Power Schottky Diode Junction Layout for Low Reverse Leakage
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Solution Overview
Problem
Power Schottky diodes face a tradeoff between on-state resistance and reverse leakage current, with increased reverse blocking voltage rating often leading to higher on-state resistance and potential avalanche breakdown.
Innovation Solution
The design incorporates deeper blocking junctions formed using channeled ion implantation, a current spreading layer with higher dopant concentration than the drift region, and a buried current spreading layer to reduce electric field intensity and on-state resistance while maintaining low reverse leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reverse blocking voltage rating is increased, then the reverse leakage current is reduced, but the on-state resistance increases
Solution Approach 1:
The patent applies local quality by creating a current spreading layer with higher dopant concentration specifically in regions adjacent to blocking junctions, while maintaining lower dopant concentration in the bulk drift region. This localized doping strategy reduces on-state resistance at critical current flow paths without compromising the reverse blocking voltage rating determined by the bulk drift region.
Solution Approach 2:
The patent changes the dopant concentration parameter spatially within the drift region. By varying the dopant concentration from high near blocking junctions to low in the bulk, the device achieves both low on-state resistance (requiring high doping) and high reverse blocking voltage rating (requiring low doping), resolving the contradiction between these two parameters.
2Reliability
If deeper blocking junctions are formed, then the reverse leakage current is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by forming the current spreading layer with elevated dopant concentration before or during blocking junction formation. This pre-positioned high-doping region is strategically placed to address current crowding at blocking junction corners, reducing reverse leakage current without requiring additional complex processing steps later.
Solution Approach 2:
The current spreading layer acts as an intermediary region between the metal contact and the drift region. This intermediate layer with graded or elevated doping provides a transition zone that manages electric field distribution and current flow, reducing reverse leakage current while simplifying the overall device structure compared to directly forming deep blocking junctions in uniformly doped material.
3Object-generated harmful factors
If the dopant concentration in the drift region is increased, then the on-state resistance is reduced, but the reverse blocking voltage rating decreases
Solution Approach 1:
The patent implements local quality by creating spatial variation in dopant concentration within the drift region. The current spreading layer adjacent to blocking junctions has higher dopant concentration to reduce on-state resistance, while the bulk drift region maintains lower dopant concentration to preserve reverse blocking voltage rating. This localized differentiation resolves the contradiction between these two opposing requirements.
Solution Approach 2:
The drift region is segmented into functionally distinct zones: a current spreading layer with higher doping near blocking junctions for low on-state resistance, and a bulk drift region with lower doping for high reverse blocking voltage rating. This segmentation allows each zone to optimize its local function without compromising the other, resolving the contradiction between on-state resistance and reverse blocking voltage rating.
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 effectively reduces reverse leakage currents without significantly increasing on-state resistance, enhancing the performance of power Schottky diodes by improving both reverse bias and forward bias characteristics.
Implementation Method 1
The current spreading layer has a first conductivity type dopant concentration that is at least 1.5 times greater than a first conductivity type dopant concentration of the drift region
Implementation Method 2
The design incorporates deeper blocking junctions formed using channeled ion implantation
Data Source
AI summary
A Schottky diode includes a semiconductor layer structure that is interposed between first and second contacts. The semiconductor layer structure comprises a current spreading layer having a first conductivity type, a drift region between the second contact and the current spreading layer, the drift region having the first conductivity type, and a first blocking junction having a second conductivity type that is opposite the first conductivity type, the first blocking junction extending downwardly from an upper surface of the semiconductor layer structure. The current spreading layer has a first conductivity type dopant concentration that is at least 1.5 times greater than a first conductivity type dopant concentration of the drift region and the current spreading layer vertically overlaps at least a portion of a lower half of the first blocking junction.