SiC Ohmic Electrode with Ni-P Silicide for Low Resistance
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Solution Overview
Problem
Existing silicon carbide (SiC) semiconductor devices face challenges in achieving desired ohmic characteristics and sufficient adhesion strength between the SiC substrate and the electrode, particularly when forming ohmic electrodes on the rear surface after grinding, which requires preventing thermal damage and avoiding expensive ion implantation processes.
Innovation Solution
A silicon carbide semiconductor device with an ohmic electrode made of Ni containing 0.1 wt% to 15 wt% P, forming Ni silicide including Ni5P2, which is achieved through laser annealing of a Ni-P layer on the SiC substrate, providing low contact resistance and high adhesion strength without ion implantation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation process is used to form ohmic electrode, then ohmic characteristics are improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the material parameters by using Ni-P alloy with specific phosphorus content (3-15 wt%) instead of pure Ni, and controls the silicide layer composition to contain Ni5P2 phase. This material parameter change enables achieving good ohmic characteristics without requiring expensive ion implantation process
Solution Approach 2:
The patent replaces the expensive ion implantation process with a simpler, more cost-effective laser annealing process. The laser annealing method uses a cheaper process that can achieve the desired ohmic characteristics through controlled heating and silicide formation, eliminating the need for costly ion implantation equipment and processing
2Object-affected harmful factors
If laser annealing is used to form ohmic electrode on ground rear surface, then thermal damage to front surface is prevented, but adhesion strength is insufficient
Solution Approach 1:
The patent uses a composite electrode structure consisting of Ni-P alloy metal layer combined with silicide layer containing Ni5P2 phase. This composite material structure provides both low contact resistance and high adhesion strength to the SiC substrate, overcoming the limitation of using simple Ni silicide formed by conventional laser annealing
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating phosphorus into the Ni electrode material (3-15 wt% P content). This compositional change modifies the laser annealing behavior and silicide formation characteristics, enabling the formation of Ni5P2 phase that significantly improves adhesion strength while maintaining the localized heating advantage of laser annealing
3Reliability
If Ni silicide layer is formed by laser annealing, then contact resistance is reduced, but adhesion strength between SiC and electrode is insufficient
Solution Approach 1:
The patent creates a composite electrode system where Ni-P alloy reacts with SiC to form a silicide layer containing both NiSi and Ni5P2 phases. The Ni5P2 phase acts as an intermetallic compound that provides strong bonding to the SiC substrate, while the NiSi phase provides low contact resistance. This composite silicide structure simultaneously achieves both low contact resistance and high adhesion strength
Solution Approach 2:
The patent modifies the electrode material composition by adding phosphorus to Ni (creating Ni-P alloy with 3-15 wt% P). During laser annealing, this compositional change enables the formation of Ni5P2 phase in the silicide layer, which has superior adhesion properties compared to conventional NiSi alone, while maintaining low contact resistance characteristics
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 approach results in stable, low contact resistance and high adhesion strength between the SiC substrate and the electrode, while minimizing thermal damage and eliminating the need for costly ion implantation processes, thus enhancing the manufacturing efficiency and performance of SiC semiconductor devices.
Implementation Method 1
irradiating the metal thin film with laser light and reacting the Ni with Si in the silicon carbide to generate Ni silicide
Implementation Method 2
laser annealing technique capable of performing local heating may be used
Implementation Method 3
reacting the Ni with Si in the silicon carbide to generate Ni silicide
Data Source
AI summary
A silicon carbide semiconductor device includes a silicon carbide semiconductor substrate having a front surface and a rear surface, and an ohmic electrode in ohmic contact with silicon carbide of at least one of the front surface or the rear surface of the silicon carbide semiconductor substrate. The ohmic electrode is made of Ni containing 0.1 wt % or more and 15 wt % or less of P as an impurity. The ohmic electrode contains Ni silicide including NiSi. The ohmic electrode further contains Ni5P2 in the Ni silicide. A method for manufacturing the silicon carbide semiconductor device includes forming a metal thin film on the silicon carbide that is to be in ohmic contact with the ohmic electrode, and forming the ohmic electrode by laser annealing that includes irradiating the metal thin film with laser light and reacting the Ni with Si in the silicon carbide to generate Ni silicide.