Compound Semiconductor Surface Layer Chloride Oxide Control
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Solution Overview
Problem
The existing methods for preparing semiconductor substrates result in high electric resistance at the interface between the epitaxial layer and the substrate, leading to degraded device characteristics due to silicon accumulation, which hinders the achievement of good yield and performance in high-speed and optical communication devices.
Innovation Solution
A Group III nitride compound semiconductor substrate with a surface layer containing specific concentrations of chloride and oxide, formed through dry etching with a chlorine-based gas, reduces silicon accumulation at the interface, thereby lowering the electric resistance. The surface layer has a controlled composition and roughness to facilitate epitaxial growth with improved morphology and crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mirror polishing is performed on the semiconductor substrate surface, then surface smoothness is improved, but silicon accumulation occurs at the interface leading to high electric resistance
Solution Approach 1:
The invention changes the chemical composition parameters of the surface layer by controlling the concentration of chloride (not less than 200×10^10 atoms/cm²) and oxide (5.0-12.0 at%) to prevent silicon accumulation while maintaining surface smoothness, thereby resolving the contradiction between surface quality and electrical properties
Solution Approach 2:
The surface layer acts as an intermediary between the substrate and the epitaxial layer, containing specific concentrations of chloride and oxide that prevent silicon from migrating to the interface, thus mediating the conflict between surface preparation and electrical resistance
2Reliability
If dry etching is performed to remove silicon, then electric resistance is reduced, but surface roughness may increase
Solution Approach 1:
The invention optimizes the parameters of the surface layer composition (chloride and oxide concentrations) and surface roughness (RMS ≤ 3 nm) to achieve both low electric resistance and acceptable surface quality for epitaxial growth
Solution Approach 2:
The invention replaces mechanical polishing with chemical etching using chlorine-based gas to remove silicon, substituting a mechanical process that causes silicon accumulation with a chemical process that achieves silicon removal while controlling surface morphology
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 effectively reduces the electric resistance at the interface, enhancing the electrical properties and yield of semiconductor devices by controlling the chloride, oxide, and silicon concentrations, and surface roughness, leading to better device performance.
Implementation Method 1
dry etching with a chlorine-based gas
Implementation Method 2
formed through dry etching with a chlorine-based gas
Data Source
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AI summary
A compound semiconductor substrate 10 according to the present invention is comprised of a Group III nitride and has a surface layer 12 containing a chloride of not less than 200×1010 atoms/cm2 and not more than 12000× 1010 atoms/cm2 in terms of C1 and an oxide of not less than 3.0 at% and not more than 15.0 at% in terms of O, at a surface. The inventors conducted elaborate research and newly discovered that when the surface layer 12 at the surface of the compound semiconductor substrate 10 contained the chloride of not less than 200 × 1010 atoms/cm2 and not more than 12000x 1010 atoms/cm2 in terms of Cl and the oxide of not less than 3.0 at% and not more than 15.0 at% in terms of O, Si was reduced at an interface between the compound semiconductor substrate 10 and an epitaxial layer 14 formed thereon and, as a result, the electric resistance at the interface was reduced.