BOBSBSTGS

Zener Diodes for ESD/EOS Protection

4. GaN-based LEDs need ESD/EOS Protection1. Basic Functions of Zener Diode

GaN Epi Structure ESD damaged LEDs ESD Endurance

Dead & Degraded LEDs by ESD StrikeESD/EOS : 38 %Fabrication : 26 %

Assembly : 14 %

Mobile Ion : 3 %Good : 4 %

Unknown: 15 %

10-3

10-2

10-1

RT 120 °C

Zener voltage (Vz )Leakage current (Ileak @ -4 V)ESD strength (> ±8 kV)Current drivability (>100 mA)Temperature coefficient (ΔVz/ΔT < a few mV/K)

Zener breakdown

- Tunneling probability(Θ)

- Tunneling current(Jn)

Jn=qvRn ΘvR: Richardson velocity

Key Device Parameters

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛−=Θ

ε

23

*234exp gE

qmh

60

80

100

2. ESD/EOS Models and Standards 5. Configuration for LED Protection

-10 -8 -6 -4 -2 0 2 410-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4 150 °C 180 °C

Cur

rent

(A)

Voltage (V)

Ileak

Tunneling

Rz

Vz

-10 -8 -6 -4 -2 0 2 4-100

-80

-60

-40

-20

0

20

40

60

Cur

rent

(mA

)

Voltage (V)

HBM

MM

IEC61000-4-2 : HBM + CDM

IEC61000-4-4 : EFT

Strong TransientVoltage(ESD, Surge, EFT) Weak

Clamped Voltage

Reverse

Forward

BypassExcessCurrent

Circuit/Deviceto protect

VP ~ ±8 kVVC <~ 20 V

Light emitting chip

ESD Protecting Diode

6. Effective Protection of GaN-based LEDs3. Species of Zener Diodes

IEC61000-4-5 : Lightning SurgeCDM

Single Chip DualPad Series Connection(Cathode to cathode)

LED

Zener

Single Chip DualPad Series Connection(Anode to Anode)

Zener

LED

Single Chip DualPad Parallel Connection

Zener

LED

GeneralConnection of ZenerDiode with LED chip

Zener

LED

6 Effective Protection of GaN based LEDs3 Species of Zener Diodes

Double Pad StructureSingle Pad Structure

N-Substrate

P+ P+

P-Substrate

N+ N+

N-Substrate

P+

P-Substrate

N+

Triple Pad Structure

Unidirectional

10-5

Room Temp. 10-1

ESD(HBM) Strength

LED only : ±0.3 ~±7 kV

LED+Zener : > ±8 kV

P-Substrate

N+ N+N+

N-Substrate

P+ P+P+

P-Substrate

P+

N-

N-Substrate

N+

P-

Triple Pad StructureBidirectional

0 1 2 3 4 5 6 7 8 910-9

10-8

10-7

10-6

Reverse Voltage 5 V 6 V 10 V

Rev

erse

Lea

kage

Cur

rent

(A)

ESD Voltage (kV)

BeforeESD Zap

with Zener diodeESD ±8kV, 5 times

without Zener diode

-20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 410-9

10-8

10-7

10-6

10-5

10-4

10-3

10-2

25 °C 70 °C 110 °C

ESD : ± 8.0 kV, 5 times

Cur

rent

(A)

Voltage (V)

LED+ZenerLED only

Various Applications

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Various Applications