on (powered) IC supply lines

• A brief history of ESD demands… (continued)
– Year 2016: diverging trends & creative testing
 Lowering of “historic” levels… 1kV is enough (for manufacturing)
– Avoid that “weakest design defines the specification”…
 Increasing specialty demands… anything from 100V to 24kV HBM…
 System, automotive, surge requirements addressing various ESD, EOS, LU, EMC aspects
 Creative (overkill) testing
– CDM on die or wafer
– Cut cable testing for interfaces
– System stress on device
– Powered zap-gun testing for transient LU

• Voice of the ESD community
– Mitigation of ESD hazards
 Control (in manufacturing) – ANSI ESDA 20.20
 Design – technology progress/challenges
How can I make my ESD mitigation more/most cost effective?
• Voice of the customer of the ESD community
– Omnipresence and use of electronics
 New applications
 New environments
 New packaging and form factors
Will my product be reliable and robust enough?

• Risk analysis
• Case studies
• Conclusions

Challenges for IoT semiconductor design
• Internet of Things
– Network of physical devices
– Embedded with electronics
– Collecting and exchanging data
– Endless opportunities
• Billions of those “Things”
– Cisco: 50 billion devices by 2020
– Everywhere, everything

Challenges for IoT semiconductor design
• (Wireless) connectivity
• Standards (compatibility)
• Security
• Privacy
• Sensor integration
• Cost reduction
• High performance
• Low power consumption
• Small form factor
• Silicon/system packaging
• Robustness
• Reliability

• Risk analysis
• Case studies
• Conclusions

Risk analysis – ISO 31000
• Risk assesment matrix
– Identify threats
– Assess vulnerability
– Determine likelihood
– Determine impact
– Define risk and mitigation
Impact
RISK
Negligible
[1]
Minor
[2]
Serious
[3]
Critical
[4]
Catastrophic
[5]
Likelihood
Extremely
unlikely
[A]
None Trivial Low
Below
moderate
Moderate
Remote
[B]
Trivial Low
Below
moderate
Moderate Tolerable
Occasional
[C]
Low
Below
moderate
Moderate Tolerable Substantial
Reasonably
possible
[D]
Below
moderate
Moderate Tolerable Substantial Major
Frequent
[E]
Moderate Tolerable Substantial Major Intolerable

Risk analysis – threats
• Identify the IoT threats
– (Daily and/or uncontrolled) use
 Smart device handling as a dummy
– Use locations
 Remote, embedded...
– (Harsh) environments
 Non-standard electrical overstress
 EMI
 Noise
www.anttix.com/articles/devices-devices-everywhere

Risk analysis – vulnerability
• Vulnerability
– (High speed) data connection
 Sensitive gates (thin oxide)
 Antennas
 Signal integrity
– Shielding
 Exposed connectors
– Form factor
 Short on-board distances
 (Omission of) TVS
– Packaging
 Non-standard die bonding / connection
• Vulnerability assessment
– Traditional device level methods
 HBM, CDM
 Latch-up
– System level
 IEC 61000-4-2 (HBM)
 IEC 61000-4-5 (surge)
 EMC
– Custom setups
 EOS
 Powered IC testing
 Transient LU

Risk analysis – likelihood
• ESD exposure well covered by traditional approaches during...
– Manufacturing
– IC assembly
– IoT assembly
One 1kV and traditional models are likely enough... provided good ESD control is in place
• ESD exposure more likely and more unknown during...
– Functional operation in varying environments, locations and applications

Risk analysis – impact
• General:
– Soft errors
 Sometimes reset required
– Hard failures
 Permanent physical defect
• Different impact for different IoT applications
– Result can range from annoying to... lethal
 Safety/security, person vs. thing
– Replacement or reset is not always possible
 In-body applications
 Distributed networks with (millions of) (remote) sensors

Risk analysis – adequate protection
Impact
RISK Negligible
[1]
Minor
[2]
Serious
[3]
Critical
[4]
Catastrophic
[5]
Likelihood
Extremely
unlikely
[A]
None Trivial Low
Below
moderate
Moderate
Remote
[B]
Trivial Low
Below
moderate
Moderate Tolerable
Occasional
[C]
Low
Below
moderate
Moderate Tolerable Substantial
Reasonably
possible
[D]
Below
moderate
Moderate Tolerable Substantial Major
Frequent
[E]
Moderate Tolerable Substantial Major Intolerable

• Risk analysis
• Case studies
– 7 EOS/ESD protected IoT applications
• Conclusions

Case 1: IoT at the cloud side
• IoT connectivity for billions of ‘things’
occurs via the cloud consisting of…
– About 8M data centers worldwide
– Multiple 10K servers per data center
• Server network connections
– Short and long distances
– (Very) high speed
 10-100 gigabit-per-second
– Optical communication
 Silicon Photonics

• Silicon Photonics: 2.5D/3D integration
– Silicon IC (logic) in advanced nano-CMOS
– Photonic IC in mature SOI process
• ESD risk assessment: low
– Threat: ESD controlled area and use
– Vulnerability: high speed pins
– Likelihood: A – B – C – D – E
– Impact: 1 – 2 – 3 – 4 – 5

• Stress model selected:
– HBM (ANSI/ESDA STM5.1)
• Protection level specified:
– 2kV most I/Os > standard available
– 200V high speed I/O > per low cap requirement
• Custom ESD solution applied
– Sensitive 0.9V thin oxide transistors
 TSMC 28nm and 16nm (1st and 2nd gen. product)
– Ultra-low parasitic capacitance below 15fF
 Protection of high speed (56Gbps) pins

Case 2: industrial, indoor positioning
• Positioning sensors – RF tagging
– Industrial use, many locations
– 802.15.4a standard
– 8.5GHz wireless interface
– 10 year lifetime from 1 coin battery
• ESD risk assessment: below moderate
– Threat: industrial use and environment
– Vulnerability: package, form factor
– Impact: 1 – 2 – 3 – 4 – 5

Case 2: industrial, indoor positioning
– 2kV incl. wireless I/O > by customer choice
– Sensitive thin oxide transistors
 TSMC 90nm and 40nm (1st and 2nd gen. product)
– Low parasitic capacitance below 100fF
 Protection of high bandwidth (8.5GHz) pins
– Low leakage below 100pA
 10 years on 1 coin battery

Case 3: Near Field Communication (NFC)
• NFC: simplify everyday tasks
– Payment
– Transportation
– Networking
– Promotions/coupons
• ESD risk assessment: moderate
– Threat: daily/everywhere use/environment
– Vulnerability: signal integrity, antenna
– Impact: 1 – 2 – 3 – 4 – 5

Case 3: Near Field Communication (NFC)
– EOS
– 2kV HBM
– 10V EOS
• Custom EOS/ESD solution applied
– Sensitive thin oxide transistors (no HV)
 55nm – 9V signal to be clipped at 3.6V
– Voltage at receiver depends on proximity
 Signal shape preserved – no HF distortions
3.6V antenna
clipping

Case 4: body implanted devices
• Implanted hearing aid
– Wireless connection for signal and power
– High voltage electrode / stimulus
– Low power design
• ESD risk assessment: moderate
– Threat: shielded embedded use
– Vulnerability: 18V electrodes
– Impact: 1 – 2 – 3 – 4 – 5

Case 4: body implanted devices
– 6kV for 18V electrode pins > human use consideration
– High voltage tolerance up to 18V
 Stimulation of nerves
– Ultra-low power design
 Leakage of ESD clamp around 10pA @37°C

Case 4: other networked medical devices
• Likelihood and impact differ significantly between applications
– Wearable, external devices have higher likelihood of ESD events
– Life supporting devices (pacemakers) have a bigger impact if things go wrong
Impact
RISK [1] [2] [3] [4] [5]
Likelihood
[A]
[B]
[C]
[D]
[E]

Case 5: wearable devices
• Wearable fitness tracker
– Bluetooth connection
– Wireless GPS
– MEMS gyroscope
– Low power requirement
• ESD risk assessment: tolerable
– Threat: every day use/environment
– Vulnerability: signal integrity or loss
– Impact: 1 – 2 – 3 – 4 – 5

Case 5: wearable devices
– 2kV HBM
– Sensitive thin oxide transistors
 TSMC 55nm
– Low parasitic capacitance below 150fF
– Over voltage 5V tolerant analog I/O
 USB connection

Case 6: smart home
• Internet enabled button / sensor
– Wifi connected
– Low power
– Wide variety of functions are possible
• ESD risk assessment: substantial
– Threat: every day use/environment
– Vulnerability: form factor, packaging
– Impact: 1 – 2 – 3 – 4 – 5

Case 6: smart home
– IEC (61000-4-2)
– 15kV air discharge
– TSMC 180nm
– TLP current > 20A
– SCR based – viable on-chip area use
– Short connections on-board
TVS

Case 7: industry 4.0
• Sensors in factories
– Predictive maintenance
– Constant monitoring (T, p, freq...)
• ESD risk assessment: major
– Threat: noisy industrial environment
– Vulnerability: form factor, packaging
– Impact: 1 – 2 – 3 – 4 – 5

Case 7: industry 4.0
– IEC (61000-4-2)
– 15kV air discharge
– 15kV IEC 61000-4-2 air discharge
 Touch sensor node inside package
– Ultra-low power design – below 20nA
 20yr lifetime on single coin battery

• Risk analysis
• Case studies
• Conclusions

Conclusions
• ESDA roadmap for HBM levels
– Component level ESD protection
– Ensure the IC is safely produced and
integrated into the (IoT) system
• Some IoT applications demand a
different robustness to prevent failure
during functional operation
– Often HBM is used for this purpose
– IEC tests for higher risk applications
– EOS tests for specific applications

Conclusions
• Is 1kV enough for IoT ESD protection?
– Risk depends on application and process
– Additional trade-offs add complexity
– Not possible to apply a “one spec fits all” ESD stress requirement
• Do current test methods and models apply?
– Frequently additional reliability or custom test methods are required
– Include EOS/ESD consideration early in the design phase to identify solutions for new threats

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www.sofics.com

IoT workshop - Is 1kV Also Enough for IoT ESD Protection – Do Current Test Methods and Models Apply?

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