Bipolar Punch-Through Device Soft Turn-Off via Segmented Buffer
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Solution Overview
Problem
Existing bipolar punch-through semiconductor devices are susceptible to on-state snap-back effects and lack effective control over electrical properties, especially under extreme switching conditions, due to low punch-through voltage values and sensitivity to temperature and current variations.
Innovation Solution
A bipolar punch-through semiconductor device with a semiconductor substrate featuring a two-layer structure, including a base layer and a buffer layer with alternately arranged shallow and highly doped P+ and N+ regions, allowing for controlled hole injection and soft turn-off switching through Turn-off Charge Induction (TCI) mechanism, independent of conventional design rules for increasing punch-through voltage or anode injection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thicker and/or lower resistivity base regions are chosen to increase punch-through voltage, then device softness is improved, but device losses increase and cosmic ray failure rates increase
Solution Approach 1:
The base region is segmented into multiple zones with different doping concentrations (first base region with lower doping, second base region with higher doping). This segmentation allows the device to achieve soft turn-off characteristics through the lower-doped region while the higher-doped region maintains lower losses and improved cosmic ray immunity, resolving the contradiction between softness and losses.
2Reliability
If deep and low doped buffer profiles are introduced to store charge, then device softness is improved, but the effect is limited under extreme switching conditions
Solution Approach 1:
Different regions of the buffer are assigned different doping concentrations to perform different functions. The first buffer region has lower doping to store charge for softness, while the second buffer region has higher doping to provide robust performance under extreme switching conditions. This local differentiation resolves the contradiction between softness and adaptability.
3Reliability
If anode injection efficiency is increased to provide additional excess carriers, then device softness is improved, but turn-off losses increase and device usage is limited to low frequency applications
Solution Approach 1:
The invention changes the doping concentration parameter in the base and buffer regions to achieve soft turn-off characteristics without relying on increased anode injection efficiency. By using a multi-zone structure with optimized doping profiles, the device achieves softness while maintaining fast switching capability for high-frequency applications, resolving the contradiction between softness and productivity.
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
The device exhibits reduced snappy behavior and improved control over electrical properties, with smoother voltage and current profiles during turn-off and reverse recovery, reducing the risk of device failure and enabling broader design freedom for lower loss and more robust power semiconductor devices.
Implementation Method 1
The operating mechanism of this technology is based on the returning electrons during diode reverse recovery which will flow near the P+N junctions towards the N+ cathode regions. This results in an increased lateral voltage drop at the P+N junctions which will exceed the built-in voltage of the P+N junction, hence causing hole injection from the P+ region.
Implementation Method 2
the particles of the second conductivity type are activated at such conditions that the particles diffuse into the substrate by not more than 2 μm
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A bipolar punch-through semiconductor device with a semiconductor substrate (1), which comprises at least a two-layer structure, one of the layers being a base layer (10) of the first conductivity type, is provided. The substrate comprises a first main side (11) with a first electrical contact (2) and a second main side (12) with a second electrical contact (3). A buffer layer (4) of the first conductivity type is arranged on the base layer (10). A first layer (5), which comprises alternately first regions (51, 51') of the first conductivity type and second regions (52, 52') of the second conductivity type, is arranged between the buffer layer (4) and the second electrical contact (3). The second regions (52, 52') are activated regions with a depth of at maximum 2 μm and a junction profile, which drops from 90 % to 10 % of the maximum doping concentration within at most 1 μm.