AlN Etching Composition That Protects Silicon Surface Quality
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Solution Overview
Problem
Existing etching solutions for aluminum nitride (AlN) lack selectivity and tend to cause silicon roughness, with KOH-based solutions becoming cloudy at high temperatures, affecting transparency and consistency, which is detrimental in microelectronic device manufacturing.
Innovation Solution
A cationic surfactant-based etching solution comprising water, a cationic surfactant with a specific structure, a water-miscible organic solvent, and a base, which maintains clarity at elevated temperatures and prevents silicon roughness, offering high etching selectivity and rates for AlN without clouding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If KOH-based etching solution is used to achieve high etching rate and selectivity for AlN, then the etching efficiency is improved, but the solution becomes cloudy at high temperatures reducing transparency and consistency
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by replacing KOH with a specific composition containing ammonium hydroxide (0.1-10% wt), hydrogen peroxide (0.1-10% wt), and water (90-99.8% wt). This parameter change maintains high etching rate for AlN while preventing clouding at elevated temperatures, thus preserving solution transparency and consistency throughout the etching process.
2Manufacturing precision
If highly alkaline wet chemical etching is used to etch AlN selectively, then the etching selectivity is improved, but silicon roughness is caused at the wafer's back-side
Solution Approach 1:
The patent applies local quality by creating directional selectivity in the etching process. The ammonium hydroxide-based solution provides high selectivity for AlN etching while being substantially non-etching to silicon. This localized chemical action etches AlN layers with precision while leaving the silicon substrate surface smooth and unaffected, eliminating the harmful roughness effect.
3Object-affected harmful factors
If non-ionic surfactant such as Triton-X100 is added to prevent silicon roughness, then the silicon surface quality is improved, but the solution turns cloudy at high temperatures
Solution Approach 1:
The patent extracts and eliminates the problematic non-ionic surfactant component from the etching solution formulation. Instead of using Triton-X100 or similar surfactants that cause clouding, the invention uses a surfactant-free ammonium hydroxide-based system. This extraction of the harmful component removes the source of clouding while maintaining smooth silicon surfaces through the inherent selectivity of the ammonium hydroxide chemistry.
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 solution provides high etching selectivity and rates for AlN, maintains a clear composition at high temperatures, and prevents silicon roughness, ensuring consistent and efficient removal of AlN in microelectronic device manufacturing.
Implementation Method 1
a cationic surfactant having a structure represented by Formula A... wherein not all of R1, R2, R3, and R4 are hydrogen
Implementation Method 2
KOH-based solutions were found to etch AlN highly selective to GaN and AlGaN... a base
Data Source
AI summary
Described herein are etching solutions and method of using the etching solutions suitable for etching aluminum nitride (AlN) from a semiconductor substrate during the manufacture of a semiconductor device comprising AlN and silicon material without harming the silicon material. The etching solution comprises a cationic surfactant, water, a base, and a water-miscible organic solvent.