IGBT Trench Gate Structure for Loss Reduction
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Solution Overview
Problem
Existing IGBT designs face challenges with high on-state losses, low carrier enhancement, hole drain effects, and poor controllability due to their structural limitations, such as planar and trench gate electrode designs, which affect cell packing density, blocking capability, and switching losses.
Innovation Solution
The design incorporates a trench gate electrode separated by an insulating layer from the base and drift layers, with a deep well surrounded by an enhancement layer, allowing for improved carrier injection and reduced on-state losses, enhanced blocking capability, and better controllability through a self-aligned manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If planar gate electrode design is used, then manufacturing is simpler, but on-state losses increase due to carrier spreading and hole drain effects
Solution Approach 1:
The patent transitions from a planar gate electrode design to a trench gate electrode design that extends vertically into the drift layer. This dimensional change creates a vertical MOS channel that eliminates lateral carrier spreading and hole drain effects, thereby reducing on-state losses while maintaining manufacturability through established trench fabrication processes
2Loss of energy
If trench gate electrode design is used, then on-state losses are reduced, but blocking capability deteriorates due to high peak electric fields near trench bottom corners
Solution Approach 1:
The patent applies local quality by introducing a field oxide layer specifically at the bottom corners of the trench gate electrode where peak electric fields occur. This localized modification redistributes the electric field without affecting the overall vertical channel structure, thereby maintaining low on-state losses while improving blocking capability in the high-stress regions
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 configuration reduces on-state losses, improves blocking performance, and enhances controllability while simplifying the manufacturing process, resulting in a power semiconductor device with improved static and dynamic characteristics.
Implementation Method 1
the trench design offers a vertical MOS channel, which provides enhanced injection of electrons in the vertical direction
Implementation Method 2
an enhancement layer of a first conductivity type, which surrounds the base layer such that the enhancement layer completely separates the base layer from the drift layer and the well
Implementation Method 3
The trench gate electrode is separated from the base layer, the first source region and the drift layer by a first insulating layer
Data Source
AI summary
An IGBT has layers between emitter and collector sides. The layers include a collector layer on the collector side, a drift layer, a base layer of a second conductivity type, a first source region arranged on the base layer towards the emitter side, a trench gate electrode arranged lateral to the base layer and extending deeper into the drift layer than the base layer, a well arranged lateral to the base layer and extending deeper into the drift layer than the base layer, an enhancement layer surrounding the base layer so as to completely separate the base layer from the drift layer and the well, an electrically conducting layer covering the well and separated from the well by a second electrically insulating layer, and a third insulating layer having a recess on top of the electrically conducting layer such that the electrically conducting layer electrically contacts a emitter electrode.