SiC Epitaxial Film Surface Flattening and Defect Removal
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Solution Overview
Problem
Conventional methods for manufacturing silicon carbide semiconductor devices fail to effectively remove defects in the epitaxial film not related to the primary substrate and often result in step bunching as a side effect, leading to issues like abnormal leak current and breakdown voltage failures.
Innovation Solution
A method involving chemical mechanical polishing to flatten the epitaxial film surface to 0.3 nm or less in arithmetic mean roughness, followed by thermal oxidation to form a sacrificial oxide, its removal using an aqueous hydrofluoric acid solution, and subsequent cleaning with deionized water to reduce defects and working damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the epitaxial film surface is flattened by chemical mechanical polishing to reduce defects, then manufacturing precision is improved, but step bunching occurs as a side effect
Solution Approach 1:
The patent applies preliminary action by performing chemical mechanical polishing on the epitaxial film before subsequent processing steps. This preliminary flattening removes surface irregularities and potential step bunching sites before the film undergoes further manufacturing processes, preventing defect propagation in later stages.
Solution Approach 2:
The patent employs parameter changes by carefully controlling the polishing parameters (pressure, speed, abrasive grain size, slurry composition) to achieve the desired surface flatness while minimizing step bunching. By optimizing these parameters, the process achieves Ra ≤ 0.3 nm without excessive step formation.
2Reliability
If conventional defect reduction methods are applied before epitaxial film formation, then substrate-related defects are reduced, but defects not depending on the primary substrate cannot be removed
Solution Approach 1:
The patent applies preliminary action by performing chemical mechanical polishing on the epitaxial film after its formation but before subsequent device fabrication steps. This timing allows removal of both substrate-related defects that propagated into the film and film-specific defects (such as particle contamination and growth-related irregularities) that would otherwise remain.
Solution Approach 2:
The patent introduces the epitaxial film itself as an intermediary object that can be selectively removed. By polishing the film surface and then selectively removing the polished layer, the process eliminates defects within the film while preserving the underlying substrate and desired film structure.
3Manufacturing precision
If the epitaxial film is heated to increase surface roughness for defect removal, then some defects are reduced, but the process complexity increases
Solution Approach 1:
The patent replaces thermal processing with a mechanical-chemical process (chemical mechanical polishing). Instead of heating the epitaxial film to alter surface roughness and remove defects, the invention uses controlled mechanical polishing with chemical assistance to achieve defect removal at room temperature, simplifying the overall process.
Solution Approach 2:
The patent changes the fundamental processing parameter from temperature (thermal treatment) to mechanical/chemical parameters (polishing pressure, speed, abrasive characteristics). This parameter substitution achieves defect removal through a different mechanism that avoids the complexity of thermal process control while maintaining effectiveness.
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 significantly reduces defects in the epitaxial film, enhancing the reliability and electrical properties of silicon carbide semiconductor devices by minimizing surface roughness and removing process-induced damage, resulting in improved yield and performance.
Implementation Method 1
flattening a surface of the epitaxial film by using chemical mechanical polishing up to 0.3 nm or less in arithmetic mean roughness Ra
Implementation Method 2
oxidizing the surface of the epitaxial film thermally to form a sacrificial oxide
Implementation Method 3
removing the sacrificial oxide
Data Source
AI summary
A method, for manufacturing a silicon carbide semiconductor device, includes: forming a silicon carbide epitaxial film on a silicon carbide substrate; flattening a surface of the epitaxial film by using chemical mechanical polishing such that the surface of the epitaxial film has an arithmetic mean roughness Ra of 0.3 nm or less; thermally oxidizing the surface of the epitaxial film to form a sacrificial oxide; removing the sacrificial oxide; and cleaning, by using deionized water, a surface of the epitaxial film exposed by the removing of the sacrificial oxide.