SiC Schottky Contact Structure for High-Temperature Metallization
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Solution Overview
Problem
Existing manufacturing methods for silicon carbide (SiC) power semiconductor devices face challenges in achieving thermal stability and simultaneous formation of ohmic and Schottky barrier contacts, leading to susceptibility to adverse conditions during high-temperature processing.
Innovation Solution
Incorporating a carbon group interlayer between the metal layer and the SiC structure, which allows for improved thermal stability of the Schottky barrier contact and enables the simultaneous formation of ohmic and Schottky barrier contacts at high temperatures, reducing resistance to adverse conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a two-step metallization process is used to form ohmic and Schottky contacts separately, then contact formation is achieved, but manufacturing complexity and processing time increase
Solution Approach 1:
The patent combines the formation of ohmic contacts and Schottky barrier contacts into a single simultaneous metallization step. By depositing a multi-layer metal structure that differentially forms ohmic contacts on one surface and Schottky contacts on another surface in one process, the manufacturing complexity is reduced while maintaining contact formation effectiveness.
Solution Approach 2:
The metal layer structure is designed to serve multiple functions simultaneously: it forms both ohmic and Schottky contacts in a single deposition process, and the intermediate carbon group interlayer serves both as a diffusion barrier and as a template for selective contact formation, achieving multi-functionality that simplifies the overall manufacturing process.
2Reliability
If high-temperature processing is applied to form ohmic contacts, then contact resistance is reduced, but Schottky barrier contacts degrade due to thermal instability
Solution Approach 1:
The carbon group interlayer acts as an intermediary between the metal layers and the SiC substrate. This intermediate layer has high thermal stability and serves as a diffusion barrier, allowing the structure to withstand high-temperature processing needed for ohmic contact formation without degrading the Schottky barrier contact properties. The interlayer mediates the thermal stress and prevents direct thermal damage to the Schottky interface.
Solution Approach 2:
The patent employs a composite metal layer structure consisting of multiple metal layers with a carbon group interlayer in between. This composite structure combines materials with different thermal properties: the first metal layer is optimized for ohmic contact formation at high temperature, while the second metal layer forms the Schottky barrier, and the carbon interlayer provides thermal stability. The composite nature allows simultaneous achievement of low contact resistance and thermal stability.
3Temperature
If thermal stability is improved by adding a carbon group interlayer, then processing temperature can be increased, but device structure complexity increases
Solution Approach 1:
The carbon group interlayer is strategically placed only at specific locations where thermal stability is most needed - namely at the Schottky contact interface and as a diffusion barrier. The interlayer is not uniformly present throughout the entire device structure but is localized to critical regions, thereby providing thermal stability benefits while minimizing the overall increase in 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
The solution enhances the thermal stability and manufacturing efficiency of SiC power semiconductor devices, such as Schottky barrier diodes and vertical FETs, by maintaining low leakage current, forward voltage drop, and reverse recovery time, while allowing for high-temperature processing steps without degradation.
Implementation Method 1
the graphene layer is used for blocking the interpenetration between silicon carbide atoms of the silicon carbide epitaxial layer and metal atoms of the Schottky metal layer, thereby reducing the leakage current
Implementation Method 2
a Schottky metal layer and a graphene layer arranged between the silicon carbide epitaxial layer and the Schottky metal layer
Implementation Method 3
a low contact resistance, ohmic contact is deposited on a SiC substrate and then sintered at a relatively high temperature of 900 to 1000° C.
Data Source
AI summary
The present disclosure relates to a power semiconductor device (100) comprising a silicon carbide semiconductor. SiC. structure (110) comprising a SiC epilayer (112), at least one ohmic contact (120) formed on a first main surface (114) of the SiC structure (110), and at least Schottky barrier contact (130) formed on a second main surface (116) of the SiC structure (110). The at least one Schottky barrier contact (130) comprises a metal layer (136) and a carbon group interlayer (134) arranged between the metal layer (136) and the second main surface (116) of the SiC structure (110). 15 The present disclosure relates to a Schottky barrier diode (400). a vertical field effect transistor, such as a power MOSFET (500), and a method for manufacturing a power semiconductor device (100).