Aluminum Nitride Substrate Scrub Cleaning for Submicron Impurity Removal
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Solution Overview
Problem
The challenge is to effectively remove fine foreign matters from the surface of aluminum nitride single crystal substrates after polishing, as these defects lead to crystal defects during the growth of Al x Ga 1-x N layers due to lattice mismatch, and existing cleaning methods, such as alkaline solutions, risk etching the substrate.
Innovation Solution
A scrub cleaning method using a polymer compound material with a melamine foam resin or similar, absorbed in an alkaline solution with 0.05 to 0.5 wt% potassium or sodium hydroxide, applied in a parallel direction to the substrate surface, combined with citric acid, effectively removes fine foreign matters without etching the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If alkaline solution cleaning is used to remove foreign matters, then cleaning effectiveness is improved, but substrate etching occurs
Solution Approach 1:
The patent changes the concentration parameter of the alkaline solution from conventional high concentrations (1-50 wt% as disclosed in JP 2010-180111 A) to a low concentration range (0.05-0.5 wt%). This parameter change reduces the etching effect on the aluminum nitride substrate while maintaining sufficient cleaning capability for foreign matters, thereby resolving the contradiction between cleaning effectiveness and substrate protection.
2Manufacturing precision
If conventional cleaning methods are used, then processing time is reduced, but fine foreign matters (1 μm or less) remain on substrate
Solution Approach 1:
The patent changes the concentration parameter of the alkaline solution to low concentration (0.05-0.5 wt%), which surprisingly improves the removal of fine foreign matters (1 μm or less) compared to conventional high concentration methods. This parameter optimization achieves better cleaning precision without requiring extended processing time, as the low concentration solution effectively removes fine particles while being gentler on the substrate.
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 significantly reduces the number of foreign matters on the substrate surface, preventing crystal defects and allowing for the growth of high-quality Al x Ga 1-x N layers with reduced micropipes and improved surface smoothness.
Implementation Method 1
an alkaline solution having a concentration of 0.05 to 0.5 wt% of an alkaline which is selected from the group consisting of potassium hydroxide and sodium hydroxide
Implementation Method 2
a polymer compound material which has a lower hardness than the aluminum nitride single crystal and absorbed with the alkaline solution
Implementation Method 3
a polymer compound material which has a lower hardness than the aluminum nitride single crystal and absorbed with the alkaline solution
Data Source
AI summary
[Problem] To provide 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. [Solution] A surface of an aluminum nitride single-crystal substrate is scrubbed 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 an alkali selected from the group consisting of potassium hydroxide and sodium hydroxide, said alkali aqueous solution being absorbed in the polymer compound material.