SiC Substrate Recovery via Selective Wet Etching
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Solution Overview
Problem
Current silicon carbide substrate recycling methods for HEMT devices are inefficient due to surface contamination and thickness reduction, which affects device performance and is economically costly.
Innovation Solution
A method involving wet etching with a KOH solution, potentially mixed with ethylene glycol and heated, to remove nitrogen-face-polarized gallium nitride layers from carbon-face-polarized silicon carbide substrates, eliminating the need for polishing and grinding, thus preserving substrate thickness and enhancing recycling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mechanical thinning and polishing is used to recycle silicon carbide substrates, then the substrate surface can be restored, but chemical contamination is introduced and substrate thickness is reduced
Solution Approach 1:
The patent replaces the mechanical polishing system with a chemical etching system using KOH solution. The etching process removes the gallium nitride buffer layer and surface contaminants through chemical reaction rather than mechanical abrasion, thereby eliminating the introduction of polishing agent contamination while achieving smooth substrate surface restoration.
Solution Approach 2:
The patent controls the etching depth by adjusting etching parameters such as KOH solution concentration (10%-50%), etching temperature (heated to above 100° C. when ethylene glycol is added), and etching time. By precisely controlling these parameters, the etching process removes only the contaminated surface layer and buffer layer while preserving the bulk substrate thickness.
2Manufacturing precision
If conventional grinding and polishing process is used to recycle silicon carbide substrates, then the substrate surface can be restored, but the thickness of the silicon carbide substrate is reduced
Solution Approach 1:
The patent replaces mechanical grinding and polishing with chemical etching using KOH solution. The etching process selectively removes the gallium nitride buffer layer and surface contaminants through chemical reaction, achieving surface restoration without the material removal associated with mechanical processes, thereby preserving substrate thickness.
Solution Approach 2:
The patent precisely controls the etching depth by adjusting etching parameters including KOH solution concentration (10%-50%), temperature (heated to above 100° C. with ethylene glycol), and etching duration. This parameter control ensures that only the necessary surface layer is removed while maintaining the bulk substrate thickness required for subsequent epitaxial processes.
3Productivity
If wet etching with KOH solution is used to remove epitaxial layers, then the removal speed increases, but the etching process must be carefully controlled to avoid substrate damage
Solution Approach 1:
The patent optimizes etching parameters to achieve high removal speed while maintaining substrate integrity. The KOH solution concentration is set between 10%-50%, and the solution is heated to above 100° C. when ethylene glycol is added, which significantly accelerates the etching rate. Simultaneously, these parameters are controlled to ensure selective etching of gallium nitride layers without damaging the silicon carbide substrate.
Solution Approach 2:
The etching process exhibits selective removal based on material properties. The KOH solution preferentially etches the gallium nitride buffer layer and channel layer while having minimal effect on the silicon carbide substrate. This local selectivity allows rapid removal of epitaxial layers without compromising substrate integrity.
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 method accelerates the removal of epitaxial structures, increases substrate recycling efficiency, and simplifies subsequent epitaxy processes without reducing substrate thickness, thereby improving device performance and reducing economic costs.
Implementation Method 1
removing the nitrogen-face-polarized gallium nitride buffer layer, the barrier layer and the nitrogen-face-polarized gallium nitride channel layer by wet etching
Implementation Method 2
ethylene glycol is added to the KOH solution and the solution is heated to above 100° C.
Implementation Method 3
the epitaxial structure is irradiated with UV light during the wet etching
Implementation Method 4
blowing dry the silicon carbide substrate with a nitrogen gas
Data Source
AI summary
A method for recovering carbon-face-polarized silicon carbide substrates, including: providing an epitaxial structure, the epitaxial structure includes a carbon-face-polarized silicon carbide substrate to be recovered, as well as a nitrogen-face-polarized gallium nitride buffer layer, a barrier layer and a nitrogen-face-polarized gallium nitride channel layer that are sequentially deposited on the silicon carbide substrate; removing the nitrogen-face-polarized gallium nitride buffer layer, the barrier layer and the nitrogen-face-polarized gallium nitride channel layer by wet etching; and cleaning and blowing dry the carbon-face-polarized silicon carbide substrate.