SiC Source Region Metallization for Low ON Resistance
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face challenges in reducing ON resistance due to its large bandgap and smaller electron affinity, making it difficult to find appropriate metallic materials that lower the barrier between the source region and the channel region, which is crucial for reducing parasitic resistance.
Innovation Solution
The introduction of elements like magnesium, calcium, strontium, and lanthanum into the carbon sites of the SiC substrate during ion implantation, followed by heat treatment, creates a metallized SiC source region with a work function matching the SiC's conduction band, effectively reducing the energy barrier and ON resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metallic materials are used to metallize the source region in SiC devices, then the parasitic resistance of the source region can be reduced, but it is difficult to find appropriate metallic materials with suitable work function due to SiC's large bandgap and smaller electron affinity
Solution Approach 1:
The patent changes the work function parameter of the source region by introducing metallic elements (Mg, Ca, Sr, Ba, Sc, Y, La, or lanthanoids) into the SiC source region. This modifies the electronic structure and work function of the source region to achieve better band alignment with the channel region, thereby reducing the energy barrier and parasitic resistance without requiring external metallic materials.
Solution Approach 2:
The patent creates a composite structure by combining SiC with metallic elements within the source region. This forms a SiC-based composite material that inherits the beneficial properties of SiC (wide bandgap, high thermal conductivity) while gaining the low work function characteristics of metallic elements, achieving both low parasitic resistance and compatibility with SiC's inherent properties.
2Reliability
If ion implantation and heat treatment are used to introduce metallic elements into SiC, then the energy barrier is reduced and ON resistance decreases, but the process complexity increases
Solution Approach 1:
The patent performs ion implantation of metallic elements into the source region before final device formation steps. This preliminary introduction of metallic elements allows subsequent heat treatment to effectively metallize the source region, reducing the energy barrier early in the process and simplifying later manufacturing steps.
Solution Approach 2:
The patent utilizes phase transition during heat treatment to transform the implanted metallic elements from a dispersed state into a metallized phase within the SiC source region. This phase transition enables effective metallization and work function modification, achieving low ON resistance through controlled thermal processing.
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 results in a semiconductor device with reduced ON resistance, improved cutoff characteristics, and enhanced reliability by eliminating carbon clusters and preventing film peeling, while maintaining low resistance and oxidation resistance.
Implementation Method 1
The introduction of elements like magnesium, calcium, strontium, and lanthanum into the carbon sites of the SiC substrate during ion implantation
Implementation Method 2
followed by heat treatment, creates a metallized SiC source region with a work function matching the SiC's conduction band
Data Source
AI summary
A semiconductor device according to an embodiment includes: a semiconductor substrate; an n-type SiC layer provided on one side of the semiconductor substrate; a p-type first SiC region provided in the n-type SiC layer; a metallic second SiC region provided in the p-type first SiC region, the second SiC region containing at least one element selected from the group of Mg, Ca, Sr, Ba, Sc, Y, La, and lanthanoid; a gate electrode; a gate insulating film provided between the gate electrode and the n-type SiC layer, the gate insulating film provided between the gate electrode and the first SiC region; a first electrode provided on the second SiC region; and a second electrode provided on a side of the semiconductor substrate opposite to the n-type SiC layer.