Silicon Oxide Dry Etching Gas Composition for Low-Temperature Residue Removal
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Solution Overview
Problem
Existing dry etching methods for silicon oxide face issues such as insufficient etching rate, residue formation, and high temperature requirements, leading to reduced productivity and potential damage to non-target parts.
Innovation Solution
A dry etching method using gaseous hydrogen fluoride and an organic amine compound mixture, specifically containing at least two compounds represented by formula (1), allows for high-rate etching of silicon oxide at low temperatures without residue formation, utilizing a non-plasma state and optionally generating low-temperature gas plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional dry etching methods (using HF gas with water vapor, alcohol, or ammonia) are used to etch silicon oxide, then the etching process can be performed without plasma, but the etching rate is insufficient
Solution Approach 1:
The patent changes the chemical parameters of the etching gas composition by introducing organic amine compounds (such as trimethylamine, diethylamine) in combination with HF gas. This chemical parameter change enables significantly higher etching rates while maintaining complete removal of silicon oxide without residues, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent uses a composite gas composition comprising HF gas and organic amine compounds. This composite approach combines the etching capability of HF with the enhanced reactivity provided by organic amines, achieving both high etching rate and complete removal without the limitations of single-component systems.
2Reliability
If ammonium fluorosilicate (AFS) layer is formed using HF and NH3 gas mixture, then silicon oxide can be converted into AFS layer, but heating at temperature higher than 200°C is required to completely remove the AFS layer
Solution Approach 1:
The patent changes the chemical composition parameter from ammonium fluorosilicate (formed with NH3) to organic amine fluorosilicate (formed with organic amine compounds). This parameter change results in a reaction product that can be completely removed at temperatures of 200°C or lower, eliminating the need for high-temperature heating and avoiding heat damage to other parts.
Solution Approach 2:
The organic amine fluorosilicate layer formed in this patent is designed to be easily removable at low temperatures, acting as a temporary layer that is completely eliminated after serving its etching function. This avoids the persistence of AFS layers that require high-temperature removal.
3Reliability
If two-step etching process (COR step followed by PHT step) is used, then silicon oxide can be etched and AFS layer can be removed, but the chamber needs to be heated or cooled every time steps are switched, causing reduction in productivity
Solution Approach 1:
The patent merges the etching step and the residue removal step into a single integrated process. By using organic amine compounds that form easily removable fluorosilicate layers, the etching and cleaning functions are combined into one step performed at low temperature, eliminating the need for separate high-temperature PHT step and the associated heating/cooling cycles.
Solution Approach 2:
The patent enables continuous etching action without interruption for temperature changes. The low-temperature removable fluorosilicate layer allows the etching process to proceed continuously at temperatures of 200°C or lower, maintaining useful action throughout the process without the productivity losses from thermal cycling.
4Reliability
If high temperature heating is applied to remove thick AFS layer, then complete removal can be achieved, but heat damage occurs to parts other than silicon oxide film
Solution Approach 1:
The patent changes the thermal parameter by forming a fluorosilicate layer that is inherently removable at low temperatures through the use of organic amine compounds. This parameter change eliminates the need for high-temperature heating, achieving complete layer removal without exposing other parts to harmful heat effects.
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 method enables efficient etching of silicon oxide at 200°C or lower with enhanced etching rates and selective etching over silicon nitride, reducing residue formation and minimizing heat-induced damage.
Implementation Method 1
the reaction product sublimates at a much lower temperature than ammonium fluorosilicate and thus can be removed at a low temperature
Implementation Method 2
reacting silicon oxide with: gaseous hydrogen fluoride and a gaseous organic amine compound; a hydrogen fluoride salt of a gaseous organic amine compound; or gaseous hydrogen fluoride, a gaseous organic amine compound, and a hydrogen fluoride salt of a gaseous organic amine compound
Data Source
AI summary
A dry etching method including reacting silicon oxide with: gaseous hydrogen fluoride and a gaseous organic amine compound; a hydrogen fluoride salt of a gaseous organic amine compound; or gaseous hydrogen fluoride, a gaseous organic amine compound, and a hydrogen fluoride salt of a gaseous organic amine compound. The organic amine compound is an organic amine mixture containing at least two compounds represented by the following formula (1):R1—N═R2R3 (1)wherein N is a nitrogen atom; R1 is a C1-C10 hydrocarbon group optionally having a ring, a heteroatom, or a halogen atom; R2 and R3 are each a hydrogen atom or a C1-C10 hydrocarbon group optionally having a ring, a heteroatom, or a halogen atom; provided that the hydrocarbon group, when it has a carbon number of 3 or more, may have a branched chain structure or a ring structure.