Bipolar Semiconductor Device Collector Shorting via Conductive Layer
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Solution Overview
Problem
Existing methods for manufacturing reverse conducting bipolar semiconductor devices are complex, especially for thin wafer processing, and require deep or shallow diffused alternating P+ and N+ regions, which complicates the creation of electrically shorted collector regions.
Innovation Solution
A novel method involving a semiconductor substrate with a two-layer structure, where a highly conductive third layer is applied on the second main side, and a fourth layer of a second conductivity type is added between the third layer and the second electrical contact, eliminating the need for thick, highly doped regions and enabling efficient collector shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep or shallow diffused alternating P+ and N+ regions are used to create electrically shorted collector regions, then the reverse conducting capability is enabled, but the manufacturing process becomes complex especially for thin wafer processing
Solution Approach 1:
The patent changes the doping concentration parameter by using a second layer with higher doping concentration than the base layer, and introduces a highly conductive third layer (metal or graphene) to replace the complex alternating P+ and N+ region structure. This parameter change simplifies the manufacturing process while maintaining the reverse conducting capability through the highly conductive layer that enables electrical shorting of the collector regions.
Solution Approach 2:
The patent employs composite materials by combining the semiconductor substrate with a highly conductive material (metal or graphene) as the third layer. This composite structure replaces the complex doped region architecture with a simpler hybrid material system that achieves the same electrical shorting function with reduced manufacturing complexity.
2Reliability
If thick substrate is used to accommodate the complex doped region structure, then the alternating P+ and N+ regions can be formed, but the device thickness is increased which is not suitable for low voltage applications
Solution Approach 1:
The patent changes the structural parameters by introducing a thin highly conductive third layer instead of thick doped regions, and uses a second layer with optimized doping concentration to achieve the collector shorting function in a thin device structure suitable for low voltage applications below 2000 V.
3Reliability
If alternating P+ and N+ regions are implemented, then the PN junction shorting is achieved, but additional hole injection occurs during reverse recovery causing current overshooting
Solution Approach 1:
The patent changes the material parameter by introducing a highly conductive third layer (metal or graphene) that provides a different conduction mechanism, reducing additional hole injection during reverse recovery and minimizing current overshooting while maintaining PN junction shorting functionality.
Data Source
AI summary
A bipolar semiconductor device includes at least a four-layer structure, a first main side with a first electrical contact, and a second main side with a second electrical contact separated from the first main side by at least a base layer of first conductivity type. A shorting layer of the first conductivity type is arranged on the second main side of the base layer. A third layer includes a patterned highly conductive material, such as metal and/or silicides, graphene, etc., and is deposited on the shorting. A fourth layer of the second conductivity type is arranged directly on the third layer, inserted between the shorting layer and the second electrical contact. This concept can be applied to any non-punch-through or punch-through reverse conducting IGBT designs, but is particularly effective for devices using thin wafers, and is also applicable to bipolar diodes in order to improve a soft recovery process.