SiC Schottky Diode Segmented p+ Regions Reduce On-Resistance
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Solution Overview
Problem
The existing Schottky barrier diodes face increased on-resistance due to a reduced contact area between the Schottky electrode and the n− drift layer, and difficulties in reducing the interval between p+ regions, which affects the leakage current and breakdown voltage.
Innovation Solution
The Schottky barrier diode design includes an n− type epitaxial layer on an n+ type silicon carbide substrate with a first p+ region formed in a lattice shape and a second p+ region formed in a quadrangle shape surrounding the edge of the n type epitaxial layer, both in contact with each other, to maximize the Schottky junction area and reduce on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p+ region is formed in the n- drift layer to improve leakage current blocking, then breakdown voltage is improved, but the contact area between Schottky electrode and n- drift layer is reduced, increasing on-resistance
Solution Approach 1:
The p+ region is segmented into two distinct parts: a first p+ region formed in the n- drift layer for leakage current blocking, and a second p+ region formed in the n type epitaxial layer that extends the Schottky junction area. This segmentation allows each p+ region to fulfill different functions simultaneously, resolving the contradiction between leakage blocking and on-resistance reduction.
Solution Approach 2:
The second p+ region is formed in the n type epitaxial layer above the n- drift layer, adding a vertical dimension to the Schottky junction area extension. This dimensional approach allows the Schottky electrode to contact both the n type epitaxial layer and n- drift layer through the second p+ region, effectively increasing the current path area without compromising the leakage blocking function of the first p+ region.
2Reliability
If the interval between p+ regions is reduced to improve leakage current blocking, then breakdown voltage is improved, but manufacturing complexity increases
Solution Approach 1:
The p+ regions are segmented into two functionally distinct regions with different spacing requirements. The first p+ region in the n- drift layer provides leakage blocking, while the second p+ region in the n type epitaxial layer extends the Schottky junction. This segmentation allows optimal spacing for each function, simplifying manufacturing by eliminating the need to uniformly reduce intervals across the entire device structure.
3Loss of energy
If the Schottky junction area is maximized to reduce on-resistance, then forward conduction is improved, but the structure becomes more complex
Solution Approach 1:
The Schottky electrode is merged with both the n type epitaxial layer and the n- drift layer through the second p+ region, creating a unified current path that maximizes the effective Schottky junction area. This merging approach extends the current path without requiring separate structures, thereby reducing structural complexity while achieving lower on-resistance.
Solution Approach 2:
The Schottky junction area is extended in the vertical dimension by forming the second p+ region in the n type epitaxial layer. This allows the Schottky electrode to contact multiple layers at different heights, effectively increasing the junction area without expanding the horizontal footprint, thus avoiding increased structural 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
This configuration effectively reduces on-resistance when a forward direction voltage is applied by increasing the Schottky junction area and forming a wider depletion layer to minimize leakage current.
Implementation Method 1
a width of the depletion layer blocking the leak current is not large, and thus there is a difficulty during a process in that an interval between the p+ regions is reduced
Data Source
AI summary
A schottky barrier diode may include a first n− type epitaxial layer disposed on a first surface of an n+ type silicon carbide substrate, a first p+ region disposed in the first n− type epitaxial layer, a second n type epitaxial layer disposed on the first n− type epitaxial layer and the first p+ region, a second p+ region disposed in the second n type epitaxial layer, a schottky electrode disposed on the second n type epitaxial layer and the second p+ region, and an ohmic electrode disposed on a second surface of the n+ type silicon carbide substrate, wherein the first p+ region and the second p+ region may be in contact with each other.