IGBT T-Trench Gate Segmentation for Loss Reduction
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Solution Overview
Problem
Existing power semiconductor devices, such as IGBTs, face challenges with high on-state and switching losses, poor blocking capability, and manufacturing complexity due to issues like carrier spreading, hole drain effects, and difficulties in applying field oxide layers, particularly in trench gate designs.
Innovation Solution
The introduction of T-trench gate electrodes with an enhancement layer that is electrically connected to the emitter electrode, allowing for better planarization and reduced on-state losses, improved blocking capability, and simplified manufacturing through a self-aligned process without the need for complex trench depth variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If trench gate electrodes are made wide and deep to reduce on-state losses, then carrier enhancement is improved, but manufacturing complexity increases and blocking capability deteriorates
Solution Approach 1:
The gate electrode structure is segmented into two functional parts: a controllable trench gate electrode (3) for carrier enhancement and injection, and a grounded gate electrode (4) with electrically conductive layer (42) for planarization and field control. This segmentation allows each part to be optimized independently, reducing the need for excessively deep or wide trenches while maintaining low on-state losses.
Solution Approach 2:
The grounded gate electrode (4) acts as an intermediary between the controllable trench gate electrode (3) and the drift layer (8). It provides the necessary planarization and electric field control without requiring the controllable gate to be excessively deep, thereby simplifying manufacturing while maintaining performance.
2Loss of energy
If trench gate electrodes are made wide and deep to improve carrier enhancement, then on-state losses are reduced, but blocking capability near trench bottom corners deteriorates due to high peak electric fields
Solution Approach 1:
The gate system is divided into controllable trench gate electrode (3) and grounded gate electrode (4), allowing the grounded electrode to handle field control and planarization functions that would otherwise require excessive depth in a single trench structure, thereby maintaining blocking capability.
Solution Approach 2:
The grounded gate electrode (4) and its electrically conductive layer (42) are maintained at emitter potential, creating an equipotential region that reduces peak electric fields near the trench bottom corners and improves blocking capability while still allowing the controllable trench gate to provide necessary carrier enhancement.
3Reliability
If planar gate electrodes are used with narrow cells and wide pitches, then blocking capability is maintained, but on-state losses increase due to carrier spreading and hole drain effects
Solution Approach 1:
The invention transitions from a purely planar gate design to a three-dimensional structure with trench gate electrode (3) extending vertically into the drift layer and grounded gate electrode (4) providing lateral planarization. This dimensional change enables better field control and reduced carrier spreading without compromising blocking capability.
Solution Approach 2:
Different regions of the gate structure are assigned different electrical properties: the trench gate electrode (3) region provides high field control for carrier injection, while the grounded gate electrode (4) with electrically conductive layer (42) provides low field regions for planarization and field control, optimizing both on-state and blocking performance locally.
4Loss of energy
If enhancement layers are added to reduce on-state losses, then carrier enhancement is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The grounded gate electrode (4) and its electrically conductive layer (42) combine multiple functions: they provide planarization, field control, and serve as a reference potential structure. This merged structure reduces the need for separate enhancement layers while still achieving low on-state losses.
Solution Approach 2:
The grounded gate electrode structure with electrically conductive layer automatically provides the field control and planarization functions that enhancement layers would otherwise need to provide, eliminating the need for additional enhancement layer processing steps and reducing overall device complexity.
Data Source
AI summary
An IGBT is provided having layers between an emitter electrode (2) on an emitter side (11) and a collector electrode (25) on a collector side (15), comprising: - a drift layer (8) of a first conductivity type, - a base layer (5), which electrically contacts the emitter electrode (2) and is completely separated from the drift layer (8), - a first source region (7), which is arranged on the base layer (6) towards the emitter side (11) and electrically contacts the emitter electrode (2), - a first trench gate electrode (3), which is arranged lateral to the base layer (5) and which is separated from the base layer (5), the first source region (7) and the drift layer (8) by a first insulating layer (31), wherein a channel is formable between the emitter electrode (2), the first source region (7), the base layer (5) and the drift layer (8), - a second insulating layer (32), which is arranged on top of the first trench gate electrode (3), - an enhancement layer (6), which separates the base layer (5) from the drift layer (8) at least in a plane parallel to the emitter side (11), - a grounded gate electrode (4) comprising a second, grounded trench gate electrode (41) and an electrically conducting layer (42), wherein the second trench gate electrode (41) is arranged lateral to the base layer (5) and which second trench gate electrode (41) is separated from the base layer (5), the enhancement layer (6) and the drift layer (8) by a third insulating layer (43), wherein the electrically conductive layer (42) covers and extends outside the second trench gate electrode (41) at least to a region above the base layer (5), wherein the electrically conductive layer (42) is separated from the base layer (5) by a fourth electrically insulating layer (44) and wherein the electrically conductive layer (42) contacts the second trench gate electrode (41), - a fifth insulating layer (45), which is arranged on top of the second trench gate electrode (41), which fifth insulating layer (45) has a recess (47) such that the electrically conducting layer (42) electrically contacts the emitter electrode (2).