Shielded Buried Grid in SiC for JBSD Field Peak Suppression
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Solution Overview
Problem
Buried grid technology for high voltage wide band gap devices fails to fully protect sensitive areas like Schottky contacts from high electric fields, limiting device performance by allowing electric field peaks to reach these areas, and there is a need to improve the trade-off between current conducting and voltage blocking characteristics.
Innovation Solution
A buried grid structure in wide band gap materials with regularly spaced doped parts and spaces, where shields are positioned to cover the middle points between adjacent grid parts, reducing electric field peaks and incorporating shielding insulators or doped surface grids to enhance shielding without additional lithographic steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buried grid structure is used to protect sensitive parts from high electric fields, then voltage blocking capability is improved, but leakage current increases and capacitance increases
Solution Approach 1:
The shield is segmented into multiple regions: a first region with doping concentration matching the drift layer and a second region with higher doping concentration. This segmentation allows different portions of the shield to perform different functions - the first region maintains voltage blocking while the second region suppresses leakage current and reduces capacitance.
Solution Approach 2:
Different doping concentrations are applied to different regions of the shield. The first region has doping concentration matching the drift layer to maintain electric field distribution for voltage blocking, while the second region has higher doping concentration specifically at locations where leakage current and capacitance are problematic, providing localized improvement without compromising overall voltage blocking.
2Reliability
If grid spacing is reduced to improve voltage blocking, then voltage blocking capability increases, but electric field peaks between grids increase affecting Schottky contact
Solution Approach 1:
The shield acts as an intermediary element positioned between the buried grid and the Schottky contact. It intercepts and redistributes the electric field, preventing direct field lines from concentrating at the Schottky contact. The specific doping profile of the shield mediates the electric field distribution, reducing peaks while maintaining overall voltage blocking capability.
3Object-generated harmful factors
If shield doping concentration is increased to reduce leakage current, then leakage current decreases, but voltage blocking capability may be compromised
Solution Approach 1:
The shield is divided into regions with different doping concentrations. The first region maintains doping concentration matching the drift layer to preserve voltage blocking capability, while the second region uses higher doping concentration specifically to suppress leakage current. This segmentation allows both objectives to be achieved simultaneously in different spatial locations.
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 achieves better trade-off between current conducting and voltage blocking characteristics, reducing forward resistance and leakage current, while maintaining voltage blocking capability at higher temperatures with improved current density and surge current capability.
Implementation Method 1
a buried grid (2) being a regularly spaced pattern of parts (2) of doped wide band gap material of a first conductivity type (p or n)
Implementation Method 2
calculating the electric field around the buried grid (2) assuming that a voltage potential difference occurs over the layer
Implementation Method 3
at least one shield (4) covers at least a middle point between two adjacent parts of the buried grid (2)... to protect the sensitive part of high voltage wide band gap devices from the high electric field
Data Source
AI summary
There is disclosed a structure in a wide band gap material such as silicon carbide wherein there is a buried grid and shields covering at least one middle point between two adjacent parts of the buried grid, when viewed from above. Advantages of the invention include easy manufacture without extra lithographic steps compared with standard manufacturing process, an improved trade-off between the current conduction and voltage blocking characteristics of a JBSD comprising the structure.