Lateral IGBT Collector Segmentation for Fast Switching
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Solution Overview
Problem
Conventional lateral insulated-gate bipolar transistors (IGBTs) face a trade-off between low on-state voltage and high switching speed, with the double-layered collector region structure leading to increased variation in on-state voltage and limited improvement in switching speed when the fall time is reduced below 0.3 μsec.
Innovation Solution
A N-channel lateral IGBT structure is designed with a collector region having both high and low impurity concentration regions, where the collector electrode is in ohmic contact with the high impurity concentration region and in schottky contact with the low impurity concentration region, reducing hole injection efficiency and allowing for high switching speed without controlling lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the double-layered collector region structure is used with ohmic contact to the collector electrode, then the on-state voltage is reduced, but the switching speed deteriorates and variation of on-state voltage increases
Solution Approach 1:
The collector electrode contact structure is segmented into two distinct regions: a first contact region forming an ohmic contact with the P-well channel layer for low on-state voltage, and a second contact region forming a Schottky contact with the P-well channel layer for high switching speed. This spatial segmentation allows both contact types to coexist without interfering with each other's function.
Solution Approach 2:
Different contact qualities are applied locally to different regions of the collector electrode. The first contact region has ohmic contact properties (low resistance) to minimize voltage drop during conduction, while the second contact region has Schottky contact properties (high resistance, fast carrier extraction) to enable rapid switching. Each region's contact quality is optimized for its specific function.
2Speed
If the fall time is reduced to 0.3 μsec or less, then the switching speed is improved, but the variation of on-state voltage increases
Solution Approach 1:
The collector electrode is divided into two functional regions that work simultaneously: the Schottky contact region enables fast carrier extraction for reduced fall time (0.3 μsec or less), while the ohmic contact region provides stable low-resistance current path that maintains consistent on-state voltage. This segmentation decouples the conflicting requirements of fast switching and voltage stability.
Solution Approach 2:
The contact resistance parameter is changed spatially across the collector electrode surface. The Schottky contact region has high contact resistance to facilitate rapid carrier extraction and reduce fall time, while the ohmic contact region has low contact resistance to maintain stable on-state voltage. This parameter variation in space allows simultaneous achievement of fast switching and voltage consistency.
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 enables a reduction in fall time to 0.3 μsec or less while maintaining the trade-off relationship between switching speed and on-state voltage, achieving a high switching speed without increasing on-state voltage variation.
Implementation Method 1
The collector electrode is in ohmic contact with the high impurity concentration region
Implementation Method 2
The collector electrode is in schottky contact with the low impurity concentration region
Data Source
AI summary
A N-channel lateral insulated-gate bipolar transistor includes a semiconductor substrate, a drift layer, a collector region, a channel layer, an emitter region, a gate insulation film, a gate electrode, a collector electrode, an emitter electrode. The collector region includes a high impurity concentration region having a high impurity concentration and a low impurity concentration region having a lower impurity concentration than the high impurity concentration region. The collector electrode is in ohmic contact with the high impurity concentration region and in schottky contact with the low impurity concentration region.