LDMOS Transistor Field Plate Coupling Gate Electric Field Management
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Solution Overview
Problem
Lateral double diffused MOS (LDMOS) transistors face a trade-off between on-resistance and drain junction breakdown voltage, where increasing doping concentration in drift regions reduces the breakdown voltage, affecting the stable operation of smart power devices.
Innovation Solution
The design includes a substrate with source and drain regions, a gate insulation layer, a gate electrode, a first field plate extending towards the drain region, a coupling gate between the second contact and the first field plate, and a second field plate connected to the second field plate, which are electrically connected to manage the electric field distribution and suppress breakdown voltage degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentration of drift regions is increased to reduce on-resistance, then the on-resistance decreases, but the drain junction breakdown voltage is reduced
Solution Approach 1:
The patent applies local quality by creating different doping concentration zones within the drift region. A first doping concentration is used in the first drift region adjacent to the channel, while a second, lower doping concentration is used in the second drift region adjacent to the drain. This spatial variation in doping quality allows the structure to simultaneously achieve low on-resistance (through the higher doped first drift region) and high breakdown voltage (through the lower doped second drift region), thereby resolving the technical contradiction between these two parameters.
2Reliability
If the doping concentration of drift regions is increased to reduce on-resistance, then the on-resistance decreases, but the stable operation of smart power devices is affected
Solution Approach 1:
The patent implements local quality by establishing distinct doping profiles in different spatial zones of the drift region. The first drift region maintains a higher doping concentration to ensure low on-resistance and good electrical conductivity, while the second drift region uses a lower doping concentration to maintain high breakdown voltage and operational stability. This localized differentiation of doping quality enables the device to simultaneously achieve both low on-resistance and stable operation under high voltage conditions.
3Strength
If multiple field plates and coupling gates are added to manage electric field distribution, then the breakdown voltage is improved, but the device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the gate structure into multiple functional segments: a first field plate extending from the gate electrode, a coupling gate positioned between the second contact and the first field plate, and a second field plate disposed between the coupling gate and the first field plate. This segmented configuration allows each component to perform a specific function in managing electric field distribution, with the coupling gate electrically connected to the second contact and the second field plate electrically connected to the coupling gate. The segmentation enables improved breakdown voltage through controlled electric field distribution while maintaining a systematic and manageable device architecture.
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 configuration uniformly distributes the electric field, suppressing breakdown voltage degradation and maintaining the balance between on-resistance and breakdown voltage, enhancing the operational stability of LDMOS transistors.
Implementation Method 1
This configuration uniformly distributes the electric field, suppressing breakdown voltage degradation
Data Source
AI summary
A lateral double diffused MOS transistor including a substrate, a source region and a drain region disposed in the substrate, a first contact and a second contact connected to the source region and the drain region, respectively, a gate insulation layer and a gate electrode on the substrate, a first field plate extending from the gate electrode toward the drain region, a coupling gate disposed between the second contact and the first field plate on the substrate, the coupling gate having a coupling voltage by coupling operation with the second contact, and a second field plate disposed between the coupling gate and the first field plate on the substrate, the second field plate being electrically connected to the second field plate.