IGBT Accumulation Layer Segmentation for On-Voltage and Turn-Off Loss Trade-off
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Solution Overview
Problem
Conventional insulated gate type bipolar transistors (IGBTs) with a single carrier storage layer exhibit high on-voltage due to excessive carrier storage, while those with multiple storage layers suffer from increased turn-off losses.
Innovation Solution
A semiconductor device design featuring a semiconductor substrate with multiple trench sections, a mesa section, and a drift layer, where the mesa section includes an emitter region, a contact region, and multiple accumulation layers with varying doping concentrations, optimizing the arrangement and depth distribution of these layers to balance on-voltage and turn-off losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single carrier storage layer is used in the IGBT, then the device structure is simpler, but the on-voltage becomes higher due to excessive carrier storage
Solution Approach 1:
The single carrier storage layer is divided into multiple accumulation layers (first accumulation layer, second accumulation layer, third accumulation layer) with different doping concentrations and depths. This segmentation allows each layer to contribute differently to carrier storage, reducing excessive carrier accumulation and lowering on-voltage while maintaining structural organization.
Solution Approach 2:
Each accumulation layer is assigned different local properties: the first accumulation layer has higher doping concentration and is positioned deeper, while the second and third accumulation layers have lower doping concentrations and are positioned shallower. This local differentiation optimizes carrier distribution, reducing overall carrier storage excess and lowering on-voltage.
2Quantity of substance
If multiple accumulation layers are provided below the contact region, then carrier storage is enhanced, but carrier discharge efficiency decreases leading to increased turn-off loss
Solution Approach 1:
The carrier storage function is segmented across multiple layers with different characteristics. The first accumulation layer (deeper, higher doping) provides stable carrier storage, while the second and third accumulation layers (shallower, lower doping) facilitate easier carrier extraction. This segmentation enables both adequate carrier storage and efficient discharge, reducing turn-off loss.
Solution Approach 2:
Instead of making all accumulation layers uniform to maximize storage, the invention inverts the approach by creating layers with decreasing doping concentrations from deeper to shallower positions. This inverted gradient structure naturally facilitates carrier discharge from shallower layers while maintaining storage capacity in deeper layers, improving turn-off efficiency.
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 design reduces on-voltage and turn-off losses by enhancing carrier injection and efficient carrier discharge, achieving a trade-off between these two critical performance metrics.
Implementation Method 1
The multiple accumulation layers may be provided side by side below the emitter region and the contact region in a depth direction of the semiconductor substrate. Each of the multiple accumulation layers may have a doping concentration of the first conductivity type higher than the doping concentration of the first conductivity type of the drift layer.
Data Source
AI summary
A semiconductor device having a semiconductor substrate is provided, the semiconductor substrate including: two trench sections extending in a predetermined direction; a mesa section provided between the two trench sections; and a drift layer, the mesa section including: an emitter region; a contact region; and multiple accumulation layers provided side by side in a depth direction below the emitter region and the contact region, and at least one accumulation layer among the multiple accumulation layers provided below at least a part of the emitter region, but not provided below a partial region of the contact region.