Lateral IGBT Segmented Junctions for On-Resistance and Switching Speed
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Solution Overview
Problem
Lateral Insulated-Gate Bipolar Transistors (LIGBTs) face challenges in achieving a balance between on-resistance and turning-off time due to residual minority carrier holes, leading to higher power consumption and longer switching times.
Innovation Solution
The LIGBT design incorporates P+ shallow junctions and an N+ shallow junction between the anode and cathode terminals, allowing for efficient hole injection and quick extraction of minority carriers when turned on and off, respectively, by forming multiple injection paths and a low-resistance extraction path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If LIGBT uses conventional structure with P well and N-region, then on-resistance is reduced by carrier injection, but turning-off time increases due to residual minority carrier holes
Solution Approach 1:
The P well is divided into multiple P+ shallow junctions (first, second, and third P+ shallow junctions) at different depths and positions. This segmentation creates multiple independent hole injection paths, allowing efficient on-resistance reduction while enabling selective extraction of minority carriers for faster turn-off through the specifically positioned third P+ shallow junction near the drift region.
Solution Approach 2:
Different P+ shallow junctions are positioned at different locations and depths within the P well to perform different functions: the first and second P+ shallow junctions provide general hole injection, while the third P+ shallow junction is specifically positioned near the drift region to facilitate rapid minority carrier extraction during turn-off, creating local quality variations that optimize both on-resistance and turn-off time.
2Reliability
If LIGBT increases hole concentration to reduce on-resistance, then conductivity improves, but power consumption increases due to residual minority carriers
Solution Approach 1:
The segmented P+ shallow junctions create multiple injection paths that optimize hole distribution. The third P+ shallow junction positioned near the drift region enables efficient minority carrier extraction, reducing residual holes and associated power consumption while maintaining the conductive modulation effect through coordinated operation of all P+ shallow junctions during on-state.
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 design reduces on-resistance and enhances switching speed by enabling efficient hole injection and rapid extraction of minority carriers, thereby minimizing power consumption and turning-off time losses.
Implementation Method 1
an efficient injection of holes can be achieved and the on-resistance can be reduced by a longitudinal injection of the P+ shallow junctions and the P well and a lateral injection of the P+ shallow junctions
Implementation Method 2
a path quickly extracting minority carrier (holes) is formed by the N-type buffer region, the N-region and the N+ shallow junctions, which achieves a quick turning-off and reduces a turning-off state loss
Data Source
Figure 1~2
AI summary
A lateral insulated gate bipolar transistor comprises a substrate (10); an anode terminal located on the substrate, comprising: an N-type buffer region (51) located on the substrate (10); a P well (53) located in the N-type buffer region; an N-region (55) located in the P well (53); two P+ shallow junctions (57) located on a surface of the P well (53); and an N+ shallow junction (59) located between the two P+ shallow junctions (57); a cathode terminal located on the substrate; a draft region (30) between the anode terminal and cathode terminal; and a gate (62) between the anode terminal and cathode terminal.