Superjunction Pillar Structures for Power Device Trade-offs
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Solution Overview
Problem
Power semiconductor devices face challenges in balancing on-resistance and breakdown voltage, particularly in high-voltage applications, where existing technologies struggle to optimize switching speed and performance across different frequency and voltage requirements.
Innovation Solution
The development of superjunction structures with alternately arranged pillars of different conductivity types, including the formation of epitaxial layers, implant regions, and trench filling with semiconductor material, to create a charge balance that enhances breakdown voltage and reduces on-resistance.
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
Solution Approach 1:
The drift region is segmented into multiple cells with alternating P-type and N-type pillars arranged in a superjunction structure. This segmentation allows the electric field to be distributed across multiple depletion regions, enabling high breakdown voltage while maintaining low on-resistance through the combined effect of multiple parallel conduction paths.
Solution Approach 2:
Different regions of the device have different doping types and concentrations - P-type pillars with first doping concentration and N-type pillars with second doping concentration are alternately arranged. This local quality variation creates charge balance that optimizes both breakdown voltage and on-resistance characteristics in different spatial locations within the drift region.
2Loss of energy
If the on-resistance is reduced by decreasing the drift region thickness, then the breakdown voltage decreases
Solution Approach 1:
The drift region is divided into multiple alternating P-type and N-type pillar structures. This segmentation enables the device to achieve low on-resistance through multiple parallel conduction paths while maintaining high breakdown voltage through the cumulative effect of multiple depletion regions formed by the alternating doping structure.
Solution Approach 2:
The invention changes the doping parameters by introducing alternating P-type and N-type regions with specific doping concentrations. This parameter change creates a superjunction structure where the charge balance between positive and negative dopants enables simultaneous optimization of breakdown voltage and on-resistance, overcoming the traditional trade-off.
3Productivity
If charge balance is optimized in the drift region, then switching performance improves
Solution Approach 1:
The drift region is segmented into alternating P-type and N-type pillar structures that can be formed through systematic epitaxial growth and ion implantation processes. This segmentation approach enables precise control of charge balance while following established semiconductor fabrication techniques.
Solution Approach 2:
The alternating P-type and N-type pillars are formed in a predetermined sequence during epitaxial growth and ion implantation steps. This preliminary arrangement of dopant regions ensures optimal charge balance is achieved before device operation, enabling improved switching performance through pre-configured electric field distribution.
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 improves the breakdown voltage and switching performance of power semiconductor devices, allowing for more efficient operation across a range of applications by optimizing charge balance and reducing on-resistance, thus addressing the limitations of existing technologies.
Implementation Method 1
Various techniques for charge balancing in the transistor drift region have been developed
Implementation Method 2
forming a plurality of epitaxial layers of a first conductivity type over a substrate
Implementation Method 3
improving the voltage performance of the transistor while maintaining a low Rds-on poses a challenge
Implementation Method 4
the proportional relationship between the drain-to-source on-resistance Rds-on and the breakdown voltage
Data Source
AI summary
A power device includes a semiconductor region which in turn includes a plurality of alternately arranged pillars of first and second conductivity type. Each of the plurality of pillars of second conductivity type further includes a plurality of implant regions of the second conductivity type arranged on top of one another along the depth of pillars of second conductivity type, and a trench portion filled with semiconductor material of the second conductivity type directly above the plurality of implant regions of second conductivity type.