Semiconductor Edge Termination via Trench Ladder Networks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power semiconductor devices face damage due to conduction initiation at the edge of the semiconductor die when the reverse bias exceeds the breakdown voltage, leading to potential destruction and alteration of electrical characteristics.
Innovation Solution
The implementation of a high-voltage termination structure with a peripheral voltage-spreading network, utilizing trench structures with current-limiting elements and permanent charge in the trench-wall dielectric, connected in a series-parallel ladder configuration, to increase breakdown voltage and reduce edge conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional edge termination is used in power semiconductor devices, then the device structure is simple, but the breakdown voltage at the edge is insufficient leading to conduction initiation and device damage
Solution Approach 1:
The termination region is divided into multiple discrete cells arranged in a grid pattern, with each cell containing individual trenches and current-limiting structures. This segmentation allows the edge termination function to be distributed across many small units, increasing the effective breakdown voltage at the edge while maintaining a manageable overall structure.
Solution Approach 2:
Trench structures filled with dielectric material and containing permanent charge are introduced as intermediary elements between the active device region and the edge termination region. These trenches act as mediators that distribute and control the electric field, preventing direct conduction at the edge while managing the complexity through standardized trench designs.
2Reliability
If the breakdown voltage is increased to prevent edge conduction, then device durability improves, but the area required for termination increases excessively
Solution Approach 1:
The termination structure implements local quality by creating regions of different electrical characteristics within the termination area. Specifically, the trench structures and current-limiting elements are strategically positioned to provide enhanced field control where needed, while other areas use simpler termination approaches. This allows high durability to be achieved with minimized total termination area.
Solution Approach 2:
The invention transitions from traditional two-dimensional planar termination to a three-dimensional structure by introducing vertical trenches filled with dielectric material containing permanent charge. This dimensional change allows the termination function to be achieved with reduced planar area, as the electric field control is extended into the vertical dimension through the trench structures.
3Manufacturing precision
If permanent charge is introduced in trench-wall dielectric, then voltage distribution is improved, but manufacturing complexity increases
Solution Approach 1:
Permanent charge is introduced into the trench-wall dielectric during the fabrication process itself, rather than requiring subsequent complex charging steps. The ion implantation or charge injection is performed as a preliminary action during trench formation, establishing the required voltage distribution characteristics before the device is fully assembled and operated.
Solution Approach 2:
The invention controls voltage distribution by changing the electrical parameters of the trench structures, specifically by adjusting the amount and distribution of permanent charge within the dielectric material. By varying charge density, trench depth, and dielectric properties, precise voltage distribution can be achieved while using standard semiconductor fabrication techniques.
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 solution effectively increases the breakdown voltage at the edge of the active device area, improving durability under electrical and electromagnetic transients, and reducing excessive area usage in termination, while maintaining high net breakdown voltage.
Implementation Method 1
permanent charge in a trench-wall dielectric
Implementation Method 2
current-limiting structures connected in series with a semiconductor material
Data Source
AI summary
A high-voltage termination structure includes a peripheral voltage-spreading network. One or more trench structures are connected at least partly in series between first and second power supply voltages. The trench structures include first and second current-limiting structures connected in series with a semiconductor material, and also includes permanent charge in a trench-wall dielectric. The current-limiting structures in the trench structures are jointly connected in a series-parallel ladder configuration. The current-limiting structures, in combination with the semiconductor material, provide a voltage distribution between the core portion and the edge portion.