SiC Schottky Barrier Diode Electrode Segmentation
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Solution Overview
Problem
Conventional SiC Schottky barrier diodes face challenges in achieving both low forward threshold voltage and reverse leakage current, with materials like nickel increasing threshold voltage but suppressing leakage current, and titanium silicide decreasing barrier height but increasing leakage current, making it difficult to stabilize operation at varying temperatures without significant series resistance and leakage current issues.
Innovation Solution
A semiconductor device structure with a Schottky junction and junction barriers on an SiC substrate, where the barrier height is 1 eV or less, and specific geometric relationships between junction barriers and edge termination regions are maintained to control reverse leakage current and ensure stable operation, including a depth ratio of junction barriers to edge termination regions (d1/d2 >= 1) and space-to-width ratios (s/d1 <= 0.6 and s/(w+s) <= 0.33) to manage on-resistance and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If nickel is used as electrode material to increase Schottky barrier height, then reverse leakage current is suppressed, but forward threshold voltage increases
Solution Approach 1:
The electrode structure is segmented into multiple layers (first electrode layer, second electrode layer, third electrode layer) with different materials and functions. The first layer (TiSi2) provides low barrier height for low forward voltage, the second layer (Ni) provides high barrier height for low reverse leakage, and the third layer (Pt) provides protection. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between forward voltage and reverse leakage current.
Solution Approach 2:
The electrode uses a composite multi-layer structure combining different materials (TiSi2, Ni, Pt) with complementary properties. TiSi2 contributes low work function for low forward voltage drop, Ni contributes high work function for low reverse leakage current, and Pt contributes chemical stability. The composite structure achieves performance that cannot be obtained with a single material.
2Loss of energy
If titanium silicide is used as electrode material to decrease Schottky barrier height, then forward threshold voltage decreases, but reverse leakage current increases
Solution Approach 1:
The electrode is divided into functional segments where TiSi2 (first layer) handles the forward conduction with low barrier height, while Ni (second layer) handles reverse blocking with high barrier height. This segmentation allows TiSi2 to minimize forward voltage loss without being penalized by its high reverse leakage, as the Ni layer suppresses reverse leakage independently.
Solution Approach 2:
The composite electrode structure combines TiSi2's low work function (4.6 eV) for efficient forward conduction with Ni's high work function (5.0 eV) for effective reverse blocking. The combination creates an electrode that simultaneously achieves low forward threshold voltage and low reverse leakage current, overcoming the limitations of individual materials.
3Object-generated harmful factors
If a semiconductor region with different conductivity type is formed on the surface to reduce leakage current, then reverse leakage current is suppressed, but series resistance increases and work area of drift layer is reduced
Solution Approach 1:
Instead of adding a semiconductor region in the planar direction that would reduce the drift layer work area, the solution adds depth in the vertical dimension by creating a multi-layer electrode structure. The third electrode layer (Pt) is positioned at the deepest level, providing leakage suppression through its high work function and chemical stability without occupying lateral space that would reduce the drift layer's effective area, thus maintaining low series resistance.
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 proposed structure effectively reduces reverse leakage current and maintains low on-resistance, ensuring stable operation at high temperatures and achieving a breakdown voltage determined by avalanche domination, with negligible increase in on-resistance and controlled leakage current, even at elevated temperatures.
Implementation Method 1
a Schottky junction formed by joining a first electrode layer to the semiconductor layer, a barrier height of the Schottky junction being 1 eV or less
Implementation Method 2
the reverse leakage current is reduced to enhance the breakdown voltage by a depletion layer which is formed on the side of a first semiconductor region (2) by a junction barrier (4)
Implementation Method 3
achieving a breakdown voltage determined by avalanche domination
Data Source
AI summary
A semiconductor device includes a first-conductivity-type SiC substrate, a first-conductivity-type SiC semiconductor layer formed on the substrate, whose impurity concentration is lower than that of the substrate, a first electrode formed on the semiconductor layer and forming a Schottky junction with the semiconductor layer, a barrier height of the Schottky junction being 1 eV or less, plural second-conductivity-type junction barriers formed to contact the first electrode and each having a depth d1 from an upper surface of the semiconductor layer, a width w, and a space s between adjacent ones of the junction barriers, a second-conductivity-type edge termination region formed outside the junction barriers to contact the first electrode and having a depth d2 from the upper surface of the semiconductor layer, and a second electrode formed on the second surface of the substrate, wherein following relations are satisfied d1/d2≧1, s/d1≦0.6, and s/(w+s)≦0.33.