Concepts on ESD Protection Devices Vtr Safety Margin Vh Vtb Itb Voltage Ron Current Operation Range Oxide Breakdown Vox Vop V

Designing ESD Protection Network is … … to Optimize Resistor + Bypassing Components … in order to Control the ESD Current Influx as Desired. Current Flow in PS-Mode ESD Stress Zapping (+) Vss Vdd IO G Current Flow in PD-Mode ESD Stress Zapping Vss Vdd IO (+) G Current Flow in NS-Mode ESD Fluxing Situation Vss Vdd IO (-) G Current Flow in ND-Mode ESD Stress Zapping (-) Vss Vdd IO G

Classification of ESD Protection Components … Resistor & Gatekeeper Ground Ring Vss Power Vdd IO Local Protection Resd1 Resd2 VPNP LPNP LNPN Rsub Rwell Well Diode Cap Clamp Rpl Rpc Rgl Rgc P+ Diode N+ Diode Small Output Buffer Input Buffer Core Gatekeeper ESD Protection Device ( or Cell ) ESD Protection Resistor Parasitic Bus Resistance or Substrate Resistance Resistor … … Controls Quantity of Current Flux, and Build up (almost) Linear Voltage Drop upon Current Flow. … Has Neither Threshold Voltage Nor Preferential Polarity for Current Flow. Gatekeeper … … Determine Go-or-Stop of Current Flux, and Build up (usually) Non-Linear Voltage Drop upon Current Flow. … Has Both of Threshold Voltage and Preferential Polarity for Current Flow.

Resistor … Overall View ESD Protection Resistors ( Resd1, Resd2 ) are used … … Should be Maximized. … to Clamp ESD Stress Current. … to Build-Up Voltage on IO Pad. … to Protect IO Buffer Poly Resistor Diffusion Resistor Substrate / Well Resistors ( Rwell, Rsub ) are used … … Should be Optimized. … to invoke BJT Operation … to Control On-Resistance of BJT Operation Bus Resistors ( Rp1, Rp2, Rg1, Rg2 ) cause … … Should be Minimized. … Voltage Drop on Current Path Metallic Resistor Contact Resistor

Iesd Itb Vtb Ohmic Saturation Vesd Resistor … Current – Voltage Characteristics of ESD Protection Resistor Iesd Itb Vtb Ohmic Saturation Vesd Typically…, Either Poly Resistor or Diffusion Resistor are adopted as ESD Protection Resistors ( Resd1, Resd2 ). Both the Poly Resistor and the Diffusion Resistor tends to Show Current Saturation Behavior over Certain Critical Limit  Possible to Cut off Current Flow at High Current Limit, and also Possible to Build up High Voltage without Allowing Additional Current Flow.

Gatekeeper… General Qualifications Gatekeepers do … … Clamp the ESD Voltage / Shunt the ESD Stress Current. … Turn on Fast when ESD Stress is Applied. … Cope with Large Current for Quite a Long Time without Thermal Breakdown … Be Robust for Numerous Stress Pulses … Have Optimum On-State Resistance. … Occupy Minimum Area. … Have Minimum Capacitance. … Be Immune to Process Variation. … Not Interfere with IC’s Functioning at Normal Situation. … Not Cause Increased I/O leakage.

+ - - + + - - + - + - + + - + - - + - + Gatekeeper… Bilateral Passage Gatekeepers are to be equipped with (both) the (Parasitic) Diode (and the Parasitic BJT) operation. Forward Diode Reverse Diode + - - + N+/PW Diode + - - + P+/NW Diode BJT - + - + + - PMOS + - - + - + NMOS Avalanche Breakdown Operation

Forward Diode Operation Gatekeeper… Current – Voltage Characteristics Forward Diode Operation + - Voltage Current Vtr  0.6 ~ 1.0V + - + - + - Vop

Avalanche Breakdown Non-Snapback Operation Gatekeeper… Current – Voltage Characteristics Avalanche Breakdown Non-Snapback Operation - + Current - + - + - + (Vtb, Itb) Vtr - + Voltage Vop

Avalanche Breakdown Snapback Operation Gatekeeper… Current – Voltage Characteristics Avalanche Breakdown Snapback Operation Voltage Current (Vtb, Itb) Vtr Vh - + Vop

… or … Diode usually PMOS usually NMOS Gatekeeper… Typical Current-Voltage Characteristics Each Gatekeeper (Should) has the Current Voltage Characteristics like … Avalanche Breakdown Non-Snapback Operation Current Operation Range Oxide Breakdown Safety Margin … or … Forward Biased Diode Operation Vtr Safety Margin Vh Vtb Itb Voltage Ron Current Operation Range Oxide Breakdown Vox Vop V Forward Biased Diode Operation Avalanche Breakdown Snapback Operation Itb Ron Vtb V Vop Vh Vtr Vox Voltage Diode usually PMOS usually NMOS

Gatekeeper… ESD Protection Device Design Window Vtr Safety Margin Vh Vtb Itb Voltage Ron Current Operation Range Oxide Breakdown Vox Vop V Forward Biased Diode Operation Avalanche Breakdown Snapback Operation Small Leakage Current before Triggering Vtr < Vox , Vtb < Vox . Vop + V < Vh, Vtr Ron : Optimum Itb : Large Multi-Finger Triggering, Vtr  Vtb

( Total Inner Diffusion Perimeter = 30um) TLP Current –Voltage Characteristics of ESD Protection Devices … N+ / PW Diode 1.5V N+ / PW Diode ( Total Inner Diffusion Perimeter = 30um) Forward Diode Operation Reverse Diode Operation + - - +

( Total Inner Diffusion Perimeter = 30um) TLP Current –Voltage Characteristics of ESD Protection Devices … P+ / NW Diode 1.5V P+ / NW Diode ( Total Inner Diffusion Perimeter = 30um) Forward Diode Operation Reverse Diode Operation + - - +

( Total Inner Diffusion Width = 360um) TLP Current –Voltage Characteristics of ESD Protection Devices … GGPMOS 1.5V GGPMOS ( Total Inner Diffusion Width = 360um) Forward Diode Operation Non-Snapback BJT Operation + - - +

( Total Inner Diffusion Width = 360um) TLP Current –Voltage Characteristics of ESD Protection Devices … GGNMOS 1.5V GGNMOS ( Total Inner Diffusion Width = 360um) Forward Diode Operation Snapback BJT Operation + - - +

TLP Current –Voltage Characteristics of ESD Protection Devices … Overall 1.5V N+ / PW Diode 1.5V P+ / NW Diode + - - + + - - + + - + 1.5V GGPMOS 1.5V GGNMOS + - - + + -

Small Leakage Current before Triggering TLP Current –Voltage Characteristics of ESD Protection Devices … ESD Protection Device Design Window Vtr Safety Margin Vh Vtb Itb Voltage Ron Current Operation Range Oxide Breakdown Vox Vop V Forward Biased Diode Operation Avalanche Breakdown Snapback Operation Small Leakage Current before Triggering Vtr < Vox , Vtb < Vox . Vop + V < Vh, Vtr Ron : Optimum Itb : Large Multi-Finger Triggering, Vtr  Vtb LC (1.7V ) ~ 3E-10A Vtr  6.4V, Vtb  7.7V Vox > 10.0V Vop + V  1.7V, Vh  5.9V Vtr  7.7V 1.5V GGNMOS Rather Optimized Vop Vox Itb > 2.0A Vtr Vtr  6.4V, Vtb  7.7V

Kernel Rules for Gatekeeper ESD Protection Devices KG01. All the gatekeepers are to be equipped with (both) the (Parasitic) Diode (and the Parasitic BJT) Operation. The so called ‘N+ / PW Diode’ is equipped with Diode Operation. The so called ‘P+ / NW Diode‘ is equipped with Diode Operation. The so called ‘GGPMOS‘ is equipped with both the Parasitic Diode and Parasitic Non-Snapback ( or Weak Snapback ) BJT Operation. The so called ‘GGNMOS’ is equipped with both the Parasitic Diode and Parasitic Snapback BJT Operation. KG02. Triggering voltages of each operation generally complies following Order; Forward Diode Operation < BJT Operation < Reverse Diode Operation 0.6 ~ 1.0V < 5.0 ~ 7.0V < 10 ~ 12V ( Case of 1.5V Operation ) Gate Coupled MOS’ BJT Operation < Gate Floating MOS’ BJT Operation  Gate Grounded MOS’ BJT Operation KG03. Current immunity level of each operation shows following trends; Forward Diode Operation Excellent > BJT Operation Good > Reverse Diode Operation Worst ( Snapback BJT Operation is Better than Non-Snapback BJT Operation ) The ESD stress current has to be diverted only via Forward Diode Operation or BJT Operation of ESD Protection Gatekeeper Devices. In most cases, the ESD stress current diverted via Reverse diode Operation results in ESD failure. In most cases, the ESD stress current diverted via Core Devices results in ESD failure.