SiC JBS Diode with Polysilicon Barrier for Leakage Reduction
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Solution Overview
Problem
Conventional silicon carbide Schottky diodes face issues with reverse leakage currents and catastrophic failure under high reverse voltage, limiting their voltage blocking ability and switching speed, particularly compared to silicon PIN diodes.
Innovation Solution
The development of a junction barrier Schottky (JBS) diode structure incorporating a p-type polysilicon region forming a P-N heterojunction with the drift region, where the Schottky junction turns on at a lower forward voltage than the P-N heterojunction, and a guard ring termination region is used to manage electric field crowding and reduce reverse leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a Schottky contact is formed directly on the n- drift layer to achieve fast switching speed, then switching speed is improved, but reverse leakage current increases and voltage blocking capability deteriorates
Solution Approach 1:
The device is segmented into multiple functional regions: a Schottky contact region for fast switching and a JBS region with p+ barrier layers for voltage blocking. The p+ barrier layers are distributed across the drift layer to create localized junctions that prevent depletion region interaction with the surface, thereby reducing reverse leakage while maintaining fast switching capability in the Schottky region.
Solution Approach 2:
Different regions of the device are given different properties: the Schottky contact region is optimized for low forward voltage drop and fast switching, while the JBS regions with p+ barrier layers are optimized for high voltage blocking and low reverse leakage. This local differentiation allows the device to exhibit both fast switching and high reliability characteristics in their respective regions.
2Reliability
If ion implantation is used to form p+ barrier regions to reduce reverse leakage current, then reverse leakage is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The p+ barrier regions are formed by ion implantation through a patterned mask before the final device assembly. This preliminary formation of barrier regions establishes the JBS structure early in the manufacturing process, enabling subsequent steps to build upon this foundation and reducing overall manufacturing complexity.
3Power
If the depletion region is allowed to extend to the edge of the device to maximize active area, then current handling capability is improved, but electric field crowding causes premature breakdown and reduces voltage blocking ability
Solution Approach 1:
The device active area is segmented into Schottky contact regions and JBS regions. The JBS regions with p+ barrier layers are positioned at strategic locations to terminate depletion regions before they reach the device edges, preventing electric field crowding and premature breakdown while maintaining adequate current handling capability in the Schottky regions.
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 JBS diode structure enhances voltage blocking capability, reduces reverse leakage currents, and maintains fast switching speeds characteristic of Schottky diodes, while providing surge current handling and improved reliability by controlling the forward voltage drop and preventing current runaway.
Implementation Method 1
A Schottky contact is formed on the drift layer and forms a Schottky junction with the drift layer
Implementation Method 2
The p-type junction barrier region includes a p-type polysilicon region forming a P-N heterojunction with the drift layer
Implementation Method 3
A guard ring termination region is formed surrounding the Schottky junction active region. The purpose of junction termination region is to reduce or prevent electric field crowding at the edges of the Schottky junction
Data Source
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AI summary
An electronic device includes a silicon carbide layer including an n-type drift region therein, a contact forming a Schottky junction with the drift region, and a p-type junction barrier region on the silicon carbide layer. The p-type junction barrier region includes a p-type polysilicon region forming a P-N heterojunction with the drift region, and the p-type junction barrier region is electrically connected to the contact.