Vertical Trench MOSFET Field Plate Resistance for Surge Voltage Control
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Solution Overview
Problem
In vertical transistors, there is a trade-off between breakdown voltage and on-resistance, and when increasing switching speed to reduce switching loss, the surge voltage generated in the body diode increases, leading to noise and reliability issues.
Innovation Solution
A semiconductor device with a vertical power MOSFET structure that includes a field plate electrode in a trench, where the electric resistance between the source electrode and the field plate electrode is varied to improve the trade-off between switching loss and surge voltage by setting different values for the first and second electric resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the impurity concentration in the drift region is increased to reduce on-resistance, then the on-resistance is reduced, but the breakdown voltage is reduced
Solution Approach 1:
The patent applies local quality by creating a non-uniform impurity concentration distribution in the drift region through ion implantation. The impurity concentration is locally increased in specific areas (near the body diode and in certain depth ranges) while maintaining lower concentrations in other areas, allowing simultaneous optimization of on-resistance and breakdown voltage by treating different regions with different doping characteristics
Solution Approach 2:
The patent changes the impurity concentration parameter in the drift region by performing ion implantation at specific energy levels (1 MeV and 2 MeV) and doses. This parameter modification allows the drift region to achieve an optimized balance between low on-resistance and high breakdown voltage, resolving the trade-off relationship between these two parameters
2Loss of energy
If the switching speed is increased to reduce switching loss, then the switching loss is reduced, but the surge voltage generated in the body diode increases
Solution Approach 1:
The patent applies preliminary anti-action by pre-modifying the body diode structure through ion implantation before the switching operation occurs. The implantation creates a modified region that actively counteracts the surge voltage generation mechanism, reducing the harmful effect even when high switching speeds are used. This preventive modification addresses the surge voltage issue before it arises during switching operations
Data Source
AI summary
A semiconductor device of an embodiment includes: a semiconductor layer having a first face and a second face, the semiconductor layer including a first trench and a second trench on a side of a first face; a first electrode on the side of the first face; a second electrode on the side of the second face; a first gate electrode in the first trench; a first field plate electrode electrically connected to the first electrode in the first trench, a second gate electrode in the second trench; and a second field plate electrode electrically connected to the first electrode in the second trench, a resistance between first electrode and second field plate is different from a resistance between first electrode and the first field plate electrode.