MOSFET Carrier Compensation Electrode for Switching Stability
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Solution Overview
Problem
Conventional MOSFETs exhibit irregularities in switching characteristics when turned off due to charge balance irregularities around the gate, leading to increased switching characteristics irregularities and feedback capacitance, which affects their performance in power conversion circuits.
Innovation Solution
A MOSFET design with a carrier compensation electrode between the gate electrode and the trench bottom, along with an insulation region separating the carrier compensation electrode from the trench walls and bottom, and a source electrode connected to the carrier compensation electrode, which minimizes displacement current flow into the gate electrode, thereby reducing the impact of charge balance irregularities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MOSFET structure with super junction is used, then low ON resistance and high withstand voltage are achieved, but irregularities in charge balance around the gate cause large irregularities in switching characteristics when turned off
Solution Approach 1:
A carrier compensation electrode is introduced as an intermediary component between the gate electrode and the trench bottom. This carrier compensation electrode serves as a mediator to compensate for charge balance irregularities in the n-type and p-type column regions, thereby reducing irregularities in switching characteristics when the MOSFET is turned off, while maintaining the conventional super junction structure for low ON resistance and high withstand voltage
2Ease of manufacture
If charge balance irregularity occurs in n-type and p-type column regions, then manufacturing simplicity is maintained, but large irregularity in switching characteristics occurs when MOSFET is turned off
Solution Approach 1:
The carrier compensation electrode is positioned and configured in advance to compensate for potential charge balance irregularities before they affect switching characteristics. By having this compensatory structure pre-established, the MOSFET can tolerate manufacturing variations in dopant amounts while maintaining consistent switching characteristics
3Device complexity
If gate electrode is positioned close to n-type column region, then device complexity is reduced, but displacement current flows into gate electrode causing switching irregularities
Solution Approach 1:
The carrier compensation electrode acts as an intermediary that intercepts displacement current before it can reach the gate electrode. This allows the gate electrode to remain positioned close to the n-type column region for structural simplicity, while the carrier compensation electrode compensates for the harmful displacement current effect
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 reduces switching characteristics irregularities and feedback capacitance, maintaining low ON resistance and high withstand voltage while minimizing the effect of charge balance irregularities, even when irregularities occur, and allows for cost-effective and compact electronic equipment design.
Implementation Method 1
a gate insulation film formed on inner peripheral surfaces of the trenches 122, and a gate electrode formed in the trenches 122 by way of the gate insulation films 124
Implementation Method 2
a carrier compensation electrode positioned between the gate electrode and the bottom of the trench 122... even when an irregularity exists in a charge balance around the gate, an irregularity in switching characteristics when the MOSFET is turned off can be decreased
Implementation Method 3
an insulation region disposed in the trench, the insulation region extending between the gate electrode and the carrier compensation electrode, and extending along the side walls and the bottom of the trench thus separating the carrier compensation electrode from the side walls and the bottom
Implementation Method 4
a source electrode positioned on a surface of the semiconductor base substrate on a first main surface side, the source electrode electrically connected to the source region and also electrically connected to the carrier compensation electrode
Data Source
AI summary
Provided is a MOSFET which includes: a semiconductor base substrate having an n-type column region and a p-type column region, a base region and a source region, wherein a super junction structure is formed of the n-type column region and the p-type column region; a trench having side walls and a bottom; a gate electrode formed in the trench by way of a gate insulation film; a carrier compensation electrode positioned between the gate electrode and the bottom of the trench; an insulation region separating the carrier compensation electrode from the side walls and the bottom; and a source electrode electrically connected to the source region and also electrically connected to the carrier compensation electrode. According to the MOSFET of the present invention, even when an irregularity in a charge balance occurs around the gate, an irregularity in switching characteristics when the MOSFET is turned off can be decreased.