SiC Schottky Diode Structure for Low Leakage and High 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 while maintaining high switching speeds.
Innovation Solution
A Schottky diode design featuring a Tantalum (Ta) Schottky layer and a silicon carbide (SiC) drift layer with a junction barrier array and edge termination structure, including guard rings and recesses, to reduce barrier height and enhance voltage blocking capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a Schottky barrier is used to achieve low forward voltage drops and high switching speeds, then forward-biased performance is improved, but reverse-biased voltage ratings are limited and leakage currents increase
Solution Approach 1:
The device is segmented into multiple functional regions: a drift region for voltage blocking, a Schottky barrier region for low forward voltage drop, and a junction barrier region for leakage control. This segmentation allows each region to be optimized for its specific function, resolving the contradiction between forward-biased performance and reverse-biased reliability.
Solution Approach 2:
The invention uses a composite structure combining metal (Schottky barrier) and semiconductor materials with specific doping profiles. The metal-semiconductor junction provides low forward voltage drop while the doped semiconductor regions provide high reverse voltage blocking capability, creating a composite device that achieves both contradictory performance goals.
2Speed
If a Schottky barrier is used to achieve high switching speeds through low capacitance, then switching performance is improved, but reverse-biased leakage currents increase
Solution Approach 1:
The junction barrier region acts as an intermediary between the Schottky barrier and the drift region. It mediates the conflicting requirements by providing a transition zone that maintains the low capacitance needed for high switching speeds while introducing sufficient doping to reduce reverse leakage currents through field control.
Solution Approach 2:
Different regions of the device have different doping qualities: the Schottky region has low doping for low capacitance and high switching speed, while the junction barrier region has higher doping to control leakage. This local variation in material quality allows simultaneous optimization of switching speed and leakage reduction.
3Ease of manufacture
If traditional Schottky diode structures are used to maintain simplicity, then manufacturing cost is reduced, but performance limitations persist
Solution Approach 1:
The drift region serves multiple functions: it provides voltage blocking capability, controls electric field distribution, and enables high current handling. This multi-functionality allows a single region to address multiple performance requirements, improving device performance without proportionally increasing manufacturing complexity.
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 design achieves lower forward voltage drops, reduced reverse leakage currents, and improved voltage blocking, enabling higher performance and efficiency with controlled avalanche currents, while maintaining fast switching speeds.
Implementation Method 1
the metal for the Schottky layer and the semiconductor material for the drift layer are selected to provide a low barrier height Schottky junction between the drift layer and the Schottky layer
Implementation Method 2
The drift layer has a first surface associated with the active region and provides an edge termination region. The edge termination region is laterally adjacent the active region
Implementation Method 3
When the rectifier is reverse-biased, the depletion regions along the PN junctions merge to occupy the entire width of the mesas, thereby protecting the rectifying interface from barrier lowering and resulting current leakage
Data Source
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AI summary
A semiconductor device (10) comprises a drift layer (22) having a first surface with an active region (14) and a plurality of junction barrier element recesses (40), the drift layer being doped with a doping material of a first conductivity type and associated with an edge termination region (16) that is substantially laterally adjacent the active region. A Schottky layer (24) is over the active region of the first surface to form a Schottky junction. A plurality of first doped regions (30) extend into the drift layer about corresponding ones of the plurality of junction barrier element recesses (40) wherein the plurality of first doped regions are doped with a doping material of a second conductivity type, which is opposite the first conductivity type, and form an array of junction barrier elements in the drift layer below the Schottky junction. A well (34) ia formed in the drift layer in the edge termination region, the well having guard rings (36) and being doped with the doping material of the second conductivity type where the plurality of guard rings are formed in the well, wherein the guard rings are coplanar with the junction barrier element recesses.