Semiconductor Substrate Bevel Finishing for Defect-Safe Epitaxy
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Solution Overview
Problem
High surface roughness of sloped portions on semiconductor substrates leads to defects and failures in epitaxial layers, particularly in reclaimed substrates, resulting in increased defect density and reduced reliability of power semiconductor devices.
Innovation Solution
A manufacturing method that includes polishing and grinding the sloped portions to reduce their surface roughness, ensuring it is lower than 200 nm and further polished to less than 1 nm, thereby improving the flatness and reducing defects in the epitaxial layers formed on reclaimed substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If beveling portions are formed at the edge of the substrate to suppress cracking and chipping, then the mechanical strength and reliability of the substrate is improved, but the surface roughness of the sloped portions increases leading to defects in epitaxial layers
Solution Approach 1:
The patent applies preliminary action by performing polishing and grinding treatments on the sloped portions before forming the epitaxial layer. This pre-treatment removes the rough surface created by beveling, creating a smooth surface that prevents defects in the subsequent epitaxial growth process while maintaining the crack-prevention function of the beveled edges
Solution Approach 2:
The patent applies local quality by treating only the sloped portions (beveling areas) with polishing and grinding, while leaving the main substrate surfaces unchanged. This localized treatment reduces surface roughness specifically where it causes problems (at the edges) without affecting the overall substrate properties or requiring complete reprocessing of the entire substrate
2Ease of manufacture
If simple beveling is performed to reduce edge defects, then the processing complexity is reduced, but the defect density in epitaxial layers increases due to high surface roughness
Solution Approach 1:
The patent performs polishing and grinding as preliminary treatments before epitaxial growth to create a smooth surface on the sloped portions. This preliminary surface preparation ensures that when the epitaxial layer is subsequently formed, it grows uniformly without defects caused by surface roughness, thereby reducing defect density while maintaining a relatively simple overall process flow
3Productivity
If the surface roughness of sloped portions is high, then the manufacturing process is simpler and faster, but the reliability of power semiconductor devices is reduced due to increased defect density
Solution Approach 1:
The patent changes the surface finish parameter of the sloped portions by applying polishing and grinding treatments. This parameter change reduces the surface roughness from a high-roughness state (which would be faster to produce) to a low-roughness state (which ensures reliability), thereby achieving high device reliability without significantly impacting manufacturing productivity
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 method effectively suppresses the occurrence of defects and failures in epitaxial layers, enhancing the reliability and reducing manufacturing costs of semiconductor devices by improving the surface roughness of sloped portions and stabilizing the epitaxial growth process.
Implementation Method 1
polishing the second main surface... grinding the first sloped portion
Implementation Method 2
forming an epitaxial layer on the first main surface and the first sloped portion
Data Source
AI summary
A method of manufacturing a semiconductor substrate includes (a) preparing a substrate having a front surface, a back surface located on an opposite side of the front surface, a first sloped portion connected to the front surface, and a second sloped portion connected to the back surface, (b) forming an epitaxial layer on the front surface and the first sloped portion, (c) after the (b), polishing the back surface, and (d) after the (c), grinding the first sloped portion.