Epitaxial Wafer Roll-Off Structure for Rear Surface Flatness
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Solution Overview
Problem
Conventional methods for producing epitaxial wafers result in degraded flatness due to the attachment of epitaxial films on the outer peripheral portions of the rear surface, leading to increased production costs and quality issues such as scratches and contact marks from polishing, which necessitate a method to achieve high flatness without polishing the rear surface after forming the epitaxial film.
Innovation Solution
A method involving the intentional rolling off of the outer peripheral portion of the rear surface before forming the epitaxial film, allowing the epitaxial film to attach only to the rolled-off region, thereby maintaining high flatness without the need for post-film polishing of the rear surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxial growth is performed on a semiconductor wafer, then an epitaxial film is formed on the top surface, but an epitaxial film also attaches to the outer peripheral portion of the rear surface, degrading the flatness of the epitaxial wafer
Solution Approach 1:
The patent applies preliminary action by forming a roll-off structure on the rear surface of the semiconductor wafer before performing epitaxial growth. This roll-off structure pre-prevents the epitaxial film from attaching to the outer peripheral portion of the rear surface during the subsequent epitaxial growth process, thereby maintaining wafer flatness without requiring post-growth polishing operations.
2Manufacturing precision
If mirror-polishing is performed on the rear surface after forming an epitaxial film, then flatness is improved, but production cost increases and defects such as scratches and contact marks are generated
Solution Approach 1:
The patent applies preliminary anti-action by creating a roll-off structure on the rear surface before epitaxial growth that prevents the epitaxial film from attaching to the outer peripheral portion. This preliminary structural modification eliminates the need for post-growth mirror-polishing operations, thereby avoiding the generation of scratches and contact marks while maintaining production efficiency and reducing costs.
3Manufacturing precision
If the thickness of the epitaxial film on the top surface is increased, then the quality of the epitaxial wafer is improved, but the thickness of the epitaxial film on the outer peripheral portion of the rear surface increases accordingly, further degrading flatness
Solution Approach 1:
The patent applies preliminary action by forming a roll-off structure on the rear surface before epitaxial growth. This allows the top surface epitaxial film thickness to be increased for improved wafer quality without the corresponding increase in rear surface outer peripheral film thickness that would otherwise occur, thus maintaining flatness while enhancing product quality.
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 enables the production of epitaxial wafers with highly flat rear surfaces and reduced production costs by avoiding the defects associated with polishing, while maintaining high flatness even on the outer peripheral portions, as demonstrated by achieving an ESFQRmean value of 100 nm or less.
Implementation Method 1
An epitaxial film 50 is formed on a top surface 42a of this semiconductor wafer 40
Implementation Method 2
An epitaxial silicon wafer is advantageous in that a wafer heavily doped with dopants such as boron (B) or phosphorus (P) can be produced by typically vapor-growing
Data Source
AI summary
The present invention provides a method of producing an epitaxial wafer having a highly flat rear surface without polishing top and rear surfaces of the epitaxial wafer after forming an epitaxial film. A method of producing an epitaxial wafer 100 according to the present invention comprises a step of preparing a semiconductor wafer 10 having a beveled portion 11 formed on its end portion, a first surface 12b, a second surface 12a opposite to the first surface 12b, and edges 13b and 13a on both of the first surface 12b and the second surface 12a, the each edge 13a and 13b is boundary with the beveled portion 11; a step of processing of rolling off an outer peripheral portion 14 of the first surface 12b to form a roll-off region, the outer peripheral portion 14 is extending outward of the wafer from a predetermined position P inner than the position of the edge 13b on 12a the first surface 12b; and a step of forming a first epitaxial film 20 on the second surface 12a.