IGBT Cell Structure With Control Gate for Faster Carrier Extraction
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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 and dielectric layers, where the control gate signal is applied ahead of the main gate signal to enhance carrier storage and extraction, and the carrier storage layer is formed using ion implantation technology to improve turn-off efficiency.
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 between Vcesat and Eoff is improved, but the switch frequency and switch loss remain limited due to prolonged turn-off time
Solution Approach 1:
The gate structure is segmented into a conventional gate and an additional control gate. The control gate is positioned to contact the P-type body layer without contacting the N-type storage layer, enabling independent control of carrier extraction. This segmentation allows the control gate to accelerate minority carrier extraction from the storage layer, reducing turn-off time while maintaining the carrier storage function for low on-state voltage drop.
Solution Approach 2:
The control gate acts as an intermediary element between the conventional gate and the N-type storage layer. By positioning the control gate to contact only the P-type body layer, it mediates the extraction process by creating an electric field that accelerates minority carrier removal from the storage layer, thereby reducing turn-off time without compromising the carrier storage function.
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 a minority carrier extraction channel cannot be generated when the device is turned off
Solution Approach 1:
The gate system is divided into a conventional gate for maintaining threshold voltage uniformity and a separate control gate for enabling carrier extraction. The control gate's sidewall contacts the P-type body layer to create an extraction channel, while the conventional gate maintains the carrier storage layer width for uniform threshold voltage. This segmentation resolves the contradiction between uniformity and extraction capability.
Solution Approach 2:
The control gate extends in a different spatial dimension compared to the conventional gate structure. By positioning the control gate to contact the P-type body layer at a different location, it creates a vertical extraction channel that does not interfere with the horizontal carrier storage function, enabling both uniformity and extraction capability.
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 losses and shorter turn-on and turn-off delays with an on-state voltage drop comparable to conventional carrier storage layer structures, while maintaining comparable on-state voltage drop, thereby improving the trade-off relationship between these parameters.
Implementation Method 1
the carrier storage layer is formed using ion implantation technology to improve turn-off efficiency
Data Source
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Figure 3A~3B
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AI summary
The present invention provides a cell structure of an insulated gate bipolar transistor (IGBT) with a control gate and a carrier storage layer, including: an N-type drift layer with a first surface, an active region on a second surface opposing the first surface and including 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 surface to the second surface, at least three gate trench bodies, each of the at least three gate trench bodies extends from the second surface 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 body layer but not in contact with the N-type storage layer.