Parasitic SCR ESD Protection in Semiconductor Devices

Solution Overview

Problem

Existing ESD protection devices using diode strings and silicon controlled rectifiers (SCRs) face challenges in efficiently managing transient voltages during electrostatic discharge (ESD) due to the need for thin gate oxides and low supply voltages, which require extreme limitations on voltage levels and current handling.

Innovation Solution

A semiconductor structure is designed with a parasitic silicon controlled rectifier (SCR) formed between two devices, allowing for tunable trigger and holding voltages by adjusting the number and placement of diodes, enabling efficient ESD protection without activating external diode strings, and utilizing the inherent properties of the SCR for high-performance ESD management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If thin gate oxides are used to increase drive current and circuit speed, then circuit performance is improved, but the device becomes extremely sensitive to transient voltages during ESD current

Engineering Contradiction:

Improvecircuit speedVSAvoidsensitivity to transient voltages

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The SCR is configured to trigger at a predetermined voltage threshold (Vtrigger) before the thin gate oxide can be damaged by excessive transient voltages. This preliminary protective action clamps the voltage to safe levels, allowing the use of thin gate oxides for high-speed operation without exposing them to harmful voltage transients during ESD events.

Inventive Principle:

Principle #10Preliminary action

2Duration of action of stationary object

If low supply voltages are used to reduce hot carrier effects, then device lifetime is extended, but the ability to handle ESD current is limited

Engineering Contradiction:

Improvedevice lifetimeVSAvoidESD current handling capability

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The SCR is designed to convert the harmful ESD current into a beneficial protective mechanism. When ESD current flows, the SCR triggers and clamps the voltage to a safe holding voltage (Vhold), transforming the potentially damaging high-voltage transient into a controlled, low-voltage state that protects the low-supply-voltage circuit while maintaining device lifetime.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If a diode string is used to trigger the SCR, then ESD protection is activated, but the diode string conducts only trigger current and cannot handle the full ESD current

Engineering Contradiction:

ImproveESD protection activationVSAvoidcurrent handling capability

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The ESD protection function is segmented into two distinct roles: the diode string handles only the trigger current to activate the SCR, while the SCR itself handles the full ESD current. This segmentation allows each component to be optimized for its specific function, with the SCR providing the high current handling capability needed for ESD protection while the diode string provides reliable triggering.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution provides enhanced ESD performance by allowing for flexible design and efficient current handling, effectively clamping voltages to a holding voltage of approximately 1.2V and triggering at specific voltage levels, thereby improving the protection capabilities within the ESD design window.

Implementation Method 1

The solution provides enhanced ESD performance by allowing for flexible design and efficient current handling, effectively clamping voltages to a holding voltage of approximately 1.2V and triggering at specific voltage levels

Methodology Applied

Scientific EffectSilicon controlled rectifier (SCR) voltage clamping:

Implementation Method 2

A semiconductor structure is designed with a parasitic silicon controlled rectifier (SCR) formed between two devices, allowing for tunable trigger and holding voltages by adjusting the number and placement of diodes, enabling efficient ESD protection without activating external diode strings

Methodology Applied

Scientific EffectParasitic SCR triggering:

Data Source

PatentUS7352014B2Semiconductor device based on a SCR

Publication Date: 2008.04.01 SOFICS BVBA

AI summary

The present invention provides a semiconductor structure device having a first and a second semiconductor devices with a silicon controlled rectifier (SCR) formed between the two devices with advantages to couple the devices to provide more design flexibility and enhanced triggering in order to improve the ESD performance of the device.