RC-IGBT Pilot Region Design for Snap-back Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Prior art reverse-conducting insulated gate bipolar transistors (RC-IGBTs) experience snap-back effects and increased turn-off losses due to uneven carrier distribution, leading to reduced maximum turn-off capability and reliability, especially at lower temperatures and currents.
Innovation Solution
The design incorporates a larger p-doped pilot region surrounded by first and second regions, with specific geometrical rules to optimize the IGBT area and reduce snap-back effects, ensuring equalized carrier distribution and improved thermal performance without increasing the pilot-IGBT size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a larger pilot region is introduced to eliminate snap-back effects, then reliability is improved, but device area increases
Solution Approach 1:
The patent applies local quality by creating distinct regions with different doping characteristics within the semiconductor device. Specifically, it introduces a lightly-doped pilot region (with doping concentration of 1e16 to 1e18 atoms/cm³) surrounded by heavily-doped shorted regions (with doping concentration of 1e19 to 1e21 atoms/cm³). This local differentiation allows the pilot region to eliminate snap-back effects while the surrounding shorted regions maintain compact dimensions, thus resolving the contradiction between reliability improvement and device area increase.
2Stress or pressure
If the base layer thickness is increased to handle higher voltages, then voltage handling capability is improved, but turn-off losses increase due to larger voltage drop
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration parameter in the base layer. It introduces a lightly-doped pilot region with doping concentration of 1e16 to 1e18 atoms/cm³, which is lower than the conventional base layer doping. This parameter change reduces the voltage drop across the base layer during turn-off, thereby reducing turn-off losses while maintaining adequate voltage handling capability through the carefully controlled doping level.
3Ease of manufacture
If pilot regions are distributed smaller across the device, then manufacturing is easier, but thermal performance and snap-back improvement are reduced
Solution Approach 1:
The patent applies segmentation by dividing the device into distinct functional zones: a central pilot region and surrounding shorted regions. Rather than distributing many small pilot regions throughout the device, it segments the structure into one (or a few) well-defined pilot region(s) with specific dimensions and doping characteristics. This segmented approach maintains manufacturing simplicity while achieving superior thermal performance and snap-back elimination compared to distributed smaller pilot regions.
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 approach enhances switching performance by minimizing dynamic avalanche during turn-off, improving maximum turn-off capability and reliability, while maintaining device performance in diode mode and extending the reverse bias safe operating area.
Implementation Method 1
leading to reduced snap-back effects, ensuring equalized carrier distribution and improved thermal performance
Implementation Method 2
enhances switching performance by minimizing dynamic avalanche during turn-off
Implementation Method 3
The snap-back effect of a BIGT depends on the resistance of the base layer, which in turn depends on the resistivity and thickness of the base layer 102. For devices having a greater base layer thickness 102, the voltage drop across the base layer is larger.
Implementation Method 4
The snap-back effect of a BIGT depends on the resistance of the base layer, which in turn depends on the resistivity and thickness of the base layer 102
Implementation Method 5
An n doped cathode layer 1 of higher doping concentration than the first doping concentration and a p doped anode layer 2 are alternately arranged on the collector side 103
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
A reverse-conducting semiconductor device (200) with an electrically active region in a central part of the device is provided, which comprises a freewheeling diode and an insulated gate bipolar transistor on a common wafer (100). Part of the wafer (100) forms a base layer (101) with a base layer thickness (102). A cathode layer (1) of a first conductivity type with at least one first region (10) and a anode layer (2) of a second conductivity type with at least one second and pilot region (20, 22) are alternately arranged on the collector side (103). Each region has a region area with a region width (11, 21, 23) surrounded by a region border. The RC-IGBT is designed in such a way that the following geometrical rules are fulfilled: each pilot region area is an area having a pilot region width of at least two times the base layer thickness (102); the at least one pilot region (22) is arranged in the central part of the active region in such a way that the mixed region laterally surrounds the at least one pilot region (22); the at least one second region is that part of the anode layer (2), which is not the at least one pilot region (22); the mixed region has a width of at least once the base layer thickness (102); the total area (i.e. sum of the areas) of the at least one pilot region (22) is between 10 and 45 % of the mixed region area; each first region width (11) is smaller than the base layer thickness (102); in each area on the emitter side (104), which lies in projection to one of the at least one pilot region (22), the plurality of source regions (3) have a first area density (31); in each area on the emitter side (104), which lies in projection to the mixed region, the plurality of source regions (3) have a second area density (32); and the first area density (31) is lower than the second area density (32).