Trench Gate Insulation Thickness Variation for Field Control
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Solution Overview
Problem
Existing semiconductor devices with trench gate structures face challenges in reducing on-resistance while maintaining sufficient breakdown voltage, particularly due to electric field concentration at the corners of trench gate electrodes, which can lead to breakdown when high voltages are applied.
Innovation Solution
The semiconductor device incorporates a trench structure with a thicker insulating film between the gate electrode and the interface between the drift and base regions, compared to the interface between the source and base regions, and includes a counter electrode embedded in the insulating film to reduce electric field concentration and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the trench width and intervals between adjacent trenches are reduced to increase the number of gate electrodes in a unit area, then the on-resistance is reduced, but the electric field concentration at the trench corners becomes more severe, leading to reduced breakdown voltage
Solution Approach 1:
The insulating film thickness is made non-uniform, being thicker at the corner portions of the trench bottom where electric field concentration occurs. This local variation in insulating film thickness provides enhanced electric field distribution at the critical corner regions while maintaining the overall trench gate structure for high-density electrode arrangement.
Solution Approach 2:
A counter electrode is positioned at the bottom of the trench to preemptively counteract the harmful electric field concentration effect. This counter electrode creates a compensating electric field that balances the concentrated field at the trench corners, preventing breakdown before it occurs.
2Reliability
If a counter electrode with floating potential or potential electrically connected to source electrode is provided below the gate electrode, then the electric field concentration near the trench corner is suppressed, but the device structure becomes more complex
Solution Approach 1:
The counter electrode is integrated within the existing trench structure, sharing the same trench space with the gate electrode. This merging approach allows the counter electrode to perform its electric field balancing function without requiring separate structural elements, thereby limiting the increase in device complexity.
Solution Approach 2:
The counter electrode serves multiple functions: it acts as an electric field balancing element to suppress corner concentration, provides additional capacitance, and can be electrically connected to either the source or gate for different operational modes. This multi-functionality justifies its inclusion despite the added structural complexity.
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 effectively reduces on-resistance while ensuring a sufficient level of withstanding voltage by minimizing electric field concentration at the trench corners, thereby improving the overall performance of the semiconductor device.
Implementation Method 1
a thickness of the insulating film between the gate electrode and an interface between the drift region and the base region may be larger than a thickness of the insulating film between the gate electrode and an interface between the source region and the base region
Data Source
AI summary
A semiconductor device according to one or more embodiments may include: a drain region; a drift region positioned above the drain region; a base region positioned on the drift region; a trench positioned to abut the base region and the drift region; an insulating in the trench; a counter electrode embedded in the insulating film; a gate electrode positioned above the counter electrode and that is embedded in the insulating film; and a source region that abuts the base region and the trench, wherein a thickness of the insulating film between the gate electrode and an interface between the drift region and the base region is larger than a thickness of the insulating film between the gate electrode and an interface between the source region and the base region.