IGBT Lifetime Control Regions for Leakage Current
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Solution Overview
Problem
Conventional semiconductor devices face challenges in improving leakage current characteristics and achieving a favorable trade-off between ON-voltage and turn-off loss, particularly in the design of insulated gate bipolar transistors (IGBTs) where the existing structures do not effectively manage hole injection and carrier recombination.
Innovation Solution
The semiconductor device incorporates a unique structure with a semiconductor substrate featuring a first-conductivity type drift region, a transistor portion, and a diode portion, including trench portions, conductive portions, and lifetime control regions. Specifically, the device employs upper-surface and lower-surface side lifetime control regions with varying lifetime killer concentrations and arrangements to optimize carrier recombination and reduce leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional structures are used in IGBTs, then manufacturing is simpler, but leakage current characteristics deteriorate
Solution Approach 1:
The drift region is divided into multiple segments along the depth direction, with different conductivity types (first-conductivity type and second-conductivity type regions) arranged in sequence. This segmentation allows different portions to perform different functions: some segments suppress leakage current while others manage hole injection, thereby improving leakage current characteristics without requiring complete structural redesign
Solution Approach 2:
Different regions within the drift region are assigned different conductivity types and properties. Specifically, first-conductivity type drift regions and second-conductivity type drift regions are arranged alternately, creating local variations in electrical properties. This local quality differentiation enables targeted control of carrier behavior in specific areas, improving leakage current characteristics while maintaining overall device functionality
2Reliability
If lifetime killer concentration is increased, then leakage current is reduced, but ON-voltage increases
Solution Approach 1:
Lifetime killers are distributed non-uniformly throughout the drift region, with different concentrations in different segments. By placing lifetime killers selectively in certain first-conductivity type drift regions while maintaining lower concentrations in other regions, the patent achieves localized suppression of leakage current without uniformly increasing ON-voltage across the entire device
Solution Approach 2:
The drift region is segmented into multiple zones with different lifetime killer concentrations. Some segments have higher lifetime killer concentrations to suppress leakage current, while other segments have lower concentrations to maintain low ON-voltage. This segmented approach allows independent optimization of leakage current and ON-voltage characteristics in different regions
3Strength
If drift region thickness is increased, then breakdown voltage is improved, but turn-off loss increases
Solution Approach 1:
The drift region is divided into multiple thinner segments with alternating conductivity types, rather than using a single thick drift region. This segmentation achieves the required breakdown voltage through the cumulative effect of multiple segments while reducing the thickness of individual segments. The reduced individual segment thickness decreases carrier storage, thereby reducing turn-off loss while maintaining overall breakdown voltage strength
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 configuration enhances leakage current characteristics, suppresses hole injection, and achieves a better trade-off between ON-voltage and turn-off loss, improving the overall performance of the semiconductor device by effectively managing carrier dynamics.
Implementation Method 1
includes a lifetime killer... optimize carrier recombination and reduce leakage currents
Data Source
AI summary
To provide a semiconductor device, wherein each of a transistor portion and a diode portion that are arrayed along an array direction has: a second-conductivity type base region provided above a first-conductivity type drift region inside a semiconductor substrate; a plurality of trench portions that penetrate the base region from an upper surface of the semiconductor substrate, extend at the upper surface of the semiconductor substrate and in a direction of extension perpendicular to the array direction, and have conductive portions provided therein; and a lower-surface side lifetime control region that lies on a lower-surface side in the semiconductor substrate, and from the transistor portion to the diode portion, and includes a lifetime killer. In the array direction, the transistor portion may have a portion provided with the lower-surface side lifetime control region, and another portion not provided with the lower-surface side lifetime control region.