Superjunction Pillar Profiling for Core-First Avalanche Breakdown
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Solution Overview
Problem
Existing super-junction devices experience avalanche breakdown primarily in the transition region during single pulse avalanche operations, leading to inefficient energy dissipation and increased costs due to external snubbers or high resistance integration.
Innovation Solution
A super-junction device with an epitaxial layer featuring alternately arranged pillars of different conductivity types, where the upper portions of pillars in the core region exhibit increasing dopant ion concentration and reduced width at the interface with the transition region, shifting the avalanche breakdown to occur first in the core region, thereby improving energy handling during single pulse operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external snubbers or high resistance integration is used to prevent avalanche, then device reliability is improved, but cost and energy losses increase
Solution Approach 1:
The device structure itself provides avalanche protection through the optimized pillar configuration and dopant concentration gradient, eliminating the need for external snubbers or high resistance integration. The transition region with decreasing pillar width and increasing dopant concentration automatically controls avalanche breakdown to occur in the core region rather than the transition region, making the device self-protecting and reducing external protection components.
2Reliability
If pillar width is reduced at the transition region interface, then avalanche breakdown is shifted to the core region, but manufacturing precision requirements increase
Solution Approach 1:
The pillar width is optimized locally at the transition region interface rather than uniformly throughout the device. Specifically, pillars in the transition region have decreased width compared to pillars in the core region, creating a localized geometric feature that directs electric field distribution and avalanche breakdown to the desired location while maintaining overall device functionality.
Solution Approach 2:
The dopant concentration is varied as a function of position, with increasing concentration in the transition region pillars compared to core region pillars. This parameter gradient, combined with the width variation, creates a controlled electric field distribution that guides avalanche breakdown to the core region. The gradual parameter change reduces abrupt transitions and associated manufacturing challenges.
3Reliability
If dopant ion concentration is increased in upper portions of pillars, then voltage endurance in transition region is improved, but device complexity increases
Solution Approach 1:
The dopant concentration is optimized locally in specific regions: upper portions of pillars in the transition region have increased dopant concentration to enhance voltage endurance and electric field control, while pillars in the core region maintain lower concentration to facilitate avalanche breakdown. This localized differentiation creates distinct functional zones within the device.
Solution Approach 2:
The device is segmented into distinct functional regions (transition region and core region) with different dopant concentration characteristics. The transition region pillars are further segmented into upper portions with higher concentration and lower portions with lower concentration, creating a vertical gradient that controls electric field distribution and avalanche behavior.
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 enhances voltage endurance in the transition region and ensures avalanche breakdown occurs in the core region, improving single pulse avalanche performance by reducing peak electric field strength and increasing the probability of breakdown in the core region, thus enhancing the device's energy handling capabilities.
Implementation Method 1
avalanche breakdown to occur first in its core region and is thus improved in terms of energy during avalanche for single pulse (EAS) performance
Implementation Method 2
reducing peak electric field strength in the transition region and thus increased voltage endurance
Implementation Method 3
upper portions of some of the pillars of the second conductivity type in the core region in proximity to the transition region exhibit a dopant ion concentration increasing from one pillar to the next
Data Source
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AI summary
A super-junction device and a method of fabricating such a device are disclosed, in which a pillar of a second conductivity type situated at an interface between a transition region and a core region is narrowed in width across at least an upper thickness thereof, thereby reducing peak electric field strength in the transition region, increasing voltage endurance of the transition region and preventing the occurrence of avalanche breakdown first in the transition region. Additionally, a dopant ion concentration profile increasing in the direction from the transition region to the core region is created across upper portions of some pillars of the second conductivity type in the core region, which increases the presence of the dopant of the second conductivity type around the surface of the core region and thus stops a vertical electric field before it can reach wells of the second conductivity type. That is, an effective epitaxial thickness of the core region is reduced, which results in lower voltage endurance thereof. In this way, it is ensured that avalanche breakdown occurs first in the core region, resulting in improved EAS performance.