Silicon Etching Composition for Selective Si Over SiO2 Removal
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Solution Overview
Problem
Existing silicon etching processes with 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, limiting 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 a silicon compound, with specific ratios and additives, is used to enhance the selectivity of silicon etching over silicon oxide films, improving the etching process by controlling the etch rates and selectivity through the inclusion of fluorine-based and silicon-based species.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If acidic etchants (containing hydrofluoric acid and nitric acid) are used for silicon etching, then etching capability is improved, but selectivity with respect to silicon oxide film deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by replacing traditional acidic etchants (HF-HNO3 mixture) with a new composition based on ammonium bifluoride, sulfuric acid, and nitrosylsulfuric acid. This parameter change maintains high etching capability while achieving superior selectivity (60 or more) against silicon oxide films, resolving the contradiction between etching capability and selectivity
Solution Approach 2:
The patent creates a composite etching system by combining ammonium bifluoride, sulfuric acid, nitrosylsulfuric acid, and silicon compounds in specific ratios. This composite composition synergistically provides both strong silicon etching capability and high selectivity against silicon oxide, eliminating the need to choose between etching power and selectivity
2Productivity
If non-selective etching of silicon insulating films occurs, then bulk silicon etching is achieved, but lower pattern exposure and short circuits occur
Solution Approach 1:
By changing the chemical composition parameters to ammonium bifluoride-based etchants with controlled concentrations of sulfuric acid and nitrosylsulfuric acid, the patent achieves selective removal of silicon while preserving silicon oxide films, thereby maintaining pattern integrity during bulk etching operations
Solution Approach 2:
The patent introduces nitrosylsulfuric acid as an intermediary substance that mediates the etching reaction to be selective. This intermediary enables the etchant to differentiate between silicon and silicon oxide, allowing bulk silicon removal without damaging the insulating films that define pattern boundaries
3Ease of manufacture
If traditional acidic etchants are used, then etching process is simple, but application in wafer thinning and Through-Silicon Via processes is limited
Solution Approach 1:
The patent modifies the etching solution parameters to create a versatile composition that can be applied across multiple semiconductor processes including wafer thinning and Through-Silicon Via formation. The new ammonium bifluoride-based formulation maintains ease of use while expanding adaptability to advanced semiconductor manufacturing applications
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 film of 60 or more, effectively improving the selective etching ratio and reducing defects in semiconductor processes, thereby enhancing the reliability of silicon etching in semiconductor manufacturing.
Implementation Method 1
a fluorine compound; sulfuric acid; nitrosylsulfuric acid; and a silicon compound
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.