Silicon Etching Composition Selectivity via Nitrosylsulfuric Acid
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Solution Overview
Problem
Existing silicon etching processes using acidic etchants suffer from low selectivity, leading to defects such as exposure of lower patterns and short circuits due to non-selective etching of silicon insulating films like SiO2 and SiN, which limits their application in semiconductor processes like wafer thinning and Through-Silicon Via (TSV).
Innovation Solution
A composition comprising a fluorine compound, sulfuric acid, nitrosylsulfuric acid, and an inorganic acid or its salt, along with a silicon compound, which improves the etching selectivity of silicon over silicon oxide films by controlling the etch rates and oxidizing species concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If acidic etchants containing hydrofluoric acid and nitric acid are used for silicon etching, then etching capability is achieved, but selectivity with respect to silicon oxide film deteriorates resulting in non-selective etching of insulating films
Solution Approach 1:
The patent changes the chemical parameters of the etching composition by replacing nitric acid with nitrosylsulfuric acid and adding specific inorganic acids (phosphoric, hydrochloric, boric, or silicic acid) to achieve high selectivity. The composition ratios are precisely controlled (nitrosylsulfuric acid: 1-30 wt%, inorganic acid: 0.01-15 wt%, fluorine compound: 0.3-30 wt%, sulfuric acid: 50-95 wt%) to optimize the etching behavior and achieve selectivity of 60 or more while maintaining effective silicon etching capability
Solution Approach 2:
The patent creates a composite etching composition by combining multiple chemical components with specific functions: fluorine compounds (for silicon etching), sulfuric acid (as base acid and oxidizing agent), nitrosylsulfuric acid (as primary oxidizing species), and inorganic acids (to control etch rate and enhance selectivity). This composite formulation synergistically achieves both high etching capability and high selectivity, resolving the contradiction between etching effectiveness and selectivity
2Productivity
If conventional acidic etchants are used for bulk etching of silicon, then etching rate is achieved, but selectivity with respect to silicon oxide film deteriorates causing exposure of lower patterns and short circuits
Solution Approach 1:
The patent modifies the chemical composition parameters to achieve high selectivity while maintaining productivity. By using sulfuric acid (50-95 wt%) as the base with controlled oxidizing species concentration through nitrosylsulfuric acid (1-30 wt%), the etching rate is optimized. The addition of inorganic acids further tunes the etch rate to achieve selectivity of 60 or more, ensuring that silicon is etched at a high rate while silicon oxide remains protected
Solution Approach 2:
The patent employs strong oxidizing agents (nitrosylsulfuric acid and sulfuric acid) to create a controlled oxidation environment. The oxidizing species selectively oxidize silicon to form soluble products while the presence of fluorine compounds and inorganic acids prevents excessive oxidation of silicon oxide. This controlled accelerated oxidation enables high etching rates with maintained selectivity, resolving the productivity-selectivity contradiction
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 an etching selectivity of silicon to silicon oxide films of 60 or more, effectively reducing defects and enhancing the etching process by maintaining high oxidizing species concentrations and controlling the etch rates of silicon and silicon oxide films.
Implementation Method 1
a fluorine compound; sulfuric acid; nitrosylsulfuric acid
Implementation Method 2
oxidizing species (typically nitric acid, sulfuric acid, etc.)
Data Source
AI summary
Silicon etching compositions are described and may be used for selectively etching silicon with respect to a silicon insulating film. In particular, the silicon etching compositions can be used to improve the selective etching ratio of silicon from the surface of a semiconductor on which a silicone oxide film and silicon are exposed.