Alternating Plasma Etching for 3D NAND Sidewall Verticality
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Solution Overview
Problem
The existing etching methods for NAND type flash memory devices with three-dimensional structures fail to maintain the verticality of sidewall surfaces when concurrently etching regions with alternately stacked silicon oxide and nitride films and thicker silicon oxide films, leading to deteriorated verticality and potential mask clogging.
Innovation Solution
A method involving alternating generations of plasma using a first processing gas containing fluorocarbon and hydrofluorocarbon gases for etching, followed by a second processing gas with hydrogen, nitrogen, and other gases to reduce hydrogen and deposit carbon/hydrocarbon on sidewalls, protecting the surfaces and preventing mask clogging, thereby improving sidewall verticality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma of a processing gas containing fluorocarbon gas and hydrofluorocarbon gas is generated to etch both regions concurrently, then etching efficiency is improved, but verticality of the sidewall surface deteriorates
Solution Approach 1:
The patent applies periodic action by alternately generating plasma of first processing gas (containing fluorocarbon and hydrofluorocarbon gases) and second processing gas (containing hydrogen, hydrofluorocarbon, and nitrogen gases). The first plasma generation performs etching with high efficiency, while the second plasma generation restores sidewall verticality by reducing hydrogen and depositing carbon/hydrocarbon on the sidewall. This periodic alternation resolves the contradiction by separating the etching function and sidewall protection function into distinct time periods, achieving both high etching efficiency and maintained sidewall verticality throughout the etching process
2Manufacturing precision
If carbon and hydrocarbon are deposited on the sidewall to protect it, then verticality is improved, but mask openings may be clogged
Solution Approach 1:
The patent applies local quality by creating different chemical environments at different locations within the processing chamber. The second processing gas containing hydrogen and nitrogen selectively deposits carbon/hydrocarbon on the sidewall surface while the active species of nitrogen prevents excessive carbon deposition on the mask openings. This localized differentiation of deposition behavior protects the sidewall verticality without causing mask clogging
Solution Approach 2:
The patent applies parameter changes by adjusting the composition of the second processing gas to contain hydrogen, hydrofluorocarbon, and nitrogen gases. The hydrogen reduces excess carbon formation, while the nitrogen provides active species that prevent carbon deposition on mask openings. By changing the gas composition parameters, the system achieves sidewall protection through controlled carbon/hydrocarbon deposition while preventing mask opening clogging
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
This approach enhances the verticality of sidewall surfaces during etching, particularly in the second region, while maintaining high etching throughput by optimizing the processing time for each plasma gas sequence.
Implementation Method 1
generating plasma of a first processing gas containing a fluorocarbon gas and a hydrofluorocarbon gas within a processing vessel
Implementation Method 2
fluorine generated by dissociation of a hydrofluorocarbon gas combines with hydrogen
Implementation Method 3
carbon and/or hydrocarbon generated by the dissociation of the hydrofluorocarbon gas adhere to a sidewall surrounding a space formed by the etching
Implementation Method 4
the amount of the carbon and/or the hydrocarbon deposited on the mask is decreased by active species of nitrogen
Data Source
AI summary
A method of concurrently etching a first region in which silicon oxide films and silicon nitride films are alternately stacked and a second region including the silicon oxide film having a thickness larger than a thickness of the silicon oxide film of the first region is provided. The method includes generating plasma of a first processing gas containing a fluorocarbon gas and a hydrofluorocarbon gas within a processing vessel of a plasma processing apparatus into which a processing target object is carried; and generating plasma of a second processing gas containing a hydrogen gas, a hydrofluorocarbon gas and a nitrogen gas within the processing vessel of the plasma processing apparatus. Further, the generating of the plasma of the first processing gas and the generating of the plasma of the second processing gas are repeated alternately.