Wet Etching Composition for Si and SiN Substrates
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Solution Overview
Problem
Current wet etching compositions for silicon (Si) films on silicon nitride (SiN) substrates face challenges in achieving high selectivity and efficiency while avoiding corrosion, air pollution, and environmental nitrogen burdens, particularly due to the use of volatile oxidants like nitric acid and inadequate etch rates with alkaline solutions.
Innovation Solution
A wet etching composition comprising 0.1-50% fluorine compounds, 0.04-10% oxidants such as permanganic acid or vanadium pentoxide, and pH adjusters within a pH range of 2.0-5.0, specifically using hydrogen fluoride, potassium fluoride, and pH adjusters like potassium hydroxide, which enhances Si etch rate and selectivity over SiN without generating volatile corrosive components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If concentrated nitric acid is used as an oxidant in wet etching composition, then the etch rate of Si is improved, but nitrogen dioxide is generated causing corrosion of structural members and air pollution
Solution Approach 1:
The patent changes the chemical parameters of the etching composition by replacing concentrated nitric acid with a combination of hydrofluoric acid and potassium permanganate. This substitution maintains the oxidizing function needed for silicon etching while eliminating the generation of nitrogen dioxide, thus resolving the contradiction between etch rate and harmful emissions.
Solution Approach 2:
The patent converts the harmful effect of using strong oxidants into a benefit by selecting potassium permanganate, which provides the necessary oxidizing power for high etch rates while being environmentally benign. The harmful nitrogen dioxide emission is replaced with oxygen-based oxidation that does not produce corrosive or polluting gases.
2Object-generated harmful factors
If potassium permanganate is used as an oxidant instead of nitric acid, then volatile corrosive components are eliminated, but the etch rate of SiN increases reducing selectivity
Solution Approach 1:
The patent optimizes the concentration parameters of hydrofluoric acid (0.1-50 mass%) and potassium permanganate (0.04-10 mass%) to achieve the desired balance. By carefully controlling these parameters, the composition achieves high silicon etch rates while maintaining adequate selectivity against silicon nitride, resolving the contradiction between eliminating harmful emissions and maintaining manufacturing precision.
3Ease of manufacture
If alkaline aqueous solution is used for Si film removal, then the process is simplified, but etch rate greatly differs depending on crystal planes causing incomplete removal
Solution Approach 1:
The patent changes the chemical nature of the etching solution from alkaline to acidic (pH 2.0-5.0) and uses a specific combination of hydrofluoric acid and potassium permanganate. This chemical parameter change enables the etching process to proceed uniformly across different crystal planes of silicon, eliminating the anisotropic etching problem while maintaining process simplicity.
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 composition achieves high Si etch rates with selective removal of Si over SiN, reducing device and exhaust line corrosion and environmental impact, while maintaining effective etching performance.
Implementation Method 1
concentrated nitric acid serves as an oxidant
Implementation Method 2
aqueous solution comprising hydrofluoric acid and concentrated nitric acid
Data Source
AI summary
The present invention relates to a wet etching composition for a substrate having a SiN layer and a Si layer, comprising 0.1-50 mass % fluorine compound (A), 0.04-10 mass % oxidant (B) and water (D) and having pH in a range of 2.0-5.0. The present invention also relates to a wet etching process for a semiconductor substrate having a SiN layer and a Si layer, the process using the wet etching composition. The composition of the present invention can be used for a substrate having a SiN layer and a Si layer to enhance removal selectivity of Si over SiN while reducing corrosion of the device and the exhaust line and air pollution caused by a volatile component generated upon use and further a burden on the environment caused by the nitrogen content contained in the composition.