Trench-Gate IGBT Gate Capacitance Control via Segmented Trenches
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Solution Overview
Problem
Trench-gate IGBTs face challenges in finely adjusting reverse transfer capacitance without degrading cell performance, leading to oscillations in switching waveforms and increased switching losses due to either excessively low or high capacitance levels.
Innovation Solution
The semiconductor device incorporates a unique structure with multiple trench gate electrodes and insulating films, allowing for independent adjustment of gate capacitance through a combination of trench designs and semiconductor region configurations, including a p-type region in the gate wiring lead-out region to manage capacitance and maintain breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the depth of trenches in the cell region is increased to increase reverse transfer capacitance, then the reverse transfer capacitance is improved, but the cell performance changes or deteriorates
Solution Approach 1:
The patent divides the gate capacitance control into two independent parts: trenches in the cell region (first region) and trenches in the gate wiring lead-out region (second region). This segmentation allows independent adjustment of reverse transfer capacitance through the second region's trenches without affecting cell performance in the first region, resolving the contradiction between increasing capacitance and maintaining cell performance.
2Stability of the object's composition
If the reverse transfer capacitance is made too low, then the switching waveform oscillates and cannot be controlled, but increasing the capacitance by adjusting trench depth affects cell performance
Solution Approach 1:
The patent extracts the gate capacitance adjustment function from the cell region trenches and relocates it to the gate wiring lead-out region trenches. This extraction allows the switching waveform stability to be controlled independently through the second region's trenches, eliminating the negative impact on cell performance while still achieving the desired capacitance level for waveform stability.
3Loss of energy
If the reverse transfer capacitance is made too high, then the switching loss increases, but the capacitance needs to be sufficient to prevent waveform oscillation
Solution Approach 1:
The patent creates a dynamic and flexible capacitance control system by providing multiple trenches in the gate wiring lead-out region that can be selectively formed or configured. This allows precise adjustment of reverse transfer capacitance to the optimal level needed for waveform stability, avoiding excessive capacitance that would increase switching loss, while maintaining the ability to control switching waveform stability.
Data Source
AI summary
A semiconductor device includes a trench-gate IGBT enabling the fine adjustment of a gate capacitance independent from cell performance. In a gate wiring lead-out region, a plurality of trenches is arranged spaced apart from each other in an X direction perpendicular to a Y direction. Each trench has a shape enclosed by a rectangular outer outline and a rectangular inner outline in plan view. A trench gate electrode is provided in each of the trenches so as to be electrically coupled to an extraction electrode. To obtain an adequate breakdown voltage between a collector and an emitter, the trenches are formed in a p-type floating region. An n−-type drift region is formed in a region located inside an inner outline of the trench in plan view, whereby a capacitance formed between the trench gate electrode and the n−-type drift region is used as the reverse transfer capacitance.