IGBT ESD Protection with Reverse Bias Device
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Solution Overview
Problem
Insulated gate bipolar transistors (IGBTs) used for electrostatic discharge (ESD) protection face issues with parasitic latch-up due to the formation of a low impedance path, which degrades the safe operating area and can cause unintended switching during normal operation, especially when high gate-to-source voltages are applied.
Innovation Solution
Incorporating a reverse bias device, such as a diode or a metal oxide semiconductor field effect transistor (MOSFET), in series with the IGBT to introduce a reverse bias and voltage drop across the emitter/source junction of parasitic bipolar junction transistors, preventing the formation of low impedance paths and enhancing the safe operating area by requiring an additional voltage drop to turn on the IGBT during ESD events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an IGBT is used for ESD protection, then ESD protection capability is improved, but parasitic latch-up occurs due to low impedance path formation
Solution Approach 1:
A reverse bias device (diode or MOSFET) is introduced as an intermediary component connected between the source terminal and body terminal of the IGBT. This intermediary device prevents the formation of low impedance paths by maintaining reverse bias conditions on the parasitic BJT junctions, thereby eliminating the parasitic latch-up effect while preserving the ESD protection function of the IGBT
Solution Approach 2:
The reverse bias device applies a preliminary counteracting influence by maintaining reverse bias on the parasitic BJT junctions before latch-up can occur. During normal operation and ESD events, the reverse bias device ensures that the voltage conditions necessary for parasitic latch-up (forward biasing of both BJT junctions) cannot be established, thus preventing the harmful effect in advance
2Reliability
If high gate-to-source voltages are applied to the IGBT, then ESD protection effectiveness is improved, but unintended switching occurs during normal operation
Solution Approach 1:
The reverse bias device acts as a voltage mediator between the source and body terminals, controlling the voltage distribution such that high gate-to-source voltages during ESD events do not translate into unintended turn-on of the IGBT. The device maintains proper voltage relationships that prevent parasitic BJT activation while allowing effective ESD clamping
3Reliability
If a reverse bias device is added in series with the IGBT, then parasitic latch-up is mitigated, but device complexity increases
Solution Approach 1:
The reverse bias device is integrated into the IGBT structure by connecting it between existing terminals (source and body) rather than requiring completely separate components. This merging approach adds the necessary reverse bias functionality while minimizing the increase in device complexity by utilizing the existing terminal structure of the IGBT
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 presence of a reverse bias device effectively mitigates parasitic latch-up conditions, ensuring the IGBT operates safely and reliably by requiring a higher gate signal to turn on, thus preventing unintended switching and improving the overall safe operating area.
Implementation Method 1
Incorporating a reverse bias device, such as a diode or a metal oxide semiconductor field effect transistor (MOSFET), in series with the IGBT to introduce a reverse bias and voltage drop across the emitter/source junction of parasitic bipolar junction transistors
Data Source
AI summary
In some examples, an electrostatic discharge (ESD) device comprises an insulated-gate bipolar transistor (IGBT) comprising a source terminal, an anode terminal, a gate terminal, and a body terminal; and at least one reverse bias device comprising a first terminal and a second terminal, wherein the first terminal couples to the source terminal and the second terminal couples to the body terminal.