SiC Ohmic Contact Formation Using a Laser-Induced 3C-SiC Layer
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Solution Overview
Problem
The creation of reliable Ohmic contacts on silicon carbide (SiC) semiconductor substrates is challenging due to issues with adhesion failures caused by carbon byproducts under high temperature conditions, particularly for 4H—SiC substrates, which affects the stability and performance of semiconductor devices.
Innovation Solution
A method involving thermal annealing with a laser beam to generate a 3C—SiC layer on the substrate surface, followed by deposition of a contact material, which reduces contact resistance and eliminates the need for additional doping or silicidation processes, thereby enhancing adhesion and reliability of the Ohmic contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni is used as contact material to make Ohmic contact with 4H-SiC substrate, then contact resistance is reduced, but carbon byproducts (NiSi, carbon clusters, thin carbon films) are generated at the interface causing adhesion failures
Solution Approach 1:
The patent introduces a TiN intermediate layer between the Ni contact material and the 4H-SiC substrate. This intermediary layer prevents direct reaction between Ni and SiC, eliminating carbon byproduct formation while maintaining low contact resistance through the TiN-Ni-SiC contact structure.
Solution Approach 2:
The patent extracts the harmful carbon byproduct formation mechanism by separating the contact material (Ni) from direct contact with the substrate (4H-SiC). The TiN layer acts as a barrier that removes the source of carbon contamination while preserving the electrical contact function.
2Temperature
If conventional Ni contact process is used, then Ohmic contact is achieved, but adhesion failures occur under high temperature conditions causing peeling off of metallization
Solution Approach 1:
The TiN intermediate layer serves as a thermally stable intermediary that prevents direct interaction between Ni and SiC at high temperatures. This barrier layer maintains structural integrity and prevents adhesion failures even under elevated temperature conditions during device operation.
Solution Approach 2:
The patent creates a composite contact structure consisting of TiN and Ni layers with distinct functional properties. The TiN layer provides thermal stability and prevents carbon formation, while the Ni layer provides low contact resistance, creating a composite system that outperforms conventional single-layer contacts at high temperatures.
3Reliability
If additional doping or silicidation processes are used to improve contact, then contact resistance is reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the need for additional doping or silicidation processes by using the TiN-Ni contact structure. The TiN layer inherently provides good electrical contact properties, eliminating the requirement for complex additional processing steps while achieving low contact resistance.
Solution Approach 2:
The TiN layer performs multiple functions simultaneously: it serves as an adhesion layer, a diffusion barrier, and a contact resistance reduction layer. This multi-functionality eliminates the need for separate doping or silicidation processes, simplifying the manufacturing workflow while maintaining contact 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 method enables the formation of efficient, cost-sensitive Ohmic contacts with improved reliability and reduced contact resistance, ensuring stability and high performance of SiC-based semiconductor devices, even under harsh conditions.
Implementation Method 1
irradiating a surface area of the 4H—SiC semiconductor substrate with a first thermal annealing laser beam, thereby generating a phase separation of the surface area comprising at least a 3C—SiC layer
Implementation Method 2
irradiating a surface area of the 4H—SiC semiconductor substrate with a first thermal annealing laser beam
Implementation Method 3
generating a phase separation of the surface area comprising at least a 3C—SiC layer
Implementation Method 4
depositing a contact material onto the 3C—SiC layer to form a contact layer on the semiconductor substrate
Data Source
AI summary
The present disclosure generally relates to a method of manufacturing a contact on a silicon carbide semiconductor substrate wherein the method comprises providing a 4H—SiC semiconductor substrate, irradiating a surface area of the 4H—SiC semiconductor substrate with a first thermal annealing laser beam, thereby generating a phase separation of the surface area comprising at least a 3C—SiC layer, and depositing a contact material onto the 3C—SiC layer to form a contact layer on the semiconductor substrate. The disclosure further relates to a silicon carbide semiconductor device with an Ohmic contact comprising a 4H—SiC semiconductor substrate, a 3C—SiC layer, and a contact layer directly in contact with the 3C—SiC layer at the semiconductor surface.