SiC-Coated Susceptor with Beveled Edge for Epitaxial Growth
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Solution Overview
Problem
Conventional susceptors used in semiconductor wafer epitaxial growth processes face issues such as surface cutting, crack generation, wafer instability, and non-uniform heat treatment due to the hardness of SiC coatings, leading to short lifetimes and epitaxial layer uniformity problems.
Innovation Solution
A susceptor design with a SiC grain growth surface portion left unpolished on the outer circumference of recesses, featuring a ring-shaped SiC crystal growth surface with specific surface roughness and a beveled wafer edge to prevent contact with susceptor apexes, ensuring stable wafer mounting and uniform heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the SiC coated surface is polished to reduce surface roughness, then the wafer surface cutting is prevented, but stress concentration occurs during polishing causing fine cracks in the film
Solution Approach 1:
The patent applies different surface treatments to different regions of the susceptor. The wafer contact surface is polished to prevent cutting, while the outer circumference portion is left unpolished or lightly treated to avoid stress concentration and cracking. This localized differentiation resolves the contradiction by optimizing each region for its specific function.
2Object-affected harmful factors
If the entire recess surface is polished to prevent wafer cutting, then the wafer mounting surface is improved, but gas remains at contact interface causing wafer to slide and come off
Solution Approach 1:
The patent creates different surface characteristics in different regions: the wafer contact surface is polished for smooth contact, while the outer circumference portion has a rougher, unpolished surface that provides gas release pathways and prevents wafer sliding. This local differentiation simultaneously achieves cutting prevention and mounting stability.
3Ease of manufacture
If the outer circumference portion is subjected to ordinary CVD-SiC coating or mirror polishing, then the susceptor manufacturing is simplified, but gas flow is disturbed causing non-uniform epitaxial layer and impurity agglomeration
Solution Approach 1:
The patent specifies a particular surface treatment for the outer circumference portion that differs from conventional approaches. By leaving this region unpolished or applying a specific treatment, the patent maintains manufacturing simplicity while ensuring proper gas flow patterns and preventing impurity agglomeration, thus achieving both ease of manufacture and epitaxial layer uniformity.
4Productivity
If the susceptor is used repeatedly with conventional designs, then production efficiency is maintained, but cracks generate at lower portion of outer circumference causing short lifetime
Solution Approach 1:
The patent applies a preventive surface treatment to the outer circumference portion before the susceptor is put into service. By leaving this region unpolished or applying a specific treatment from the beginning, the patent prevents stress concentration and crack initiation that would otherwise occur during repeated use, thereby extending susceptor lifetime without compromising production efficiency.
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 design prevents surface cutting and crack generation, extends susceptor lifetime, ensures stable wafer mounting, and maintains epitaxial layer uniformity without impurity agglomeration, even after repeated use.
Implementation Method 1
a ring-shaped SiC crystal growth surface with a surface roughness Ra in a range of 0.05 μm or more and 3 μm or less
Implementation Method 2
stress is concentrated during the polishing process in the vicinity of a boundary portion between a bottom surface portion of the recess where a semiconductor wafer is mounted on and a vertical portion thereof to cause fine cracks in the film
Implementation Method 3
owing to the thermal stress during the heat treatment, with the fine crack as a starting point, cracks as shown in FIG. 6 are generated on the coated surface
Implementation Method 4
because of the low reactivity and high strength, a SiC member in which SiC is coated on a carbon base material is frequently used
Data Source
AI summary
A susceptor at least a surface thereof being coated with SiC, includes a recess where an wafer is mounted, the recess having an round portion disposed on a lower portion of an outer circumferential portion of the recess, a ring-shaped SiC crystal growth surface portion provided within the round portion in a range of 0.05 mm or more and 0.3 mm or less defined from an outer circumference vertical portion of the recess and a contact portion, where the susceptor contacts with the wafer on the recess, having a surface roughness Ra in a range of 0.5 μm or more and 3 μm or less.