LIGBT Forward Conduction Unit With Shared PN-Schottky Diodes
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Solution Overview
Problem
Conventional power devices with lateral insulated gate bipolar transistors (LIGBTs) suffer from slower switching speed, higher power consumption, and lower power conversion efficiency due to the generation of significant reverse recovery charges (Qrr) from PN diodes.
Innovation Solution
Incorporating a Schottky diode in parallel with the PN diode, both sharing common regions and forming a staggered comb-teeth interface with a metal line that alternately contacts the N-type and P-type regions, to reduce unwanted reverse recovery charges and enhance switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a PN diode is used in the power device, then the device can provide forward conduction function, but the PN diode generates huge reverse recovery charges (Qrr) which causes slower switching speed, higher power consumption, and lower power conversion efficiency
Solution Approach 1:
The patent combines a PN diode and a Schottky diode into a single integrated forward conductive unit. The Schottky diode is formed alongside the PN diode structure, sharing common regions such as the N-type region and P-type well. This merging allows the device to leverage the low reverse recovery charge characteristic of Schottky diodes while maintaining the forward conduction capability of the PN diode, thereby reducing overall reverse recovery charges and improving switching speed without sacrificing forward conduction performance
2Speed
If a Schottky diode is added in parallel with the PN diode to reduce reverse recovery charges, then switching speed improves, but the device area increases
Solution Approach 1:
The patent merges the Schottky diode and PN diode into a shared structure where both diodes utilize common regions including the N-type region, P-type well, and field oxide region. The Schottky gate is formed over the field oxide region adjacent to the PN diode gate, and both diodes share the same N-type extension region and contact structures. This integrated design significantly reduces the total device area compared to implementing separate PN diode and Schottky diode structures
Solution Approach 2:
The forward conductive unit serves multiple functions simultaneously: the PN diode provides robust forward conduction, the Schottky diode provides low reverse recovery charge path, and together they form an integrated protective structure. The shared N-type region and P-type well serve both diodes, making the structure multi-functional and area-efficient
3Area of stationary object
If the PN diode and Schottky diode share common regions, then the device area is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent segments the device into distinct functional regions with clear boundaries: the PN diode region with its gate and contact structures, the Schottky diode region with its Schottky gate over the field oxide, and the shared regions including the N-type extension and P-type well. This segmentation approach, while creating a multi-region structure, uses systematic formation steps for each region that follow conventional semiconductor manufacturing processes, making the increased structural complexity manageable through organized process segmentation
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 reduces reverse recovery charges, improves switching speed, and decreases power consumption while maintaining performance without increasing the device area, effectively enhancing power conversion efficiency.
Implementation Method 1
a forward conductive unit, which is connected in parallel to the plurality of LIGBTs, wherein the forward conductive unit consists of a PN diode and a Schottky diode which are connected in parallel to each other
Implementation Method 2
the first N-type region and the first P-type well form a PN junction therebetween
Data Source
AI summary
A power device which is formed on a semiconductor substrate includes: plural lateral insulated gate bipolar transistors (LIGBTs) and a forward conductive unit. The plural LIGBTs are connected in parallel to each other. The forward conductive unit is connected in parallel to the plural LIGBTs. The forward conductive unit consists of a PN diode and a Schottky diode connected in parallel to each other. The PN diode and the Schottky diode share a same N-type region, a reverse terminal, an N-type extension region, an field oxide region, a gate, and a P-type well in an epitaxial layer. The N-type region and the P-type well form a PN junction, wherein the PN junction has a staggered comb-teeth interface from top view. A metal line extends on the staggered comb-teeth interface and alternatingly contacts the N-type region and the P-type well.