Edge Termination Trench Profile for Uniform Avalanche Breakdown
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Solution Overview
Problem
Transistor devices for power applications face challenges in avalanche robustness and on-state resistance due to edge effects and uneven electric field distribution, leading to potential overheating and device failure.
Innovation Solution
A semiconductor device with an active area surrounded by an edge termination region, featuring columnar trenches with a stepped field dielectric profile and inactive cells with a drift region and body region, which helps in distributing avalanche breakdown evenly and reducing edge effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional edge termination structure is used to remove discontinuities at the edge, then edge effects are reduced, but avalanche breakdown may still occur preferentially in specific areas due to non-uniform electric field distribution
Solution Approach 1:
The patent applies local quality by varying the field dielectric thickness within the columnar trench based on position. The field dielectric has a first thickness in an upper region and a second thickness in a lower region, with the second thickness being greater than the first. This non-uniform thickness distribution is specifically designed to compensate for the non-uniform electric field distribution in different regions of the semiconductor device, thereby achieving more uniform electric field distribution across the entire device area and improving avalanche robustness.
2Device complexity
If avalanche breakdown occurs in a specific area with lower breakdown voltage, then the device structure is simpler, but the critical temperature is reached more easily causing device failure
Solution Approach 1:
The patent applies parameter changes by modifying the field dielectric thickness parameter within the columnar trench. The field dielectric thickness varies from a first thickness in the upper region to a second thickness in the lower region. This parameter variation changes the electric field distribution characteristics, causing avalanche breakdown to occur more uniformly across the entire active area rather than concentrating in specific areas, thereby preventing localized overheating and device failure while maintaining structural simplicity.
3Ease of manufacture
If the field dielectric thickness is uniform throughout the columnar trench, then the manufacturing process is simpler, but the electric field distribution remains non-uniform leading to preferential avalanche breakdown
Solution Approach 1:
The patent implements local quality by creating a position-dependent field dielectric thickness profile within the columnar trench. The field dielectric has a first thickness in an upper region and a second thickness in a lower region, with the second thickness being greater than the first. This local variation in dielectric thickness is specifically designed to compensate for the non-uniform electric field distribution, achieving more uniform electric field characteristics across different regions of the device while maintaining compatibility with standard semiconductor manufacturing processes.
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 solution enhances avalanche robustness and reduces on-state resistance, improving the overall performance and reliability of transistor devices by evenly distributing avalanche breakdown and mitigating edge effects.
Implementation Method 1
Each field dielectric of the first columnar trenches has a first thickness in an upper region of the field plate and a second thickness in a lower region of the field plate, the second thickness being greater than the first thickness
Implementation Method 2
Avalanche breakdown is the phenomenon of current multiplication when a semiconductor device is subject to high electric fields. In the avalanche state, a high amount of power may be dissipated in the transistor device which may finally result in a destruction due to overheating
Data Source
Figure 1A
Figure 1B~2B
Figure 3A
AI summary
In an embodiment, a semiconductor device is provided that comprises an active area and an edge termination region laterally surrounding the active area. The active area comprises a plurality of active transistor cells. The edge termination region comprises one or more inactive cells, each inactive cell comprising a first columnar trench and a first termination mesa arranged adjacent to the first columnar trench. Each first columnar trench comprises a base, a side wall, a field plate, and a field dielectric arranged on the base and the side wall and surrounding the field plate. Each first termination mesa comprises a drift region of a first conductivity type and a body region of a second conductivity type arranged above the drift region. Each field dielectric of the first columnar trenches has a first thickness in an upper region of the field plate and a second thickness in a lower region of the field plate, the first thickness being smaller than the second thickness.