IGBT Drift Zone Segmentation for Reverse Recovery Charge Reduction
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Solution Overview
Problem
The integration of a freewheeling diode with Insulated-Gate Bipolar Transistors (IGBTs) leads to electrical losses due to Reverse Recovery Charge (RRC), which increases power dissipation and reduces IGBT lifetime, especially in applications with high temperature and power conditions.
Innovation Solution
A reduced charge-carrier lifetime region is formed in the drift zone of the IGBT by irradiating the semiconductor substrate to create an end-of-range irradiation region with vacancies, which reduces the RRC of the freewheeling diode, and metal atoms are diffused into these vacancies to enhance the region's effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single reduced charge-carrier lifetime region is formed by irradiating the drift zone, then diode RRC is reduced, but VCESat increases and leakage current increases
Solution Approach 1:
The patent divides the drift zone into multiple irradiated regions with different charge carrier lifetimes rather than using a single uniformly irradiated region. This segmentation allows different portions of the drift zone to have optimized characteristics, reducing overall RRC while maintaining acceptable VCESat and leakage current levels.
Solution Approach 2:
The patent applies local quality by creating regions with different irradiation doses or types within the drift zone, resulting in spatially varying charge carrier lifetimes. This allows specific areas to be optimized for RRC reduction while other areas maintain characteristics that limit leakage current and VCESat increases.
2Loss of energy
If the doping concentration of the highly doped emitter contact region is lowered to reduce diode RRC, then RRC decreases, but latch-up robustness significantly reduces
Solution Approach 1:
The patent extracts the RRC reduction function from the emitter contact region by implementing irradiated regions in the drift zone instead. This separates the RRC control mechanism from the emitter doping, allowing RRC reduction without compromising the emitter's latch-up robustness.
Solution Approach 2:
The patent introduces irradiated regions in the drift zone as an intermediary mechanism to reduce RRC. This intermediary approach achieves RRC reduction without directly modifying the emitter contact region, thereby preserving latch-up robustness while still achieving the desired RRC reduction.
3Loss of energy
If a very low charge carrier lifetime region is formed in the drift zone to reduce diode RRC, then diode RRC decreases, but VCESat increases
Solution Approach 1:
The patent segments the drift zone into multiple irradiated regions rather than creating a single very low charge carrier lifetime region. This segmentation distributes the RRC reduction effect across multiple zones, achieving overall RRC reduction while preventing excessive VCESat increase that would result from a uniformly very low lifetime region.
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 approach decreases the Reverse Recovery Charge of the freewheeling diode, reducing electrical losses and improving IGBT performance by minimizing stored charge and leakage current while maintaining emitter efficiency.
Implementation Method 1
A reduced charge-carrier lifetime region is formed in the drift zone of the IGBT by irradiating the semiconductor substrate to create an end-of-range irradiation region with vacancies
Implementation Method 2
metal atoms are diffused into these vacancies to enhance the region's effectiveness
Data Source
AI summary
A method of manufacturing a reduced free-charge carrier lifetime semiconductor structure includes forming a plurality of transistor gate structures in trenches arranged in a semiconductor substrate, forming a body region between adjacent ones of the transistor gate structures and forming an end-of-range irradiation region between adjacent ones of the transistor gate structures, the end-of-range irradiation region having a plurality of vacancies.