MoS2 Contact Structure for SiC MPS Diodes Without Nickel Residues
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Solution Overview
Problem
The existing manufacturing processes for SiC-based MPS devices face issues with unwanted reactions between Nickel and the Silicon mask, leading to irregular regions and potential short circuits, which compromise the device's performance and reliability.
Innovation Solution
The introduction of a semiconductor layer made of Molybdenum Sulfide (MoS2) that is selectively doped to form ohmic and Schottky contacts, replacing traditional Nickel-based contacts and addressing the issues of irregular regions and short circuits by modifying the conductivity and potential barrier of the MoS2 layer through doping and layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional Nickel-based contacts are used in the manufacturing process, then ohmic contacts can be formed, but unwanted reactions occur between Nickel and the Silicon mask leading to irregular regions and potential short circuits
Solution Approach 1:
A semiconductor layer is introduced as an intermediary between the metal contact and the drift layer. This intermediate layer prevents direct contact and unwanted reactions between the metal (Nickel or alternative materials) and the Silicon mask or drift layer, thereby eliminating the formation of irregular regions and potential short circuits while still enabling effective electrical contact.
Solution Approach 2:
The problematic direct interaction between Nickel and Silicon mask is extracted/removed from the system by inserting a semiconductor layer in between. This separates the metal contact function from the mask layer, preventing the harmful chemical reaction and irregular region formation that would otherwise occur.
2Reliability
If the semiconductor layer is selectively doped to form ohmic and Schottky contacts, then contact performance is improved, but the manufacturing process complexity increases
Solution Approach 1:
The semiconductor layer is selectively doped with different dopant concentrations in different regions. Areas requiring ohmic contacts receive heavy doping to reduce contact resistance, while areas requiring Schottky contacts maintain lighter doping to preserve the barrier properties. This localized differentiation optimizes contact performance for each specific function.
Solution Approach 2:
The doping concentration parameter of the semiconductor layer is varied spatially to achieve different contact characteristics. By changing the dopant concentration from high to low across different regions, the patent creates both ohmic and Schottky contact regions within the same semiconductor layer, optimizing electrical performance.
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 maximizes the 'IFSM ruggedness' of SiC MPS diodes, simplifies the manufacturing process, and eliminates the problems associated with Nickel residues, enhancing the overall performance and reliability of the devices.
Implementation Method 1
The semiconductor layer is selectively doped in order to selectively modify the conductivity of the semiconductor layer. The semiconductor layer thus has doped regions with a first type of conductivity at respective JB elements, and regions with a second type of conductivity at surface portions of the drift layer
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
Merged-PiN-Schottky, MPS, device (50) comprising: a solid body (52, 53) having a first electrical conductivity (N); an implanted region (59) extending into the solid body (52, 53) facing a front side (52a) of the solid body (52, 53), having a second electrical conductivity (P) opposite to the first electrical conductivity (N); and a semiconductor layer (61) extending on the front side (52a), of a material which is a transition metal dichalcogenide, TMD. A first region (61') of the semiconductor layer (61) has the second electrical conductivity (P) and extends in electrical contact with the implanted region (59), and a second region (61") of the semiconductor layer (61) has the first electrical conductivity (N) and extends adjacent to the first region (61') and in electrical contact with a respective surface portion of the front side (52a) having the first electrical conductivity (N).