Semiconductor Layout for Avalanche Current Shunting
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Solution Overview
Problem
Modern semiconductor devices face challenges in maintaining a sufficient safe operation area (SOA) while reducing device size, as they are prone to breakdown under high operating voltages, leading to potential damage and performance degradation.
Innovation Solution
Incorporating a parasitic bipolar junction transistor (BJT) with a large base resistance into the semiconductor device, which shunts avalanche current to a bulk region, thereby mitigating damage and allowing the device to operate safely beyond its initial breakdown voltage without increasing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the device size is reduced to increase functional density, then the device can be miniaturized and more circuits can be integrated, but the device becomes more prone to breakdown under high operating voltages
Solution Approach 1:
A parasitic bipolar junction transistor (BJT) is introduced as an intermediary component between the drain and source regions. This parasitic BJT acts as a mediator that activates during avalanche breakdown to shunt current away from vulnerable regions, thereby protecting the device structure while maintaining miniaturization benefits
Solution Approach 2:
The invention converts the harmful avalanche breakdown phenomenon into a beneficial protective mechanism. By deliberately designing the parasitic BJT to activate during breakdown conditions, the harmful high-voltage stress is transformed into a controlled current-shunting action that protects the device, allowing operation beyond initial breakdown voltage limits
2Power
If the operating voltage is increased to meet power circuit requirements, then the power handling capability is improved, but the device reliability deteriorates due to insufficient breakdown withstand capability
Solution Approach 1:
The parasitic BJT is designed to convert the harmful avalanche breakdown into a beneficial protective mechanism. When breakdown occurs at high operating voltages, the parasitic BJT activates and shunts the avalanche current, transforming the potentially damaging event into a controlled current redistribution that protects the device while maintaining high power handling capability
Solution Approach 2:
The invention changes the electrical parameters of the device by introducing a parasitic BJT with specific base resistance characteristics. This parasitic structure modifies the current-voltage characteristics during breakdown, enabling the device to safely operate at higher voltages than the original breakdown voltage of the main transistor
3Reliability
If a parasitic BJT with large base resistance is incorporated to shunt avalanche current, then the breakdown voltage ruggedness is enhanced, but the device structure becomes more complex
Solution Approach 1:
The parasitic BJT is designed to be self-activating during avalanche breakdown conditions. The large base resistance of the parasitic BJT automatically generates the necessary base-emitter voltage to turn on the transistor when avalanche current flows, eliminating the need for external control circuits or additional complexity in the device structure
Solution Approach 2:
The parasitic BJT structure serves multiple functions: it acts as a normal transistor component during regular operation, serves as a voltage reference during breakdown, and functions as a current-shunting protection mechanism. This multi-functionality reduces the need for separate protection circuits, thereby limiting the increase in overall device complexity
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
This solution enhances device performance by safely handling high breakdown voltages and reducing the risk of damage, allowing the semiconductor device to restore normal operation after a voltage spike, thus increasing the actual breakdown voltage without additional area costs.
Implementation Method 1
a first avalanche current generated around a first transistor and shunted through the bulk region is greater than a second avalanche current generated around a second transistor and shunted through the bulk region
Data Source
AI summary
A method includes: receiving the semiconductor device, wherein the semiconductor device includes: a well region; a doped region; a plurality of gate electrodes; a plurality of source regions; and a plurality of drain regions, wherein the plurality of gate electrodes, the plurality of source region and the plurality of drain regions form a plurality of transistors; and a bulk region disposed in the doped region. A first distance measured between a first transistor of the plurality of transistors and the bulk region is greater than a second distance measured between a second transistor of the plurality of transistors and the bulk region. The method further includes: applying a first voltage to the plurality of drain regions, wherein a first avalanche current generated around the first transistor and shunted through the bulk region is greater than a second avalanche current generated around the second transistor and shunted through the bulk region.