SiC Super Junction Drift Region for Lower On-Resistance
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Solution Overview
Problem
Conventional power semiconductor devices face a tradeoff between blocking voltage and on-state resistance, with increased blocking voltage leading to higher on-state resistance and conduction losses, and super junction structures face challenges in optimizing doping concentrations and pillar widths for efficient field depletion.
Innovation Solution
The introduction of a semiconductor layer structure with a super junction drift region comprising alternating pillars of different conductivity types, where the doping concentrations are strategically varied to form a composite pillar structure, enhancing charge balance and reducing electric field concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the blocking voltage is increased, then the voltage blocking capability is improved, but the on-state resistance increases and conduction losses increase
Solution Approach 1:
The drift region is segmented into multiple alternating pillars of first and second conductivity types, creating a super junction structure. This segmentation allows the electric field to be distributed across multiple depletion regions, enabling high blocking voltage while maintaining lower on-state resistance through the conductive paths provided by the pillars of the first conductivity type.
Solution Approach 2:
Different regions of the drift region are assigned different conductivity types and doping concentrations. The pillars of the first conductivity type provide conductive paths for current flow, while the pillars of the second conductivity type enhance voltage blocking capability. This local differentiation of properties allows simultaneous optimization of both blocking voltage and on-state resistance.
2Reliability
If super junction structures are used, then blocking voltage capability is improved, but doping concentration optimization becomes complex and manufacturing precision requirements increase
Solution Approach 1:
The invention specifies particular ranges for doping concentrations (first doping concentration for pillars of first conductivity type, second doping concentration for pillars of second conductivity type) and dimensional relationships (pillar widths, spacing, and depths). By defining specific parameter ranges and relationships, the complexity of optimization is reduced while maintaining the super junction benefits.
Solution Approach 2:
The drift region is formed as a composite structure with alternating pillars of different conductivity types, each with specific doping concentrations. This composite approach allows the benefits of both conductivity types to be combined in a controlled manner, simplifying the manufacturing process compared to attempting to optimize a single uniform structure for both high voltage blocking and low resistance.
3Reliability
If alternating pillars of different conductivity types are introduced, then charge balance is improved and electric field distribution is enhanced, but device structure complexity increases
Solution Approach 1:
The drift region is divided into repeating units of alternating pillars, creating a periodic structure that simplifies the analysis and manufacturing process. Each unit cell contains pillars of both conductivity types in a regular pattern, making the complex structure manageable through repetition of standardized elements.
Solution Approach 2:
The alternating pillar structure serves multiple functions simultaneously: the pillars of the first conductivity type provide conductive paths for current flow, while the pillars of the second conductivity type enhance voltage blocking and improve electric field distribution. This multi-functionality is achieved through a single unified structural approach rather than separate components.
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 achieves improved blocking voltage capabilities with reduced on-state resistance and minimized conduction losses, optimizing the tradeoff between blocking voltage and conductivity.
Implementation Method 1
The drift region comprises a lower portion having a first conductivity type that extends throughout the active region, an upper portion having the first conductivity type that extends throughout the active region, and a super junction structure interposed between the lower and upper portions of the drift region
Implementation Method 2
the doping concentrations are strategically varied to form a composite pillar structure, enhancing charge balance and reducing electric field concentrations
Data Source
AI summary
A semiconductor device such as a MOSFET or IGBT comprises a semiconductor layer structure that comprises a drift region, a plurality of well regions having a second conductivity type on the drift region, and a plurality of source regions having a first conductivity type on the well regions. The drift region comprises a plurality of first pillars that have the first conductivity type and a first doping concentration, a plurality of second pillars that have the second conductivity type and a second doping concentration, and a plurality of third pillars that have the first conductivity type and a third doping concentration, The second and third doping concentrations exceed the first doping concentration, and the first, second and third pillars forming a super junction structure in the drift region