Etching Method for 3D NAND Multilayer Films
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Solution Overview
Problem
In the manufacturing of NAND type flash memory devices with a three-dimensional structure, existing etching methods struggle to achieve uniform depth and minimize deformation in spaces formed in regions with alternately stacked silicon oxide and silicon nitride films, particularly between the first region with a multilayered film and the second region with a single-layered silicon oxide film.
Innovation Solution
An etching method involving a plasma processing apparatus where a first plasma process with a fluorocarbon and oxygen gas mixture is followed by a second plasma process with a hydrogen, nitrogen trifluoride, hydrogen bromide, and carbon-containing gas mixture, with controlled electrostatic chuck temperatures to optimize etching rates and reduce deformation in both regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single plasma process with fluorocarbon and oxygen gas is used to etch both regions, then the etching rate of the second region (single-layered silicon oxide) is higher, but the deformation degree of the formed space at the bottom portion increases and the depths of spaces in both regions cannot be made substantially equal
Solution Approach 1:
The etching process is divided into two distinct plasma processes: a first plasma process using fluorocarbon and oxygen gas for initial etching, and a second plasma process using hydrogen, nitrogen trifluoride, hydrogen bromide, and carbon-containing gas for final etching. This segmentation allows different etching characteristics to be applied to different regions, enabling depth uniformity and shape control while maintaining high overall etching rate.
Solution Approach 2:
The temperature of the electrostatic chuck is dynamically adjusted between the two plasma processes. The chuck temperature is set to a first temperature in the first plasma process and a second temperature (lower than the first) in the second plasma process. This dynamic temperature adjustment optimizes the etching rate and deformation characteristics for each process stage, resolving the contradiction between productivity and manufacturing precision.
2Manufacturing precision
If the temperature of the electrostatic chuck is increased to reduce mask opening deformation, then the etching rate of the first region (multilayered film) decreases
Solution Approach 1:
The etching process is divided into two distinct plasma processes: a first plasma process using fluorocarbon and oxygen gas for initial etching, and a second plasma process using hydrogen, nitrogen trifluoride, hydrogen bromide, and carbon-containing gas for final etching. This segmentation allows different etching characteristics to be applied to different regions, enabling depth uniformity and shape control while maintaining high overall etching rate.
Solution Approach 2:
The temperature of the electrostatic chuck is dynamically adjusted between the two plasma processes. The chuck temperature is set to a first temperature in the first plasma process and a second temperature (lower than the first) in the second plasma process. This dynamic temperature adjustment optimizes the etching rate and deformation characteristics for each process stage, resolving the contradiction between productivity and manufacturing precision.
3Productivity
If the temperature of the electrostatic chuck is decreased to increase the etching rate of the first region, then the deformation degree of the formed space at the bottom portion increases
Solution Approach 1:
The etching process is divided into two distinct plasma processes: a first plasma process using fluorocarbon and oxygen gas for initial etching, and a second plasma process using hydrogen, nitrogen trifluoride, hydrogen bromide, and carbon-containing gas for final etching. This segmentation allows different etching characteristics to be applied to different regions, enabling depth uniformity and shape control while maintaining high overall etching rate.
Solution Approach 2:
The temperature of the electrostatic chuck is dynamically adjusted between the two plasma processes. The chuck temperature is set to a first temperature in the first plasma process and a second temperature (lower than the first) in the second plasma process. This dynamic temperature adjustment optimizes the etching rate and deformation characteristics for each process stage, resolving the contradiction between productivity and manufacturing precision.
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 ensures that the depths of spaces in both regions become substantially equal and deformation at the bottom portions is minimized, while maintaining a high etching rate, by adjusting the temperature settings for each plasma process.
Implementation Method 1
generating plasma of a first processing gas containing a fluorocarbon gas and an oxygen gas within the processing vessel
Implementation Method 2
generating plasma of a second processing gas containing a hydrogen gas, a nitrogen trifluoride gas, a hydrogen bromide gas and a carbon-containing gas within the processing vessel
Implementation Method 3
mounting the processing target object on an electrostatic chuck provided within a processing vessel of a plasma processing apparatus
Data Source
AI summary
An etching method of etching a first region including a multilayered film, in which silicon oxide films and silicon nitride films are alternately stacked, and a second region including a single-layered silicon oxide film is provided. The etching method includes a first plasma process of generating plasma of a first processing gas containing a fluorocarbon gas and an oxygen gas within a processing vessel of a plasma processing apparatus; and a second plasma process of generating plasma of a second processing gas containing a hydrogen gas, nitrogen trifluoride gas, a hydrogen bromide gas and a carbon-containing gas within the processing vessel. A temperature of an electrostatic chuck is set to a first temperature in the first plasma process, and the temperature of the electrostatic chuck is set to a second temperature lower than the first temperature in the second plasma process.