Aluminum Nitride Substrate Cleaning Without Surface Etching
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Solution Overview
Problem
Existing methods for cleaning aluminum nitride single crystal substrates are ineffective in removing fine foreign matters, leading to crystal defects during the growth of aluminum gallium nitride layers due to lattice mismatch, and alkaline cleaning can etch the substrate, compromising its smoothness.
Innovation Solution
A scrub cleaning method using a polymer compound material with a melamine foam resin or similar, absorbed in an alkaline solution with a concentration of 0.01 to 1 wt % potassium hydroxide or sodium hydroxide, effectively removes foreign matters without etching the substrate, followed by chemical mechanical polishing with colloidal silica.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alkaline cleaning is used to remove fine foreign matters, then cleaning effectiveness improves, but the aluminum nitride substrate surface is etched, compromising smoothness
Solution Approach 1:
The invention precisely controls the pH range (8-14) and composition of alkaline cleaning solutions, and limits cleaning time to 1-60 minutes, to achieve effective foreign matter removal while preventing excessive etching of the aluminum nitride substrate surface
Solution Approach 2:
The invention introduces organic additives (amines, alcohols) as intermediaries in the alkaline cleaning solution to enhance the removal of organic foreign matters while reducing the direct etching effect of pure alkaline solutions on the substrate
2Productivity
If foreign matters remain on the substrate surface, then cleaning is faster and easier, but crystal defects (dislocations and micropipes) are generated during aluminum gallium nitride layer growth
Solution Approach 1:
The invention performs thorough cleaning of the aluminum nitride substrate surface with alkaline solutions before depositing the aluminum gallium nitride layer, removing all foreign matters including fine particles 1 μm or less, to prevent subsequent crystal defects during layer growth
Solution Approach 2:
The invention converts the potential harm of alkaline etching into a benefit by using controlled alkaline cleaning to remove organic contaminants and improve surface wettability, which actually enhances the quality of the subsequent aluminum gallium nitride layer growth
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 method significantly reduces the number of foreign matters on the substrate surface, achieving an ultraflat surface with low crystal defects, enabling the growth of high-quality aluminum gallium nitride layers with reduced micropipes and improved smoothness.
Implementation Method 1
a polymer compound material having a lower hardness than the aluminum nitride single crystal and absorbed with an alkaline solution
Implementation Method 2
a scrub cleaning step wherein a surface of the aluminum nitride single crystal substrate is scrubbed by moving the polymer compound material in a parallel direction of the surface of said substrate
Data Source
AI summary
A method for effectively removing minute impurities of 1 μm or less in size that are present on a surface of an aluminum nitride single-crystal substrate without etching the surface includes scrubbing a surface of an aluminum nitride single-crystal substrate using a polymer compound material having lower hardness than an aluminum nitride single crystal, and an alkali aqueous solution having 0.01-1 mass % concentration of potassium hydroxide or sodium hydroxide, the alkali aqueous solution being absorbed in the polymer compound material.