SiC Drift Layer Irradiation for Stacking Fault Suppression
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face conduction deterioration and increased ON-resistance due to basal plane dislocations, which are exacerbated by the extension of stacking faults caused by minority carrier recombination, and existing methods like lifetime killers often result in uneven distribution and increased manufacturing costs.
Innovation Solution
A SiC semiconductor device configuration that includes a drift layer, a base region, a main region, an insulated gate electrode structure, and a lifetime killer region formed by irradiating the top surface of the drift layer with protons or helium ions before forming the gate insulating film, ensuring the lifetime killer region covers the bottom surface of the drift layer to recombine minority carriers effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a recombination promotion layer of n+-type is arranged between the substrate and the drift layer to recombine holes, then the forward characteristics of the internal diode are improved, but the manufacturing cost increases due to the required thickness of about 10 micrometers
Solution Approach 1:
The patent changes the key parameter from layer thickness to ion irradiation dose and energy. Instead of requiring a thick n+-type layer (10 micrometers), the invention uses proton or helium ion irradiation with controlled dose (1×10^12 to 1×10^14 ions/cm²) and energy (1 MeV to 10 MeV) to create the same recombination effect in a much thinner region, thereby reducing manufacturing cost while maintaining diode performance.
Solution Approach 2:
The patent replaces the mechanical/structural approach (adding a thick doped layer) with a physical irradiation approach (ion bombardment). The ion irradiation creates point defects and displacement damage that serve as recombination centers, substituting the need for a thick physical layer with a radiation-induced structural modification.
2Reliability
If the lifetime killer irradiation is made from the rear surface side of the SiC substrate, then the gate insulating film is protected, but the lifetime killer is distributed ununiformly in the drift layer causing variation in ON-resistance
Solution Approach 1:
The patent inverts the irradiation direction from the conventional rear-surface-side approach to the front-surface-side approach. By irradiating through the drift layer from the front surface, the patent achieves uniform distribution of the lifetime killer effect throughout the drift layer thickness, while still protecting the gate insulating film by performing irradiation before gate formation.
Solution Approach 2:
The patent performs the lifetime killer irradiation as a preliminary step before forming the gate insulating film and other surface structures. This timing ensures that the irradiation effect is uniformly distributed throughout the drift layer before subsequent processing steps, preventing any potential damage to the gate insulating film while achieving uniform carrier lifetime reduction.
3Reliability
If protons or helium ions are irradiated to form a lifetime killer region, then minority carrier recombination is enhanced and stacking fault extension is suppressed, but the ON-resistance increases when the drift layer is irradiated
Solution Approach 1:
The patent applies local quality by concentrating the ion irradiation effect specifically at the interface region between the drift layer and the substrate, rather than uniformly throughout the entire drift layer. By controlling the ion energy and dose, the lifetime killer effect is localized to where it is most needed (at the dislocation-prone interface), suppressing stacking faults without significantly increasing the ON-resistance of the bulk drift layer.
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 configuration effectively reduces conduction deterioration and ON-resistance variation by accurately forming a lifetime killer region that recombines minority carriers, suppressing the extension of stacking faults and maintaining device performance without affecting the gate insulating film or increasing manufacturing costs.
Implementation Method 1
a lifetime killer region formed by irradiating the top surface of the drift layer with protons or helium ions before forming the gate insulating film
Implementation Method 2
recombine minority carriers effectively
Data Source
AI summary
A manufacturing method of a silicon carbide semiconductor device includes: epitaxially growing a drift layer of a first conductivity-type on a silicon carbide substrate of the first conductivity-type; forming a base region of a second conductivity-type on the drift layer; forming a main region of the first conductivity-type on the drift layer so as to be in contact with the base region; forming a gate insulating film so as to be in contact with the base region and the main region; forming a gate electrode so as to be in contact with the base region and the main region with the gate insulating film interposed; and forming a lifetime killer region at a depth covering a bottom surface of the drift layer by irradiating the top surface side of the drift layer with a lifetime killer after epitaxially growing the drift layer and before forming the gate insulating film.