Superjunction Power Devices with Alternating Pillars for High Voltage
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Solution Overview
Problem
Power semiconductor devices face challenges in achieving optimal on-resistance and breakdown voltage performance, particularly for applications above 400 volts, where existing technologies struggle to balance these parameters effectively.
Innovation Solution
The development of power devices with alternating conductivity type pillars, formed through epitaxial layers and trench filling processes, which include multiple implant regions and trench structures to optimize charge balance and electric field distribution, allowing for improved breakdown voltage and switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breakdown voltage is improved by increasing the drift region thickness, then the on-resistance increases, but the switching speed decreases
Solution Approach 1:
The drift region is segmented into multiple cells with alternating P-type and N-type pillars arranged in a grid pattern. This segmentation allows the electric field to be distributed across multiple depletion regions, enabling high breakdown voltage while maintaining low on-resistance through the parallel conduction paths provided by the cellular structure.
Solution Approach 2:
The patent introduces localized doping regions with alternating conductivity types (P-type and N-type pillars) within the drift region. Each local region has optimized doping concentrations and pillar dimensions tailored to specific electrical requirements, creating areas of high electric field control near the junction and different characteristics in the bulk drift region, thereby achieving both high breakdown voltage and fast switching.
2Productivity
If the on-resistance is reduced by decreasing the drift region thickness, then the breakdown voltage decreases, but the device performance improves for high frequency applications
Solution Approach 1:
The drift region is divided into multiple cellular units with alternating P-N pillars, creating multiple parallel conduction paths. This segmentation reduces the effective resistance while maintaining the physical thickness required for high breakdown voltage, enabling both high-frequency operation and high voltage capability.
Solution Approach 2:
The patent creates a composite doped structure within the drift region by integrating P-type and N-type pillars in an alternating pattern. This composite structure combines the beneficial electrical characteristics of both doping types, achieving low on-resistance through enhanced carrier concentration and high breakdown voltage through extended depletion regions, thus supporting both high frequency and high voltage applications.
3Reliability
If alternating conductivity type pillars are introduced to balance charge, then the breakdown voltage improves, but the device complexity increases
Solution Approach 1:
The drift region is segmented into repeating cellular units with a standardized alternating P-N pillar pattern. This segmentation transforms the complex charge balancing requirement into a repetitive, modular structure that can be manufactured using standard semiconductor fabrication techniques, reducing overall device complexity while achieving the desired charge balance and high breakdown voltage.
Solution Approach 2:
The alternating P-N pillar structure serves multiple functions simultaneously: it provides charge balance in the drift region, extends the depletion region width for high breakdown voltage, creates multiple conduction paths for low on-resistance, and enables fast switching through reduced stored charge. This multi-functionality reduces the need for separate structural elements, thereby managing device complexity.
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 speed of power semiconductor devices, ensuring stable performance across various applications by effectively managing charge balance and electric field distribution within the device.
Implementation Method 1
charge balance and electric field distribution
Implementation Method 2
The superjunction approach allows for a more uniform distribution of the electric field across the drift region and extends the depletion region
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 processes
Data Source
AI summary
In a general aspect, a power device can include an epitaxial layer of a first conductivity type, an active region, a termination region surrounding the active region, a plurality of trenches disposed in the epitaxial layer, and silicon material of a second conductivity type disposed in the plurality of trenches. The silicon material of the second conductivity type and a plurality of mesas defined in the epitaxial layer by the trenches, can define a plurality of concentric octagon-shaped pillars of alternating conductivity type, a first portion of the pillars being disposed in the active region and a second portion of the pillars being disposed in the termination region. Sidewalls of the plurality of trenches can define a first four legs and a second four legs of each of the pillars. The sidewalls can have a same crystallographic plane direction.