MOSFET Body Plug Structure to Suppress Parasitic BJT Turn-On
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices like MOSFETs face issues with parasitic bipolar junction transistor (BJT) turn-on, which can lead to avalanche breakdown and damage, and a trade-off between drain-source on-resistance and breakdown voltage, particularly in bidirectional MOSFETs with deeply embedded body regions.
Innovation Solution
A semiconductor device with a plug of higher conductivity than the body region, connected to improve electrical conductivity, reduce parasitic BJT turn-on, and facilitate even electrical connection, especially for deeply embedded regions, while optimizing drain-source on-resistance and breakdown voltage through RESURF and shield electrode arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the body region is deeply embedded to enable bidirectional operation, then bidirectional operation is achieved, but electrical connection with the body region becomes difficult and base resistance increases
Solution Approach 1:
A plug structure is introduced as an intermediary element to establish electrical connection with the deeply embedded body region. The plug extends into the body region from the surface, providing a reliable conduction path without requiring direct surface access to the body region, thus resolving the contradiction between deep embedding for bidirectional operation and reliable electrical connection.
2Adaptability or versatility
If the body region is deeply embedded, then bidirectional operation is enabled, but base resistance of parasitic BJT increases leading to potential turn-on
Solution Approach 1:
The plug acts as an intermediary conduction path that reduces the effective base resistance of the parasitic BJT by providing a low-resistance connection to the body region. This mitigates the harmful effect of parasitic BJT turn-on while preserving the bidirectional operation capability enabled by deep body region embedding.
Solution Approach 2:
The plug changes the electrical parameter (base resistance) of the parasitic BJT by providing an alternative conduction path. By modifying the resistance parameter through the addition of the plug structure, the harmful turn-on effect is suppressed while the bidirectional functionality is maintained.
3Power
If drift region doping is increased to reduce drain-source on-resistance, then R DS(on) decreases, but breakdown voltage BV DSS decreases
Solution Approach 1:
The plug provides localized high-conductivity path specifically in the body region where needed for reducing parasitic resistance, while the drift region maintains its original doping profile optimized for breakdown voltage. This spatial differentiation of conductivity enhancement resolves the contradiction between low on-resistance and high breakdown voltage.
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 plug enhances electrical conductivity, prevents parasitic BJT turn-on, improves device ruggedness, and optimizes drain-source parameters, enhancing unclamped inductive switching performance and reducing surface electric fields.
Implementation Method 1
The plug has a higher electrical conductivity than the third region and is operable to improve electrical conductivity of the third region
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A semiconductor device comprising a cell. The cell comprises: a first region of a first conductivity type, a second region of the first conductivity type, a third region of a second conductivity type opposite to the first conductivity type and operably coupled between the first region and the second region, a gate electrode operably coupled with the third region to selectively allow or prevent current flow between the first region and the second region via the third region, and a plug electrically connected with the third region. The plug has a higher electrical conductivity than the third region and is operable to improve electrical conductivity of the third region. The first conductivity type is one of p-type or n-type and the second conductivity type is another one of p-type or n-type.