IGBT Boost Structure for High Current Robustness
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Solution Overview
Problem
IGBTs face a trade-off between high critical saturation current for robustness against high currents and low switching and leakage losses, as increasing doping concentration in the second emitter region leads to increased reverse recovery losses and leakage currents.
Innovation Solution
Incorporating a boost structure with a base region of the first doping type and an auxiliary emitter region of the second doping type, separated by a pass region, which allows for higher dopant doses in the drift and field-stop regions, and a specific doping profile that stops the electric field in the field-stop region when a critical field strength is reached, thereby managing charge carrier plasma and electric field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the doping concentration of the second emitter region is increased to increase the critical saturation current, then the robustness against high currents is improved, but the reverse recovery losses and leakage currents increase
Solution Approach 1:
The invention divides the emitter structure into two separate regions: the original second emitter region and a newly introduced auxiliary emitter region. This segmentation allows the original second emitter region to maintain lower doping concentration (reducing reverse recovery losses) while the auxiliary emitter region provides additional current-carrying capacity (maintaining robustness against high currents). The auxiliary emitter region is separated from the second emitter region by a base region, creating independent functional zones that can be optimized separately.
Solution Approach 2:
The invention applies different doping concentrations to different regions: the auxiliary emitter region has a first doping concentration, the base region has a second doping concentration, and the second emitter region has a third doping concentration. This local differentiation allows each region to be optimized for its specific function - the auxiliary emitter for high current capacity, the base for charge carrier management, and the second emitter for controlled injection - thereby resolving the contradiction between overall robustness and localized losses.
2Reliability
If the doping concentration of the second emitter region is increased to increase the critical saturation current, then the robustness against high currents is improved, but the leakage currents in off-state increase
Solution Approach 1:
By segmenting the emitter structure into auxiliary emitter region, base region, and second emitter region, the invention creates distinct functional zones. The base region acts as a buffer that prevents direct interaction between the high-doped auxiliary emitter and the drift region, thereby suppressing leakage current paths while still allowing the auxiliary emitter to contribute to high-current capability when properly activated.
Solution Approach 2:
The base region serves as an intermediary between the auxiliary emitter region and the drift region. It mediates the charge carrier flow, allowing controlled injection during high-current operation while blocking unwanted leakage paths during off-state. This intermediary structure enables the system to achieve high current robustness without proportionally increasing leakage currents.
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 design enhances the IGBT's robustness against high currents without increasing switching and leakage losses, allowing for efficient operation in both on-state and off-state conditions by independently adjusting turn-off losses and high-current capabilities.
Implementation Method 1
the first emitter region injects first type charge carriers via the conducting channel into the drift region and the second emitter region injects second type charge carriers into the drift region where the first type charge carriers and the second type charge carriers form a charge carrier plasma
Implementation Method 2
A doping profile of the drift region and the field-stop region is such that in the off-state of the transistor device an electric field associated with applying a load path voltage between the first emitter region and the second emitter region stops in the field-stop region spaced apart from the at least one auxiliary emitter region when a critical field strength is reached at a pn junction between the body region and the drift region
Implementation Method 3
A gate electrode is dielectrically insulated from the body region by a gate dielectric, and serves to control a conducting channel in the body region
Data Source
AI summary
A transistor device includes a first emitter region of a first doping type, a second emitter region of a second doping type, a body of the second doping type, a drift region of the first doping type, a field-stop region of the first doping type, at least one boost structure, and a gate electrode. The boost structure is arranged between the field-stop region and the second emitter region. The at least one boost structure includes a base region of the first doping type and at least one auxiliary emitter region of the second doping type separated from the second emitter region by the base region. An overall dopant dose in the drift region and the field-stop region in a current flow direction of the transistor device is higher than a breakthrough charge of a semiconductor material of the drift region and the field-stop region.