SiC Edge Termination Recesses for Voltage Blocking
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Solution Overview
Problem
Schottky diodes face limitations in reverse-biased voltage ratings and high reverse-biased leakage currents, necessitating improvements in performance and cost reduction.
Innovation Solution
The semiconductor device incorporates an edge termination structure with doped guard rings and junction barrier arrays in a silicon carbide substrate, featuring a Schottky layer with a low barrier height, and a thinned substrate design to enhance voltage blocking and reduce leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Schottky diode structure is used, then manufacturing is simpler, but reverse-biased voltage rating is low and leakage current is high
Solution Approach 1:
The edge termination structure is segmented into multiple components: junction barrier Schottky elements, guard rings, and recesses positioned at different locations and depths. This segmentation allows each element to perform a specific function in managing electric fields, thereby achieving high voltage ratings and low leakage currents through coordinated action of distributed elements rather than a single complex structure
Solution Approach 2:
The patent introduces vertical dimensionality by forming recesses that extend into the drift layer at different depths. This multi-level vertical arrangement allows electric field management in three-dimensional space, with shallower elements handling surface fields and deeper elements managing bulk fields, thereby achieving superior voltage blocking without proportionally increasing lateral device footprint
2Reliability
If deeper doped regions are formed to improve voltage blocking, then reverse breakdown voltage increases, but manufacturing complexity increases
Solution Approach 1:
Recesses are formed in the drift layer before doping is performed. This preliminary action creates pre-defined cavities that guide subsequent doping material to specific locations and depths. The recesses act as templates that ensure dopants are deposited only where needed and to the correct depth, simplifying the doping process compared to attempting to form deep doped regions directly without pre-formed structures
Solution Approach 2:
Different regions of the drift layer are doped with different doping types and concentrations tailored to local requirements. Junction barrier Schottky elements use one doping configuration while guard rings use another, and elements at different depths have different doping profiles. This localized customization of doping quality allows each region to optimize its electrical characteristics for its specific function in voltage blocking and leakage reduction
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 achieves improved reverse breakdown voltage, reduced leakage currents, and controlled avalanche currents, while maintaining fast switching speeds and efficient current handling, thus enhancing the overall performance and cost-effectiveness of Schottky diodes.
Implementation Method 1
a low barrier height Schottky junction between the drift layer and the Schottky layer
Data Source
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AI summary
Elements of an edge termination structure, such as multiple concentric guard rings, are effectively doped regions in a drift layer. To increase the depth of these doped regions, individual recesses may be formed in a surface of the drift layer where the elements of the edge termination structure are to be formed. Once the recesses are formed in the drift layer, these areas about and at the bottom of the recesses are doped to form the respective edge termination elements.