RC-IGBT Trench Structure for Lower Reverse Recovery Current
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Solution Overview
Problem
In reverse-conducting insulated gate bipolar transistors (RC-IGBTs), the operation of the IGBT and freewheeling diode can interfere, leading to increased reverse recovery current and switching loss due to incomplete discharge of holes from the IGBT region during diode turn-off.
Innovation Solution
The RC-IGBT design incorporates a resistance reduction region with a higher p-type impurity concentration between the base and emitter regions, and a trench contact portion that promotes hole discharge along the side surfaces, reducing the injection of holes into the diode region and enhancing latch-up immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the IGBT and freewheeling diode are formed in the same semiconductor chip, then chip size is reduced and heat generation locations are dispersed, but the operation of the IGBT and diode interfere with each other causing increased reverse recovery current and switching loss
Solution Approach 1:
The semiconductor device is divided into a transistor region containing the IGBT and a diode region containing the freewheeling diode, with each region independently structured and doped. This segmentation allows separate optimization of each device's characteristics while sharing the same chip substrate, reducing overall chip size while managing the interference between devices through spatial separation and distinct doping profiles.
Solution Approach 2:
Different doping concentrations and types are applied to different regions: the transistor region has a first doping concentration profile while the diode region has a second doping concentration profile. This local quality approach allows each region to be optimized for its specific function, with the diode region structured to minimize hole injection into the IGBT region during diode turn-off, thereby reducing switching loss while maintaining compact chip size.
2Reliability
If the diode is turned off, then the freewheeling function is completed, but holes injected from the IGBT region are not discharged causing increased reverse recovery current
Solution Approach 1:
The harmful effect of hole accumulation in the diode region is addressed by providing a dedicated hole discharge path through the collector region. The n-type collector region with its specific doping concentration serves to extract and discharge holes from the diode region to the substrate, removing the harmful accumulation of holes that would otherwise cause high reverse recovery current when the diode turns off.
Solution Approach 2:
The collector region acts as an intermediary between the diode region and the substrate, facilitating the discharge of holes from the diode region. This intermediate n-type region with controlled doping concentration provides a pathway for hole extraction, mediating the interaction between the diode operation and the substrate to minimize reverse recovery effects while maintaining reliable diode switching function.
Data Source
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AI summary
A semiconductor device of embodiments includes a transistor region and a diode region. The transistor region includes: a first conductive type first semiconductor region, a second conductive type second semiconductor region, a first conductive type third semiconductor region in this order in a semiconductor layer; a second conductive type fourth semiconductor region and a first conductive type fifth semiconductor region on the third semiconductor region and arranged alternately in a first direction; a first conductive type sixth semiconductor region between the third and the fourth semiconductor region a first trench spaced from the sixth semiconductor region; a gate electrode in the first trench; a first electrode having a first portion, a bottom surface of the first portion being in contact with the third semiconductor region and side surfaces of the first portion being in contact with the fourth, the fifth, and the sixth semiconductor regions; and a second electrode.