Reverse Conducting Power Semiconductor Device With Segmented Cathode
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Solution Overview
Problem
Reverse conducting power semiconductor devices face challenges in achieving uniform turn-on and turn-off, maximum controllable current, and low on-state voltage, leading to inefficiencies and potential overheating.
Innovation Solution
The design includes specific outer cathode layer regions near diode cells, optimized plasma distribution, and an interdigitated arrangement of gate commutated thyristor and diode cells to enhance current controllability and reduce conduction losses, with the width of outer cathode layers ranging from 20% to 75% of intermediate layers, and a ratio of diode cells to cathode layers between 1:3 to 1:5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single freewheeling diode part is used in RC-IGCT design, then device complexity is reduced, but thermal resistance increases due to concentrated heat in one area
Solution Approach 1:
The diode function is segmented into multiple distributed diode cells (12) alternating with GCT cells (2) across the wafer. This segmentation distributes the heat generation across multiple locations rather than concentrating it in a single diode area, thereby reducing thermal resistance while maintaining the reverse conducting function.
Solution Approach 2:
The GCT cells (2) and diode cells (12) are merged into a single integrated wafer (1) with alternating arrangement. This merging allows heat from GCT cells to spread into diode cell regions and vice versa, improving thermal management while maintaining electrical functionality of both device types.
2Power
If outer cathode layer regions are made wider to improve current handling, then maximum controllable current increases, but on-state voltage increases leading to higher conduction losses
Solution Approach 1:
The cathode layer structure is designed with varying local qualities: outer cathode layer regions (34b) have different widths (20%-75% of intermediate layers) compared to intermediate regions (34a). This local variation optimizes plasma distribution and current handling in different areas, allowing high maximum controllable current while minimizing on-state voltage and conduction losses.
3Loss of energy
If plasma distribution is improved for lower on-state voltage, then conduction losses decrease, but uniformity of turn-on and turn-off becomes more challenging
Solution Approach 1:
The cathode layer is segmented into multiple regions (outer regions 34b and intermediate regions 34a) with different width characteristics. This segmentation creates optimized plasma distribution patterns that simultaneously achieve low on-state voltage and uniform plasma extraction during turn-off, resolving the contradiction between energy loss and switching uniformity.
Solution Approach 2:
The width parameter of cathode layer regions is changed systematically: outer regions (34b) have widths of 20%-75% of intermediate regions (34a). This parameter variation optimizes both plasma distribution for low conduction losses and plasma extraction uniformity for reliable turn-off, achieving both goals simultaneously.
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 configuration increases maximum controllable current by up to 27% and reduces conduction losses by 4.5% compared to existing BGCT designs, ensuring uniform plasma extraction and improved current handling while maintaining efficient heat distribution.
Implementation Method 1
optimized plasma distribution
Implementation Method 2
uniform plasma extraction from the gate electrodes
Implementation Method 3
heat is distributed more uniformly in the wafer
Data Source
Figure 1
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AI summary
A reverse-conducting power semiconductor is provided. It comprises a plurality of diode cells (312) and a plurality of gate commutated thyristor (GCT) cells (32). Each GCT cell (32) comprises first cathode layer (34), wherein the first cathode layer (34) of each GCT cell (32) includes at least three cathode layer regions (34a, 34b), which are separated from each other by a base layer (35), wherein in orthogonal projection onto a plane parallel to the first main side (41) each one of the cathode layer regions (34a, 34b) is strip-shaped with a length in a direction along a longitudinal axis thereof and a width (w, w') in a direction vertical to the longitudinal axis, wherein the diode cells (312) alternate with the GCT cells (32) in a lateral direction in at least a mixed part, wherein in each GCT cell (32), the width (w') of each one of the two outer cathode layer regions (34b) next to a diode cell (312) neighbouring to that GCT cell (32) is less than the width (w) of any intermediate cathode layer region (34a) between the two outer cathode layer regions (34b) in that GCT cell (32).