IGBT Cell Structure With Control Gate for Lower Turn-Off Loss
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Solution Overview
Problem
Existing insulated gate bipolar transistors (IGBTs) face challenges in optimizing the trade-off between on-state voltage drop, turn-off loss, reliability, and cost, particularly in reducing switch loss and switch frequency, due to the lack of an effective carrier storage layer which prolongs turn-off time.
Innovation Solution
A cell structure for IGBTs is introduced, featuring a control gate and a carrier storage layer with a specific arrangement of gate trench bodies, dielectric layers, and ion implantation technology to form an N-type storage layer, allowing for improved carrier extraction and reduced turn-off time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a carrier storage layer is introduced to optimize on-state voltage drop and turn-off loss, then the trade-off relationship between on-state voltage drop and turn-off loss is improved, but the turn-off time is prolonged due to lack of effective carrier extraction channel
Solution Approach 1:
The patent divides the gate structure into two separate gate trenches: a control gate trench and a driver gate trench. This segmentation allows independent control of carrier storage and carrier extraction functions. The control gate trench contains the carrier storage layer while the driver gate trench provides the extraction channel, resolving the contradiction between storing carriers (to reduce turn-off loss) and extracting carriers (to reduce turn-off time).
Solution Approach 2:
The patent introduces an intermediary structure - the driver gate trench - that acts as a mediator between the control gate and the channel. This driver gate trench specifically provides the minority carrier extraction channel without interfering with the carrier storage function of the control gate trench, enabling simultaneous optimization of turn-off loss and turn-off time.
2Manufacturing precision
If the carrier storage layer width is equal to the distance between two adjacent trench gates, then the threshold voltage uniformity is optimized, but the minority carrier extraction channel cannot be generated when device is turned off
Solution Approach 1:
The patent segments the gate function by creating two distinct gate trenches with different purposes. The control gate trench maintains the carrier storage layer for threshold voltage uniformity, while the driver gate trench is specifically designed to provide the minority carrier extraction channel. This segmentation allows both requirements to be satisfied simultaneously without compromising either threshold voltage uniformity or carrier extraction capability.
Solution Approach 2:
The patent applies local quality by giving different regions of the gate structure different functions. The control gate trench region is optimized for carrier storage and threshold voltage control, while the driver gate trench region is optimized for carrier extraction. This localized functional differentiation resolves the contradiction between maintaining uniform threshold voltage and enabling effective carrier extraction.
3Ease of operation
If two kinds of gates are implanted between sides of two kinds of gates to provide gate signals, then the control capability is enhanced, but the device complexity increases
Solution Approach 1:
The patent segments the control function into two separate gate structures with distinct responsibilities. The control gate handles carrier storage and general device control, while the driver gate specifically handles minority carrier extraction. This functional segmentation enhances control capability by providing independent control paths while keeping each gate's function simple and well-defined, thus managing device complexity through functional specialization rather than adding complex interaction mechanisms.
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
The proposed structure achieves lower turn-off loss and shorter turn-on and turn-off delays with an on-state voltage drop comparable to conventional carrier storage layer structures, enhancing the trade-off relationship between on-state voltage drop and turn-off loss.
Implementation Method 1
a carrier storage layer with a specific arrangement of gate trench bodies, dielectric layers, and ion implantation technology to form an N-type storage layer, allowing for improved carrier extraction and reduced turn-off time
Implementation Method 2
ion implantation technology to form an N-type storage layer
Data Source
AI summary
A cell structure of an insulated gate bipolar transistor (IGBT) with a control gate and a carrier storage layer, is provided including: an N-type drift layer with a first surface, an active region on a second surface opposing the first and an N-type storage layer, a P-type body layer and an N-type doped layer sequentially stacked in the active region from the first to the second surface, gate trench bodies, each of which extends from the second to the first surface in a first direction perpendicular to the first surface and contacts the N-type drift layer, and each of the at least three gate trench bodies is a gate trench or a control gate trench. A sidewall of the gate trench is in contact with the active region, and a sidewall of the control gate trench is in contact with the P-type layer but not with the N-type layer.