MOSFET Trench Thermal Conduction for Current Detection Accuracy
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Solution Overview
Problem
Current current control semiconductor elements face issues with increased parasitic resistance, restricted circuit configurations, and larger layout areas due to the placement of sense MOSFETs within main MOSFETs, leading to decreased accuracy in current detection as temperature differences between the two MOSFETs increase with driving current.
Innovation Solution
A semiconductor element design where the main MOSFET is surrounded by a trench groove with a higher thermal conduction coefficient than the sense MOSFET, allowing for improved heat dissipation and reduced temperature differences, thus maintaining accurate current detection without the aforementioned issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sense MOSFET is disposed in the main MOSFET to perform current detection, then current detection function is achieved, but parasitic resistance increases and wiring layout is restricted
Solution Approach 1:
The invention extracts the sense MOSFET from the interior of the main MOSFET and places it outside, surrounded by its own trench groove. This separation eliminates the wiring layout restrictions and parasitic resistance issues caused by embedding the sense MOSFET within the main MOSFET structure, while still achieving accurate current detection through the sense ratio relationship between the two MOSFETs.
2Temperature
If the main MOSFET size is made larger to reduce current density, then heat dissipation improves, but the ratio of heat dissipation from peripheral region to heat generation becomes smaller
Solution Approach 1:
The invention segments the heat dissipation function by creating a dedicated trench groove around the main MOSFET that is thermally coupled to it. This trench groove acts as a separate heat dissipation pathway, allowing the main MOSFET to effectively dissipate heat through the trench structure regardless of its size, thereby maintaining efficient heat dissipation while preserving design flexibility.
3Measurement precision
If different trench groove structures are used for main MOSFET and sense MOSFET, then temperature difference between them is reduced, but manufacturing complexity increases
Solution Approach 1:
The invention applies local quality by making the trench groove surrounding the main MOSFET thermally conductive (with higher thermal conduction coefficient) while the trench groove around the sense MOSFET has standard thermal properties. This localized differentiation in thermal conductivity ensures the main MOSFET operates at a temperature closer to the sense MOSFET, improving measurement accuracy without requiring complete structural symmetry.
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 design enhances the accuracy of current detection by minimizing the change in sense ratio with respect to driving current changes, reducing parasitic resistance, and allowing for regular wiring layouts and unrestricted circuit configurations, while maintaining efficient heat dissipation and reducing chip costs.
Implementation Method 1
a thermal conduction coefficient of the first trench groove surrounding the main MOSFET is larger than a thermal conduction coefficient of the second trench groove surrounding the sense MOSFET
Data Source
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AI summary
Provided are a current control semiconductor element that decreases the driving current dependency of a sense ratio and increases the accuracy of current detection by a sense MOSFET, and a current control device using the same. A current control semiconductor element includes, disposed on the same semiconductor chip, a main MOSFET for current drive and a sense MOSFET connected in parallel with the main MOSFET to detect a main MOSFET current. The main MOSFET and the sense MOSFET are formed so as to be surrounded by trench grooves with an insulating film embedded therein. The trench groove surrounding the main MOSFET has a width smaller than the width of the trench groove surrounding the sense MOSFET.