Embedded Zener Diode SCR for Latch-Up Reduction
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Solution Overview
Problem
Silicon-controlled rectifiers (SCRs) face challenges with high susceptibility to latch-up and secondary breakdown during electrostatic discharge (ESD) events, leading to potential device failure, and traditional SCRs exhibit snapback and low holding voltage, which are not effectively controlled.
Innovation Solution
Embedding a Zener diode within the SCR structure allows for adjustable trigger and holding voltages, reducing snapback and susceptibility to latch-up by creating an additional current path and modifying the device's behavior during ESD events, thereby enhancing ESD immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a traditional SCR structure is used, then the device can switch large levels of power, but the device exhibits snapback and has low holding voltage that cannot be effectively controlled
Solution Approach 1:
The Zener diode is embedded within the SCR structure, with the Zener cathode coupled to the SCR gate and the Zener anode coupled to the SCR anode. This nested configuration allows the Zener diode to control the gate trigger voltage, thereby controlling the holding voltage of the SCR without compromising its power switching capability.
2Reliability
If a traditional SCR structure is used, then the device can provide ESD protection, but the device has high susceptibility to latch-up and secondary breakdown during ESD events
Solution Approach 1:
The Zener diode acts as an intermediary element that modifies the electrical characteristics between the SCR anode and gate. By embedding the Zener diode, the trigger voltage is increased and holding voltage is controlled, which prevents the SCR from entering latch-up mode during ESD events while maintaining ESD protection capability.
3Reliability
If the trigger voltage of the SCR is increased, then the susceptibility to latch-up is reduced, but the ESD protection response may be delayed
Solution Approach 1:
The Zener diode's breakdown voltage is selected to be slightly above the normal operating voltage but below the ESD voltage level. This parameter configuration allows the SCR to respond quickly to ESD events (when voltage exceeds Zener breakdown voltage) while maintaining higher trigger voltage for normal operation, thus preventing latch-up without delaying ESD protection response.
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 embedded Zener diode in SCRs provides flexible and controllable trigger and holding voltages, reducing the likelihood of snapback and secondary breakdown, and enhances ESD immunity, ensuring robust operation and higher avalanche current handling.
Implementation Method 1
In semiconductor device level, the electrostatic discharge (ESD) event may exert a voltage much higher than the maximum voltage rating of the device, and consequently may induce an electrical breakdown via avalanche of carriers
Data Source
AI summary
In one aspect, a silicon-controlled rectifier (SCR) includes a Zener diode embedded in the SCR. In another aspect, a laterally diffused metal oxide semiconductor (LDMOS) includes a Zener diode embedded in the LDMOS. In a further aspect, a lateral insulated-gate bipolar transistor (IGBT) includes a Zener diode embedded in the IGBT.