Reverse-conducting Semiconductor Device with Segmented Diode and IGCT Cells
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Solution Overview
Problem
Existing reverse-conducting semiconductor devices face overheating issues due to heat concentration in single diode or IGCT parts, leading to large device sizes and inefficient thermal management, as well as poor electrical performance with snappy reverse recovery and limited current handling capabilities.
Innovation Solution
A reverse conducting power semiconductor device with alternating arrangements of IGCT and diode cells, forming a bipolar junction transistor (BJT) for improved turn-off performance and reduced gate power, along with distributed cell structures for enhanced thermal resistance and current handling by allowing heat to spread across a larger area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single free-wheeling diode is integrated on the same wafer with IGCT cells, then device integration is achieved, but heat concentration occurs leading to overheating problems
Solution Approach 1:
The device is segmented into multiple diode cells (first diode cell and second diode cell) that are laterally separated from each other and from the IGCT part. This segmentation distributes the heat generation across multiple spatial locations, preventing heat concentration in a single location while maintaining integration on the same wafer.
2Device complexity
If a single free-wheeling diode is integrated on the same wafer with IGCT cells, then device integration is achieved, but device size increases due to strict dedication for diode or IGCT mode
Solution Approach 1:
The first and second diode cells serve dual purposes: they function as free-wheeling diodes during IGCT operation and can be activated to conduct current during IGCT cell defects. This multi-functionality allows the device to maintain compact integration without requiring separate dedicated areas for different operational modes.
Solution Approach 2:
The device utilizes conductivity modulation in the drift layer to dynamically change its electrical parameters. During normal operation, the drift layer has high resistance to block reverse current. During defects, the drift layer becomes conductive to allow current flow through the diode cells, enabling adaptive functionality without increasing physical device size.
3Adaptability or versatility
If IGCT cells and diode are completely separated with no interaction, then functional independence is achieved, but thermal management efficiency deteriorates
Solution Approach 1:
The device structure is segmented into functionally independent IGCT cells and diode cells with lateral separation, maintaining functional independence. However, the segments are positioned in close proximity and share common structural elements (drift layer, buffer layer, substrate), enabling efficient thermal coupling for improved thermal management.
Solution Approach 2:
The IGCT cells and diode cells are merged into a single integrated device structure on the same wafer, sharing common layers (drift layer, buffer layer, substrate). This merging provides thermal coupling that improves heat dissipation while maintaining functional independence through lateral separation and selective activation.
4Ease of manufacture
If a single free-wheeling diode is arranged in the central part or at the circumference, then manufacturing simplicity is maintained, but current handling capability is limited
Solution Approach 1:
The single diode is segmented into multiple diode cells (first diode cell and second diode cell) that are distributed laterally across the wafer. This segmentation increases the total current handling capability by providing multiple parallel current paths while maintaining manufacturing simplicity through a systematic arrangement that can be processed using standard fabrication techniques.
Data Source
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Figure 5~6
AI summary
A reverse-conducting power semiconductor device (1) with a wafer (10) having a first main side (11) and a second main side (15), which is arranged parallel to the first main side (11), is provided. The device comprises a plurality of diode cells (96) and a plurality of IGCT cells (91), wherein each IGCT cell comprises layers in the following order between the first and second main side (11, 15): - a cathode electrode (2), - a first cathode layer (4) of the first conductivity type, - a base layer (6) of the second conductivity type, - a drift layer (3) of the first conductivity type, - a buffer layer (8) of the first conductivity type, - a first anode layer (5) of the second conductivity type, and - a first anode electrode (25). Each IGCT cell (91) further comprises a gate electrode (7), which is arranged lateral to the first cathode layer (4) and separated from it by the base layer (6). Each diode cell (96) comprises a second anode electrode (28) on the first main side (11), which is in contact to a second anode layer (55) of the second conductivity type, which second anode layer (55) is separated from the base layer (6) by the drift layer (3), and a second cathode layer (45) of the first conductivity type on the second main side (15), which is arranged alternating to the first anode layer (5). The device comprises at least one mixed part (99), in which the second anode layers (55) of the diode cells (96) alternate with the first cathode layers (4) of the IGCT cells (91).