SiC Epitaxial Substrate Defect Control via CMP
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Solution Overview
Problem
Existing silicon carbide semiconductor devices face challenges in manufacturing due to the formation of annular defects caused by threading dislocations during the polishing process, which affect the reliability and surface quality of the epitaxial substrates.
Innovation Solution
A silicon carbide epitaxial substrate with a 4H polytype and a {0001} plane or a plane inclined by less than 5° is used, featuring arc-shaped or annular basal plane dislocations and threading dislocations, with a specific distribution and density of defects to minimize annular defects, and a method involving mechanical and chemical mechanical polishing to control defect formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If mechanical polishing is performed on silicon carbide substrate to improve surface quality, then surface roughness is reduced, but annular defects are formed due to threading dislocations
Solution Approach 1:
The patent applies chemical mechanical polishing instead of conventional mechanical polishing, changing the polishing mechanism from purely mechanical to a combination of chemical and mechanical actions. This parameter change in the polishing process enables effective removal of annular defects while maintaining surface quality, resolving the contradiction between surface quality improvement and defect formation
Solution Approach 2:
The patent introduces a chemical component as an intermediary in the polishing process. The chemical agent interacts with the threading dislocations and annular defects, facilitating their removal during polishing. This intermediary substance enables the polishing process to address defects that would otherwise be difficult to remove mechanically
2Productivity
If conventional polishing methods are used to reduce surface roughness, then manufacturing efficiency is improved, but reliability decreases due to scratch formation
Solution Approach 1:
The patent changes the polishing method from mechanical to chemical mechanical, fundamentally altering the material removal mechanism. This parameter change enables the process to achieve both high manufacturing efficiency and high reliability by eliminating scratch formation while maintaining productive throughput
Solution Approach 2:
The patent replaces the purely mechanical polishing system with a chemical mechanical polishing system. By substituting mechanical action with a combination of chemical and mechanical actions, the process achieves superior surface quality and device reliability without sacrificing manufacturing efficiency
3Stability of the object's composition
If threading dislocations are present in the epitaxial film to maintain area density above 50 cm−2, then crystal structure is stabilized, but annular defect density increases
Solution Approach 1:
The patent converts the harmful effect of threading dislocations (which generate annular defects) into a beneficial process feature. By using chemical mechanical polishing, the threading dislocations serve as indicators for targeted defect removal, allowing the process to selectively eliminate annular defects while preserving the necessary threading dislocation density for crystal stability
Solution Approach 2:
The patent changes the defect removal mechanism through chemical mechanical polishing, enabling selective removal of annular defects while preserving threading dislocations. This parameter change in the polishing process allows simultaneous maintenance of crystal structure stability and reduction of harmful annular defect density
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 reduces the area density ratio of annular defects to threading dislocations, enhancing the reliability and surface quality of silicon carbide semiconductor devices by minimizing scratch formation and maintaining a low surface roughness.
Implementation Method 1
a silicon carbide epitaxial film and a silicon carbide substrate. The silicon carbide epitaxial film is on the silicon carbide substrate. The silicon carbide substrate and the silicon carbide epitaxial film have a polytype of 4H
Implementation Method 2
a method involving mechanical and chemical mechanical polishing to control defect formation
Data Source
AI summary
A silicon carbide epitaxial film has a plurality of arc-shaped or annular basal plane dislocations and a plurality of threading dislocations. The plurality of threading dislocations have a first threading dislocation which is surrounded by the plurality of basal plane dislocations and a second threading dislocation which is not surrounded by the plurality of basal plane dislocations, when viewed from a direction perpendicular to a main surface. The plurality of basal plane dislocations and the first threading dislocation constitute an annular defect. An area density of the plurality of threading dislocations in the main surface is more than or equal to 50 cm−2. A value obtained by dividing an area density of the annular defect when viewed from the direction perpendicular to the main surface by the area density of the plurality of threading dislocations in the main surface is more than or equal to 0.00002 and less than or equal to 0.004.