Superjunction Pillar Structures for Power Device Trade-offs
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Solution Overview
Problem
Power semiconductor devices, such as MOSFETs and IGBTs, face challenges in balancing on-resistance and breakdown voltage, particularly at high voltages, where existing technologies struggle to improve voltage performance while maintaining low on-resistance and achieving optimal switching speed.
Innovation Solution
The development of superjunction structures with alternately arranged pillars of different conductivity types, formed through epitaxial layers and trench filling techniques, which allow for precise control of charge balance and electric field distribution, enabling improved breakdown voltage and switching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional charge balancing structures are used in the transistor drift region, then breakdown voltage is improved, but on-resistance increases
Solution Approach 1:
The drift region is segmented into multiple columns with alternating conductivity types (N-type and P-type) arranged in a superjunction structure. This segmentation allows independent control of charge balancing while maintaining low on-resistance paths, resolving the contradiction between achieving high breakdown voltage and maintaining low on-resistance
Solution Approach 2:
Different regions of the drift region are assigned different conductivity types and doping concentrations to create localized charge balancing. The alternating N-type and P-type columns provide local charge compensation that enables high breakdown voltage without increasing overall on-resistance, as each local region contributes differently to the electric field distribution
2Reliability
If IGBT is used for applications greater than 400 volts, then on-resistance is reduced, but switching speed decreases
Solution Approach 1:
The superjunction structure provides multi-functionality by combining the voltage-blocking capability of IGBT with the switching speed characteristics of MOSFET. The alternating conductivity type columns enable the device to achieve both low on-resistance and fast switching speed, making it suitable for high voltage applications with high frequency requirements
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 the breakdown voltage and switching performance of power semiconductor devices, ensuring stable operation under high voltage conditions and reducing on-resistance, thus addressing the limitations of existing technologies.
Implementation Method 1
a plurality of alternately arranged pillars of first and second conductivity type... precise control of charge balance and electric field distribution
Implementation Method 2
precise control of charge balance and electric field distribution, enabling improved breakdown voltage
Implementation Method 3
each of the plurality of pillars of second conductivity type further includes a plurality of implant regions of the second conductivity type
Implementation Method 4
formed through epitaxial layers and trench filling techniques
Data Source
AI summary
In a general aspect, a power device can include at least one N-type epitaxial layer disposed on a substrate and a plurality of N-pillars and P-pillars that define alternating P-N-pillars in the at least one N-type epitaxial layer. The power device can also include an active region and a termination region, where the termination region surrounds the active region. The alternating P-N-pillars can be disposed in both the active region and the termination region, where the termination region can include a predetermined number of floating P-pillars.