Silicon Etching Liquid Composition for Smooth Anisotropic Wafer Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing silicon etching technologies face challenges with low etching rates on the 111 plane, leading to pyramid-shaped hillocks and surface roughness, especially when using low alkali concentrations to reduce costs and safety risks, and struggle with high selectivity towards silicon oxide films.
Innovation Solution
A silicon etching liquid comprising quaternary ammonium hydroxide and quaternary ammonium salt, with specific concentrations and carbon atom ranges, is used to suppress hillock formation and enhance selectivity towards silicon oxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low alkali concentration is used to reduce costs and safety risks, then safety and cost improve, but etching rate and surface smoothness deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the etching liquid by introducing quaternary ammonium salts with specific carbon atom counts (6-20) and controlling their concentration (0.1-20 mass%). This parameter change allows the system to achieve high etching rates on silicon 111 planes while maintaining low alkali concentration, thus improving both productivity and safety simultaneously
Solution Approach 2:
The patent creates a composite etching liquid system combining quaternary ammonium hydroxide, quaternary ammonium salts, and water. This composite formulation synergistically enhances etching performance on silicon 111 planes while maintaining low alkali concentration, resolving the contradiction between safety and productivity
2Object-affected harmful factors
If low alkali concentration is used, then safety and cost improve, but surface smoothness and hillock formation deteriorate
Solution Approach 1:
The patent modifies the etching liquid composition by adding quaternary ammonium salts with specific carbon atom ranges (6-20) at controlled concentrations (0.1-20 mass%). This parameter change suppresses hillock formation and maintains surface smoothness even at low alkali concentrations, thereby improving both safety and manufacturing precision
Solution Approach 2:
The quaternary ammonium salts act as molecular templates that replicate favorable etching patterns on silicon surfaces, preventing hillock formation by copying smooth surface structures during the etching process, thus maintaining surface precision under safe operating conditions
3Productivity
If conventional etching liquid is used, then etching capability is maintained, but selectivity with silicon oxide film deteriorates
Solution Approach 1:
The patent changes the chemical composition by incorporating quaternary ammonium salts with specific carbon atom counts (6-20) and optimizing their concentration (0.1-20 mass%). This parameter modification enhances etching selectivity towards silicon oxide films while maintaining high etching capability, allowing simultaneous improvement of productivity and precision
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 enables smooth etching of silicon surfaces with reduced surface roughness and improved selectivity, allowing for efficient processing of silicon wafers and films while minimizing environmental impact and costs.
Implementation Method 1
Silicon etching includes etching with a hydrofluoric acid-nitric acid aqueous solution and etching using alkali
Implementation Method 2
unlike the etching with the hydrofluoric acid-nitric acid aqueous solution, crystal anisotropy is exhibited. Crystal anisotropy refers to nature (etching anisotropy) that brings a difference in etching rate depending on the crystal orientation of silicon
Implementation Method 3
since the hydrofluoric acid-nitric acid aqueous solution oxidizes silicon to produce a silicon oxide film and etches the silicon oxide film
Data Source
AI summary
A silicon etching liquid which is characterized by containing a quaternary ammonium hydroxide represented by formula (1), a quaternary ammonium salt represented by formula (2) and water, and which is also characterized in that the concentration of the quaternary ammonium salt represented by formula (2) is more than 1% by mass but not more than 50% by mass. (1): R1R2R3R4N+·OH− (In formula (1), R1, R2, R3 and R4 may be the same groups or different groups, and each represents an optionally substituted alkyl group, aryl group or a benzyl group.) (2): R5R6R7R8N+·X− (In formula (2), R5, R6, R7 and R8 may be the same groups or different groups, and each represents an optionally substituted alkyl group having from 1 to 16 carbon atoms; and X represents BF4, a fluorine atom, a chlorine atom or a bromine atom.)