SiC Substrate Double-Sided CMP Polishing
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Solution Overview
Problem
Conventional CMP polishing methods for SiC substrates face challenges in simultaneously achieving high productivity and yield while effectively removing roughness from both the Si surface and C surface without excessive removal of the epitaxial layer, particularly due to low processing rates and increased costs associated with separate polishing steps.
Innovation Solution
A method employing double-sided CMP polishing with a C surface/Si surface processing selectivity ratio of 3.0 or greater, using a potassium permanganate-based slurry containing alumina as an abrasive, and optimizing polishing conditions to maintain a high polishing rate for the C surface while minimizing epitaxial layer removal, thereby improving planarity and surface quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate polishing steps are used for Si surface and C surface, then polishing quality can be maintained, but processing time and cost increase
Solution Approach 1:
The patent combines the polishing of both Si surface and C surface into a single simultaneous polishing step. The apparatus polishes both surfaces at the same time using a single polishing pad and slurry system, eliminating the need for separate polishing steps and significantly improving processing efficiency while maintaining surface quality
2Productivity
If high polishing rate is used for C surface, then productivity improves, but excessive removal of epitaxial layer occurs
Solution Approach 1:
The patent applies different local conditions to different surfaces during simultaneous polishing. The Si surface receives gentler polishing conditions to protect the epitaxial layer, while the C surface receives more aggressive polishing to remove roughness efficiently. This is achieved through selective slurry application and differential pressure control
Solution Approach 2:
The patent changes polishing parameters such as slurry composition, pH, and oxidation potential to achieve selective polishing rates. By adjusting the slurry's chemical properties, the polishing rate on the C surface is enhanced while the Si surface with epitaxial layer is protected, resolving the contradiction between productivity and precision
3Productivity
If conventional CMP slurry is used, then polishing can be performed, but processing rate is too low for high productivity
Solution Approach 1:
The patent fundamentally changes the slurry parameters by using a strongly oxidizing slurry with pH 2-6 and high oxidation potential. This chemical parameter change dramatically increases the polishing rate on the C surface while maintaining control over the Si surface, achieving both high productivity and effective roughness removal
Solution Approach 2:
The patent employs a strongly oxidizing slurry containing oxidants with high oxidation potential to accelerate the chemical mechanical polishing process. The strong oxidation facilitates faster material removal from the C surface, significantly improving processing rate while the selective application ensures the epitaxial layer on the Si surface remains protected
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 efficient removal of roughness from both surfaces in a single process, maintaining a large epitaxial layer thickness and enhancing surface planarity, thus improving productivity and yield for high-pressure resistant devices.
Implementation Method 1
CMP (Chemical Mechanical Polishing) is a polishing method that has both a chemical action and a mechanical action
Implementation Method 2
The surfaces of the circular disc-shaped SiC substrate are subjected to a grinding treatment using a mechanical grinding method
Implementation Method 3
using a potassium permanganate-based slurry containing alumina as an abrasive
Implementation Method 4
double-sided polishing with a C surface/Si surface processing selectivity ratio of 3.0 or greater
Data Source
AI summary
A method that includes at least a CMP step of subjecting both a Si surface (1a) and a C surface (1b) of an SiC substrate (1) to double-sided polishing using a CMP (Chemical Mechanical Polishing) method with a C surface/Si surface processing selectivity ratio of 3.0 or greater.