Silicon Carbide Substrate Surface Impurity Control for Low On-Resistance
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Solution Overview
Problem
The increase in on-resistance of semiconductor devices manufactured using silicon carbide substrates leads to reduced yield and efficiency, primarily due to impurities present on the substrate's surface, which affect the epitaxial growth layer formation.
Innovation Solution
A silicon carbide substrate with controlled surface impurity concentrations, specifically sulfur, oxygen, chlorine, carbon, metal, and sodium atoms within defined ranges, is developed to suppress the formation of high-resistivity layers and improve epitaxial growth quality, thereby reducing on-resistance and enhancing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfur atoms and oxygen atoms are introduced into the silicon carbide substrate surface within specific concentration ranges, then on-resistance is reduced and yield is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the concentration ranges of sulfur atoms (60×10¹⁰ to 2000×10¹⁰ atoms/cm²) and oxygen atoms (3 at% to 30 at%) on the silicon carbide substrate surface. This optimization of compositional parameters reduces on-resistance while improving device yield, demonstrating how controlled parameter variation resolves the technical contradiction between reliability improvement and manufacturing precision requirements
2Reliability
If the silicon carbide substrate resistivity is reduced in the thickness direction, then on-resistance decreases, but impurity introduction complexity increases
Solution Approach 1:
The patent applies local quality by introducing impurities specifically at the substrate surface region rather than uniformly throughout the bulk material. By concentrating sulfur and oxygen atoms at the surface within specific concentration ranges, the patent achieves reduced on-resistance through localized conductivity improvement while avoiding the complexity of bulk impurity introduction processes
3Reliability
If high concentration n-type dopant is introduced to reduce substrate resistivity, then on-resistance decreases, but manufacturing process complexity increases
Solution Approach 1:
The patent applies partial action by introducing impurities only at the substrate surface rather than throughout the entire substrate thickness. This surface-limited impurity introduction achieves the necessary resistivity reduction for low on-resistance while significantly simplifying the manufacturing process compared to bulk doping methods, as it requires less complex equipment and process control
Data Source
AI summary
A silicon carbide substrate capable of reducing on-resistance and improving yield of semiconductor devices is made of single-crystal silicon carbide, and sulfur atoms are present in one main surface at a ratio of not less than 60×1010 atoms/cm2 and not more than 2000×1010 atoms/cm2, and oxygen atoms are present in the one main surface at a ratio of not less than 3 at % and not more than 30 at %.