Split Support Shield Structures for Trench Gate Field Control
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Solution Overview
Problem
Power semiconductor devices face challenges with gate insulating layer degradation due to high electric fields, leading to potential device failure, especially at the corners of gate trenches where electric field concentrations are highest.
Innovation Solution
The implementation of support shielding structures of a second conductivity type, which are spaced apart from the sidewalls of gate trenches, helps to reduce electric field levels and prevent degradation of the gate insulating layer. These shielding structures can be formed by ion implantation or deposition and may extend into the drift region beyond the bottom shielding structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate trenches are formed in the semiconductor structure to create vertical channel devices, then device performance is enhanced, but electric field concentration at the trench corners causes gate insulating layer degradation and potential device failure
Solution Approach 1:
The patent introduces support shielding structures as intermediary elements positioned between the gate trenches and the drift region. These shielding structures act as mediators that redistribute and reduce the electric field concentration at the gate trench corners, thereby protecting the gate insulating layer from degradation while maintaining the beneficial vertical channel device performance
Solution Approach 2:
The patent segments the shielding function by introducing separate support shielding structures distinct from the gate trenches themselves. Rather than relying on a single continuous shielding approach, the gate region is divided into multiple unit cells with individual support shielding structures, allowing localized electric field management at each trench corner
2Reliability
If support shielding structures are added to reduce electric field levels, then gate insulating layer protection is improved, but device structure and manufacturing complexity increase
Solution Approach 1:
The support shielding structures serve multiple functions simultaneously: they reduce electric field concentration at gate trench corners, provide additional current conduction paths during avalanche conditions, and can be integrated with existing drift region processing. This multi-functionality justifies the added structural elements by delivering multiple benefits from a single design feature
Solution Approach 2:
The patent optimizes the support shielding structure parameters (such as doping concentration, depth, and spacing from gate trenches) to achieve effective electric field reduction while minimizing the number of additional processing steps. By carefully controlling these parameters, the structure provides protection without excessive complexity
3Reliability
If support shielding structures are positioned close to gate trenches to maximize electric field reduction, then gate insulating layer protection is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The support shielding structures are formed using preliminary ion implantation or deposition processes before final gate trench definition, or are formed in the same processing step with shared alignment references. This preliminary positioning action establishes the critical spacing between shielding structures and gate trenches, reducing the need for high-precision subsequent alignment operations
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
The use of support shielding structures effectively reduces the risk of gate insulating layer breakdown, enhances the reliability of power semiconductor devices, and improves their switching characteristics by providing a lower resistance current path under avalanche conditions.
Implementation Method 1
high electric fields, leading to potential device failure, especially at the corners of gate trenches where electric field concentrations are highest
Implementation Method 2
improves their switching characteristics by providing a lower resistance current path under avalanche conditions
Data Source
AI summary
A power semiconductor device includes a semiconductor structure having a drift region of a first conductivity type. Gate trenches respectively comprising sidewalls and a bottom surface therebetween extend in a first direction in the semiconductor structure, and support shielding structures of a second conductivity type extend in the first direction in the semiconductor structure spaced apart from the sidewalls of the gate trenches. At least two of the support shielding structures are between immediately adjacent pairs of the gate trenches, or at least two of the gate trenches are between immediately adjacent pairs of the support shielding structures. For example, the support shielding structures may include first and second support shielding structures that are free of the gate trenches therebetween, or the gate trenches may include first and second gate trenches that are free of the support shielding structures therebetween. Related devices and fabrication methods are also discussed.