Silicon Carbide Substrate Polishing via Oxidant Slurry
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Solution Overview
Problem
The production of silicon carbide single crystal substrates using existing CMP methods often results in surface defects such as concaved and convexed portions or striped step bunching, which hinder the growth of high-quality silicon carbide or gallium nitride semiconductor layers.
Innovation Solution
A method involving CMP with a polishing slurry containing silica abrasive grains and an oxidant, followed by gas phase etching to remove surface residual substances, ensuring a smooth and defect-free surface for epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CMP is performed using only silica slurry, then the surface can be smoothed without causing mechanical distortion, but the polishing rate is very low and it takes a long time
Solution Approach 1:
The patent changes the chemical composition parameters of the polishing slurry by adding oxidants (potassium permanganate, sodium peroxide, hydrogen peroxide, or ozone) to the silica slurry. This chemical parameter change enables the slurry to react with silicon carbide surface, significantly increasing the polishing rate while maintaining the ability to produce smooth surfaces without mechanical distortion
Solution Approach 2:
The patent creates a composite polishing slurry system combining silica abrasive grains with oxidizing agents. The silica provides mechanical polishing action while the oxidants chemically react with the silicon carbide surface, creating a synergistic effect that achieves both high polishing rate and high surface quality
2Ease of manufacture
If diamond abrasive grains are used for mechanical polishing, then the silicon carbide surface can be polished, but tiny scratches and mechanically distorted affected layers are formed
Solution Approach 1:
The patent replaces purely mechanical polishing with a chemically-assisted polishing process. By introducing oxidants that chemically react with the silicon carbide surface to form removable oxides, the method substitutes part of the mechanical action with chemical action, thereby avoiding the scratches and affected layers caused by diamond abrasive grains while still achieving surface smoothing
Solution Approach 2:
The oxidants act as intermediaries between the polishing slurry and the silicon carbide surface. These oxidants chemically transform the silicon carbide surface into oxidized layers that can be easily removed by softer abrasive grains, serving as a mediating substance that enables effective polishing without direct mechanical damage from hard diamond grains
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 yields a silicon carbide single crystal substrate with a mirror-finish surface roughness of 1 nm or less, enabling the formation of high-quality silicon carbide or gallium nitride semiconductor layers without defects, such as striped step bunching.
Implementation Method 1
CMP is a processing technique for polishing a surface of a semiconductor single crystal substrate, by which a target of processing is converted into an oxide or the like using a chemical reaction such as oxidation
Implementation Method 2
gas phase etching to remove surface residual substances
Data Source
Figure 1(a)~1(b)
Figure 2(a)~3
Figure 4(a)~5
AI summary
A method for producing a silicon carbide single crystal substrate according to the present invention includes steps of: (A) preparing a silicon carbide single crystal substrate having a mechanically polished main face; (B) performing chemical mechanical polishing on the main face of the silicon carbide single crystal substrate using a polishing slurry containing abrasive grains dispersed therein to finish the main face as a mirror surface; (C'1) oxidizing at least a part of the main face finished as a mirror surface by a gas phase to form an oxide; and (C'2) removing the oxide.