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BOB SBS TGS Zener Diodes for ESD/EOS Protection 4. GaN-based LEDs need ESD/EOS Protection 1. Basic Functions of Zener Diode GaN Epi Structure ESD damaged LEDs ESD Endurance Dead & Degraded LEDs by ESD Strike ESD/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 (I leak @ -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(J n ) J n =qv R n Θ v R : Richardson velocity Key Device Parameters ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎝ ⎛ − = Θ ε 2 3 * 2 3 4 exp g E q m h 60 80 100 2. ESD/EOS Models and Standards 5. Configuration for LED Protection -10 -8 -6 -4 -2 0 2 4 10 -12 10 -11 10 -10 10 -9 10 -8 10 -7 10 -6 10 -5 10 -4 150 °C 180 °C Current (A) Voltage (V) I leak Tunneling Rz Vz -10 -8 -6 -4 -2 0 2 4 -100 -80 -60 -40 -20 0 20 40 60 Current (mA) Voltage (V) HBM MM IEC61000-4-2 : HBM + CDM IEC61000-4-4 : EFT Strong Transient Voltage (ESD, Surge, EFT) Weak Clamped Voltage Reverse Forward Bypass Excess Current Circuit /Device to protect V P ~ ±8 kV V C <~ 20 V Light emitting chip ESD Protecting Diode 6. Effective Protection of GaN-based LEDs 3. Species of Zener Diodes IEC61000-4-5 : Lightning Surge CDM Single Chip Dual Pad Series Connection (Cathode to cathode) LED Zener Single Chip Dual Pad Series Connection (Anode to Anode) Zener LED Single Chip Dual Pad Parallel Connection Zener LED General Connection of Zener Diode with LED chip Zener LED Double Pad Structure Single 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 Structure Bidirectional 0 1 2 3 4 5 6 7 8 9 10 -9 10 -8 10 -7 10 -6 Reverse Voltage 5 V 6 V 10 V Reverse Leakage Current (A) ESD Voltage (kV) Before ESD Zap with Zener diode ESD ±8kV, 5 times without Zener diode -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 10 -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 Current (A) Voltage (V) LED+Zener LED only Various Applications 2008~2010 A Company of Faith and Modesty Sigetronics, Inc. http://www.sigetronics.com Various Applications
