Super-junction MOSFET with Integrated Clamping Diodes
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Solution Overview
Problem
Super-junction MOSFETs face issues with thermal drift and high ON-state resistance due to parasitic bipolar transistor activation from overvoltages, leading to undesirable conduction during inhibition states, which existing solutions like clamping diodes do not fully address.
Innovation Solution
The integration of trench gates and internal diodes within the super-junction MOSFET structure, where the diodes are electrically connected in parallel to the MOSFET, allowing for electrical decoupling during inhibition states and reducing the likelihood of parasitic bipolar transistor activation, along with a manufacturing process that forms epitaxial layers with specific doping profiles to enhance junction characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clamping diodes are integrated in parallel to each parasitic bipolar transistor, then the activation voltage of parasitic bipolar transistors is increased, but the ON-state resistance becomes rather high
Solution Approach 1:
The patent merges the clamping diode function with the body region structure by forming the diode anode directly within the body region, eliminating the need for separate discrete diodes. This integration allows the same structural element to serve dual purposes: maintaining proper voltage clamping while preserving low ON-state resistance through optimized doping profiles and geometric configuration.
Solution Approach 2:
The patent applies local quality by creating specific doping regions with different concentrations within the body region. The anode region has a first doping concentration while adjacent regions have different doping concentrations, allowing each local area to be optimized for its specific function - the anode region for voltage clamping and adjacent regions for maintaining low ON-state resistance.
2Reliability
If overvoltages occur at the drain region, then parasitic bipolar transistors are activated causing thermal drift, but adding protective structures increases device complexity
Solution Approach 1:
The body region is designed to serve multiple functions simultaneously: it acts as the anode region for the clamping diode, provides the parasitic bipolar transistor base region, and maintains the super-junction structure for low ON-state resistance. This multi-functionality eliminates the need for separate protective structures that would increase device complexity.
Solution Approach 2:
The device uses its own inherent structures (body region, drain region, source region) to provide protection against overvoltages. The clamping diode is formed using the existing body region material and doping, allowing the device to protect itself without requiring external protective components or additional complex structures.
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 prevents thermal drift and improves the reliability and electrical performance of the super-junction MOSFET by reducing ON-state resistance and ensuring proper operation under overvoltage conditions.
Implementation Method 1
the gate layer 14 is biased at a gate voltage VG such as to generate respective channels 17 in each body region 9, in the proximity of the oxide layer 12, generating a respective flow of majority charge carriers (here electrons) 18
Implementation Method 2
The flows of electrons 20 cause undesirable heating of the body regions 9, and in particular of the conductive channels 17
Data Source
AI summary
A vertical-conduction MOSFET device, includes: a semiconductor body, having a front side and a back side and having a first conductivity; a trench-gate region; a body region, having the first conductivity; a source region, having a second conductivity; and a drain region, having the second conductivity. The source region, body region, and drain region are aligned with one another along a first direction and define a channel area, which, in a conduction state of the MOSFET device, hosts a conductive channel. The drain region borders on a portion of the semiconductor body having the first conductivity, thus forming a junction diode, which, in an inhibition state of the MOSFET device, is adapted to cause a leakage current to flow outside the channel area.